Dermatopathology

The Diagnosis: Epidermolysis Bullosa Acquisita  

The diagnosis of epidermolysis bullosa acquisita (EBA) was made based on the clinical and pathologic findings. A blistering disorder that resolves with milia is characteristic of EBA. Hematoxylin and eosin staining demonstrated a pauci-inflammatory separation between the epidermis and dermis (Figure 1). Direct immunofluorescence studies showed linear IgG deposition along the basement membrane zone while C3 was negative (Figure 2). Salt-split skin was essential, as it revealed IgG deposition to the floor of the split (Figure 3), a pattern seen in EBA and not bullous pemphigoid (BP).¹ 

Epidermolysis bullosa acquisita is an acquired autoimmune bullous disorder that results from antibodies to type VII collagen, an anchoring fibril that attaches the lamina densa to the dermis. The epidemiology and etiology of the trigger that leads to antibody production are not well known, but an association between EBA and inflammatory bowel disease has been described.² Although this disease may present in childhood, EBA most commonly is a disorder seen in adults and the elderly. A classic noninflammatory mechanobullous form as well as an inflammatory BP-like form are the most commonly encountered presentations. Light microscopy demonstrates subepidermal cleavage without acantholysis. In the inflammatory BP-like subtype, an inflammatory infiltrate may be present. Direct immunofluorescence is remarkable for a linear band of IgG deposits along the basement membrane zone, with or without C3 deposition in a similar pattern.¹ 

Bullous pemphigoid is within the differential of EBA. It can be difficult to differentiate clinically, especially when a patient has the BP-like variant of EBA because, as the name implies, it mimics BP. Patients with BP often will report a pruritic patch that will then develop into an urticarial plaque. Scarring and milia rarely are seen in BP but can be observed in the multiple presentations of EBA. Hematoxylin and eosin staining and direct immunofluorescence may be almost identical, and differentiating between the 2 disorders can be a challenge. Immunodeposition in EBA occurs in a U-shaped, serrated pattern, while the pattern in BP is N-shaped and serrated.³ Although the U-shaped, serrated pattern is relatively specific, it is not always easy to interpret and requires a high-quality biopsy specimen, which can be difficult to discern with certainty in suboptimal preparations. Another way to differentiate between the 2 entities is to utilize the salt-split skin technique, as performed in our patient. With salt-split skin, the biopsy is placed into a solution of 1 mol/L sodium chloride and incubated at 4 °C (39 °F) for 18 to 24 hours. A blister is then produced at the level of the lamina lucida, which allows for the staining of immunoreactants to occur either above or below that split (commonly referred to as staining on the roof or floor of the blister cavity). With EBA, there is immunoreactant deposition on the floor of the blister, while the opposite occurs in BP.⁴ 

Epidermolysis bullosa simplex is the most common type of epidermolysis bullosa, with keratin genes KRT5 and KRT14 as frequent mutations. Patients develop blisters, vesicles, bullae, and milia on traumatized areas of the body such as the hands, elbows, knees, and feet. This disease presents early in childhood. Histology exhibits a cell-poor subepidermal blister.⁵ With porphyria cutanea tarda, reduced activity of uroporphyrinogen decarboxylase, a major enzyme in the heme synthesis pathway, leads to blisters with erosions and milia on sun-exposed areas of the body. Histologic evaluation reveals a subepidermal pauci-inflammatory vesicle with festooning of the dermal papillae and amphophilic basement membrane within the epidermis. Direct immunofluorescence of porphyria cutanea tarda demonstrates IgM and C3 in the vessels.⁶ Sweet syndrome is a neutrophilic dermatosis that presents as erythematous, edematous, hot, and tender plaques along with fever and leukocytosis. It is associated with myeloproliferative disorders. Biopsy demonstrates papillary dermal edema along with diffuse neutrophilic infiltrate.⁷ 

Numerous medications have been recommended for the treatment of EBA, ranging from steroids to steroid-sparing drugs such as colchicine and dapsone.^8,9 Our patient was educated on physical precautions and was started on dapsone alone due to comorbid diabetes mellitus and renal disease. Within a few weeks of initiating dapsone, he observed a reduction in erythema, and within months he experienced a decrease in blister eruption frequency.  

The Diagnosis: Epidermolysis Bullosa Acquisita  

The diagnosis of epidermolysis bullosa acquisita (EBA) was made based on the clinical and pathologic findings. A blistering disorder that resolves with milia is characteristic of EBA. Hematoxylin and eosin staining demonstrated a pauci-inflammatory separation between the epidermis and dermis (Figure 1). Direct immunofluorescence studies showed linear IgG deposition along the basement membrane zone while C3 was negative (Figure 2). Salt-split skin was essential, as it revealed IgG deposition to the floor of the split (Figure 3), a pattern seen in EBA and not bullous pemphigoid (BP).¹ 

Epidermolysis bullosa acquisita is an acquired autoimmune bullous disorder that results from antibodies to type VII collagen, an anchoring fibril that attaches the lamina densa to the dermis. The epidemiology and etiology of the trigger that leads to antibody production are not well known, but an association between EBA and inflammatory bowel disease has been described.² Although this disease may present in childhood, EBA most commonly is a disorder seen in adults and the elderly. A classic noninflammatory mechanobullous form as well as an inflammatory BP-like form are the most commonly encountered presentations. Light microscopy demonstrates subepidermal cleavage without acantholysis. In the inflammatory BP-like subtype, an inflammatory infiltrate may be present. Direct immunofluorescence is remarkable for a linear band of IgG deposits along the basement membrane zone, with or without C3 deposition in a similar pattern.¹ 

Bullous pemphigoid is within the differential of EBA. It can be difficult to differentiate clinically, especially when a patient has the BP-like variant of EBA because, as the name implies, it mimics BP. Patients with BP often will report a pruritic patch that will then develop into an urticarial plaque. Scarring and milia rarely are seen in BP but can be observed in the multiple presentations of EBA. Hematoxylin and eosin staining and direct immunofluorescence may be almost identical, and differentiating between the 2 disorders can be a challenge. Immunodeposition in EBA occurs in a U-shaped, serrated pattern, while the pattern in BP is N-shaped and serrated.³ Although the U-shaped, serrated pattern is relatively specific, it is not always easy to interpret and requires a high-quality biopsy specimen, which can be difficult to discern with certainty in suboptimal preparations. Another way to differentiate between the 2 entities is to utilize the salt-split skin technique, as performed in our patient. With salt-split skin, the biopsy is placed into a solution of 1 mol/L sodium chloride and incubated at 4 °C (39 °F) for 18 to 24 hours. A blister is then produced at the level of the lamina lucida, which allows for the staining of immunoreactants to occur either above or below that split (commonly referred to as staining on the roof or floor of the blister cavity). With EBA, there is immunoreactant deposition on the floor of the blister, while the opposite occurs in BP.⁴ 

Epidermolysis bullosa simplex is the most common type of epidermolysis bullosa, with keratin genes KRT5 and KRT14 as frequent mutations. Patients develop blisters, vesicles, bullae, and milia on traumatized areas of the body such as the hands, elbows, knees, and feet. This disease presents early in childhood. Histology exhibits a cell-poor subepidermal blister.⁵ With porphyria cutanea tarda, reduced activity of uroporphyrinogen decarboxylase, a major enzyme in the heme synthesis pathway, leads to blisters with erosions and milia on sun-exposed areas of the body. Histologic evaluation reveals a subepidermal pauci-inflammatory vesicle with festooning of the dermal papillae and amphophilic basement membrane within the epidermis. Direct immunofluorescence of porphyria cutanea tarda demonstrates IgM and C3 in the vessels.⁶ Sweet syndrome is a neutrophilic dermatosis that presents as erythematous, edematous, hot, and tender plaques along with fever and leukocytosis. It is associated with myeloproliferative disorders. Biopsy demonstrates papillary dermal edema along with diffuse neutrophilic infiltrate.⁷ 

Numerous medications have been recommended for the treatment of EBA, ranging from steroids to steroid-sparing drugs such as colchicine and dapsone.^8,9 Our patient was educated on physical precautions and was started on dapsone alone due to comorbid diabetes mellitus and renal disease. Within a few weeks of initiating dapsone, he observed a reduction in erythema, and within months he experienced a decrease in blister eruption frequency.  

The Diagnosis: Epidermolysis Bullosa Acquisita  

The diagnosis of epidermolysis bullosa acquisita (EBA) was made based on the clinical and pathologic findings. A blistering disorder that resolves with milia is characteristic of EBA. Hematoxylin and eosin staining demonstrated a pauci-inflammatory separation between the epidermis and dermis (Figure 1). Direct immunofluorescence studies showed linear IgG deposition along the basement membrane zone while C3 was negative (Figure 2). Salt-split skin was essential, as it revealed IgG deposition to the floor of the split (Figure 3), a pattern seen in EBA and not bullous pemphigoid (BP).¹ 

Epidermolysis bullosa acquisita is an acquired autoimmune bullous disorder that results from antibodies to type VII collagen, an anchoring fibril that attaches the lamina densa to the dermis. The epidemiology and etiology of the trigger that leads to antibody production are not well known, but an association between EBA and inflammatory bowel disease has been described.² Although this disease may present in childhood, EBA most commonly is a disorder seen in adults and the elderly. A classic noninflammatory mechanobullous form as well as an inflammatory BP-like form are the most commonly encountered presentations. Light microscopy demonstrates subepidermal cleavage without acantholysis. In the inflammatory BP-like subtype, an inflammatory infiltrate may be present. Direct immunofluorescence is remarkable for a linear band of IgG deposits along the basement membrane zone, with or without C3 deposition in a similar pattern.¹ 

Bullous pemphigoid is within the differential of EBA. It can be difficult to differentiate clinically, especially when a patient has the BP-like variant of EBA because, as the name implies, it mimics BP. Patients with BP often will report a pruritic patch that will then develop into an urticarial plaque. Scarring and milia rarely are seen in BP but can be observed in the multiple presentations of EBA. Hematoxylin and eosin staining and direct immunofluorescence may be almost identical, and differentiating between the 2 disorders can be a challenge. Immunodeposition in EBA occurs in a U-shaped, serrated pattern, while the pattern in BP is N-shaped and serrated.³ Although the U-shaped, serrated pattern is relatively specific, it is not always easy to interpret and requires a high-quality biopsy specimen, which can be difficult to discern with certainty in suboptimal preparations. Another way to differentiate between the 2 entities is to utilize the salt-split skin technique, as performed in our patient. With salt-split skin, the biopsy is placed into a solution of 1 mol/L sodium chloride and incubated at 4 °C (39 °F) for 18 to 24 hours. A blister is then produced at the level of the lamina lucida, which allows for the staining of immunoreactants to occur either above or below that split (commonly referred to as staining on the roof or floor of the blister cavity). With EBA, there is immunoreactant deposition on the floor of the blister, while the opposite occurs in BP.⁴ 

Epidermolysis bullosa simplex is the most common type of epidermolysis bullosa, with keratin genes KRT5 and KRT14 as frequent mutations. Patients develop blisters, vesicles, bullae, and milia on traumatized areas of the body such as the hands, elbows, knees, and feet. This disease presents early in childhood. Histology exhibits a cell-poor subepidermal blister.⁵ With porphyria cutanea tarda, reduced activity of uroporphyrinogen decarboxylase, a major enzyme in the heme synthesis pathway, leads to blisters with erosions and milia on sun-exposed areas of the body. Histologic evaluation reveals a subepidermal pauci-inflammatory vesicle with festooning of the dermal papillae and amphophilic basement membrane within the epidermis. Direct immunofluorescence of porphyria cutanea tarda demonstrates IgM and C3 in the vessels.⁶ Sweet syndrome is a neutrophilic dermatosis that presents as erythematous, edematous, hot, and tender plaques along with fever and leukocytosis. It is associated with myeloproliferative disorders. Biopsy demonstrates papillary dermal edema along with diffuse neutrophilic infiltrate.⁷ 

Numerous medications have been recommended for the treatment of EBA, ranging from steroids to steroid-sparing drugs such as colchicine and dapsone.^8,9 Our patient was educated on physical precautions and was started on dapsone alone due to comorbid diabetes mellitus and renal disease. Within a few weeks of initiating dapsone, he observed a reduction in erythema, and within months he experienced a decrease in blister eruption frequency.  

Amyloidosis consists of approximately 30 protein-folding disorders sharing the common feature of abnormal extracellular amyloid deposition. In each condition, a specific soluble precursor protein aggregates to form the insoluble fibrils of amyloid, characterized by the beta-pleated sheet structure.¹ Amyloidosis occurs as either a systemic or localized process. Insulin-derived (AIns) amyloidosis, a localized process occurring at insulin injection sites, was first reported in 1983.² There were fewer than 20 reported cases until 2014, when 57 additional cases were reported by just 2 institutions,^3,4 indicating that AIns amyloidosis may be more common than previously thought.^3,5

Despite the increasing prevalence of diabetes mellitus and insulin use, there is a paucity of published cases of AIns amyloidosis. The lack of awareness of this condition among both dermatologists and general practitioners may be in part due to its variable clinical manifestations. We describe 2 patients with unique presentations of localized amyloidosis at repeated insulin injection sites.

Case Reports

Patient 1
A 39-year-old man with a history of type 1 diabetes mellitus presented with 4 asymptomatic nodules on the lateral thighs in areas of previous insulin injection. He first noticed the lesions 9 months prior to presentation and subsequently switched the injection site to the abdomen without development of new nodules. Despite being compliant with his insulin regimen, he had a long history of irregular glucose control, including frequent hypoglycemic episodes. The patient was using regular and neutral protamine hagedorn insulin.

On physical examination, 2 soft, nontender, exophytic nodules were noted on each upper thigh with surrounding hyperpigmented and hyperkeratotic collarettes (Figure 1). The nodules ranged in size from 2 to 3.5 cm in diameter.

Patient 2
A 53-year-old woman with a history of type 2 diabetes mellitus presented with painful subcutaneous nodules on the lower abdomen at sites of previous insulin injections. The nodules developed approximately 1 month after she started treatment with neutral protamine hagedorn insulin and had been slowly enlarging over the past year. She tried switching injection sites after noticing the lesions, but the nodules persisted. The patient had a long history of poor glucose control with chronically elevated glycohemoglobin and blood glucose levels.

On physical examination, 2 hyperpigmented, exophytic, smooth nodules were noted on the right and left lower abdomen, ranging in size from 2.5 to 5.5 cm in diameter (Figure 4).

Comment

Insulin is the suspected precursor protein in AIns amyloidosis, but the exact pathogenesis is unknown. The protein that is derived from insulin in these tumors is now identified as AIns amyloidosis.^5,6 It is hypothesized that insulin accumulates locally and is converted to amyloid by an unknown mechanism.⁷ Other potential contributory factors include chronic inflammation and foreign body reactions developing around amyloid deposits, as well as repeated trauma from injections into a single site.^4,5 It appears that lesions may derive from a wide range of insulin types and occur after variable time periods.

A majority of cases of iatrogenic amyloid have been described as single, firm, subcutaneous masses at an injection site that commonly are misdiagnosed as lipomas or lipohypertrophy.^7-11 To our knowledge, none of the reported cases resembled the multiple, discrete, exophytic nodules seen in our patients.^3,4 The surrounding hyperkeratosis noted in patient 1 is another uncommon feature of AIns amyloidosis (Figures 1 and 2). Only 3 AIns amyloidosis cases described lesions with acanthosis nigricans–like changes, only 1 of which provided a clinical image.^6,7,12The mechanism for the acanthosis nigricans–like changes may have been due to the high levels of insulin at the injection site. It has been suggested that the activation of insulinlike growth factor receptor by insulin leads to the proliferation of keratinocytes and fibroblasts.⁶ Histologic examination of AIns amyloidosis lesions generally demonstrates deposition of homogenous eosinophilic material consistent with amyloid, as well as positive Congo red staining with green birefringence by polarization. Immunohistologic staining with insulin antibody with or without proteomic analysis of the amyloid deposits can confirm the diagnosis. In both of our patients’ specimens, liquid chromatography–tandem mass spectrometry was performed for proteomic analysis, and results were consistent with AIns amyloidosis.

Reports in the literature have suggested that the deposition of amyloid at insulin injection sites has the potential to interfere with insulin absorption, leading to poor glucose control.^4,11,13 Hence, injection site rotation is a crucial aspect of treatment and prevention of AIns amyloidosis. In their study of 4 patients, Nagase et al⁴ compared serum insulin levels after insulin injection into amyloid nodules vs insulin levels after injection into normal skin. Insulin absorption at the amyloid sites was 34% of that at normal sites. Given these results, patients should be instructed to inject away from the amyloid deposit once it is identified.⁶ Glucose levels should be monitored closely when patients first inject away from the amyloid mass, as injection of the same dosage to an area of normal skin can lead to increased insulin absorption and hypoglycemia.^4,6 It is possible that the frequent hypoglycemic episodes noted in patient 1 were due to increased insulin sensitivity after switching to injection sites away from amyloid lesions.

Conclusion

Our patients demonstrate unique presentations of localized cutaneous amyloidosis at repeated insulin injection sites. We report these cases to complement the current data of iatrogenic amyloidosis and provide insight into this likely underreported phenomenon.

Amyloidosis consists of approximately 30 protein-folding disorders sharing the common feature of abnormal extracellular amyloid deposition. In each condition, a specific soluble precursor protein aggregates to form the insoluble fibrils of amyloid, characterized by the beta-pleated sheet structure.¹ Amyloidosis occurs as either a systemic or localized process. Insulin-derived (AIns) amyloidosis, a localized process occurring at insulin injection sites, was first reported in 1983.² There were fewer than 20 reported cases until 2014, when 57 additional cases were reported by just 2 institutions,^3,4 indicating that AIns amyloidosis may be more common than previously thought.^3,5

Despite the increasing prevalence of diabetes mellitus and insulin use, there is a paucity of published cases of AIns amyloidosis. The lack of awareness of this condition among both dermatologists and general practitioners may be in part due to its variable clinical manifestations. We describe 2 patients with unique presentations of localized amyloidosis at repeated insulin injection sites.

Case Reports

Patient 1
A 39-year-old man with a history of type 1 diabetes mellitus presented with 4 asymptomatic nodules on the lateral thighs in areas of previous insulin injection. He first noticed the lesions 9 months prior to presentation and subsequently switched the injection site to the abdomen without development of new nodules. Despite being compliant with his insulin regimen, he had a long history of irregular glucose control, including frequent hypoglycemic episodes. The patient was using regular and neutral protamine hagedorn insulin.

On physical examination, 2 soft, nontender, exophytic nodules were noted on each upper thigh with surrounding hyperpigmented and hyperkeratotic collarettes (Figure 1). The nodules ranged in size from 2 to 3.5 cm in diameter.

Patient 2
A 53-year-old woman with a history of type 2 diabetes mellitus presented with painful subcutaneous nodules on the lower abdomen at sites of previous insulin injections. The nodules developed approximately 1 month after she started treatment with neutral protamine hagedorn insulin and had been slowly enlarging over the past year. She tried switching injection sites after noticing the lesions, but the nodules persisted. The patient had a long history of poor glucose control with chronically elevated glycohemoglobin and blood glucose levels.

On physical examination, 2 hyperpigmented, exophytic, smooth nodules were noted on the right and left lower abdomen, ranging in size from 2.5 to 5.5 cm in diameter (Figure 4).

Comment

Insulin is the suspected precursor protein in AIns amyloidosis, but the exact pathogenesis is unknown. The protein that is derived from insulin in these tumors is now identified as AIns amyloidosis.^5,6 It is hypothesized that insulin accumulates locally and is converted to amyloid by an unknown mechanism.⁷ Other potential contributory factors include chronic inflammation and foreign body reactions developing around amyloid deposits, as well as repeated trauma from injections into a single site.^4,5 It appears that lesions may derive from a wide range of insulin types and occur after variable time periods.

A majority of cases of iatrogenic amyloid have been described as single, firm, subcutaneous masses at an injection site that commonly are misdiagnosed as lipomas or lipohypertrophy.^7-11 To our knowledge, none of the reported cases resembled the multiple, discrete, exophytic nodules seen in our patients.^3,4 The surrounding hyperkeratosis noted in patient 1 is another uncommon feature of AIns amyloidosis (Figures 1 and 2). Only 3 AIns amyloidosis cases described lesions with acanthosis nigricans–like changes, only 1 of which provided a clinical image.^6,7,12The mechanism for the acanthosis nigricans–like changes may have been due to the high levels of insulin at the injection site. It has been suggested that the activation of insulinlike growth factor receptor by insulin leads to the proliferation of keratinocytes and fibroblasts.⁶ Histologic examination of AIns amyloidosis lesions generally demonstrates deposition of homogenous eosinophilic material consistent with amyloid, as well as positive Congo red staining with green birefringence by polarization. Immunohistologic staining with insulin antibody with or without proteomic analysis of the amyloid deposits can confirm the diagnosis. In both of our patients’ specimens, liquid chromatography–tandem mass spectrometry was performed for proteomic analysis, and results were consistent with AIns amyloidosis.

Reports in the literature have suggested that the deposition of amyloid at insulin injection sites has the potential to interfere with insulin absorption, leading to poor glucose control.^4,11,13 Hence, injection site rotation is a crucial aspect of treatment and prevention of AIns amyloidosis. In their study of 4 patients, Nagase et al⁴ compared serum insulin levels after insulin injection into amyloid nodules vs insulin levels after injection into normal skin. Insulin absorption at the amyloid sites was 34% of that at normal sites. Given these results, patients should be instructed to inject away from the amyloid deposit once it is identified.⁶ Glucose levels should be monitored closely when patients first inject away from the amyloid mass, as injection of the same dosage to an area of normal skin can lead to increased insulin absorption and hypoglycemia.^4,6 It is possible that the frequent hypoglycemic episodes noted in patient 1 were due to increased insulin sensitivity after switching to injection sites away from amyloid lesions.

Conclusion

Our patients demonstrate unique presentations of localized cutaneous amyloidosis at repeated insulin injection sites. We report these cases to complement the current data of iatrogenic amyloidosis and provide insight into this likely underreported phenomenon.

Amyloidosis consists of approximately 30 protein-folding disorders sharing the common feature of abnormal extracellular amyloid deposition. In each condition, a specific soluble precursor protein aggregates to form the insoluble fibrils of amyloid, characterized by the beta-pleated sheet structure.¹ Amyloidosis occurs as either a systemic or localized process. Insulin-derived (AIns) amyloidosis, a localized process occurring at insulin injection sites, was first reported in 1983.² There were fewer than 20 reported cases until 2014, when 57 additional cases were reported by just 2 institutions,^3,4 indicating that AIns amyloidosis may be more common than previously thought.^3,5

Despite the increasing prevalence of diabetes mellitus and insulin use, there is a paucity of published cases of AIns amyloidosis. The lack of awareness of this condition among both dermatologists and general practitioners may be in part due to its variable clinical manifestations. We describe 2 patients with unique presentations of localized amyloidosis at repeated insulin injection sites.

Case Reports

Patient 1
A 39-year-old man with a history of type 1 diabetes mellitus presented with 4 asymptomatic nodules on the lateral thighs in areas of previous insulin injection. He first noticed the lesions 9 months prior to presentation and subsequently switched the injection site to the abdomen without development of new nodules. Despite being compliant with his insulin regimen, he had a long history of irregular glucose control, including frequent hypoglycemic episodes. The patient was using regular and neutral protamine hagedorn insulin.

On physical examination, 2 soft, nontender, exophytic nodules were noted on each upper thigh with surrounding hyperpigmented and hyperkeratotic collarettes (Figure 1). The nodules ranged in size from 2 to 3.5 cm in diameter.

Patient 2
A 53-year-old woman with a history of type 2 diabetes mellitus presented with painful subcutaneous nodules on the lower abdomen at sites of previous insulin injections. The nodules developed approximately 1 month after she started treatment with neutral protamine hagedorn insulin and had been slowly enlarging over the past year. She tried switching injection sites after noticing the lesions, but the nodules persisted. The patient had a long history of poor glucose control with chronically elevated glycohemoglobin and blood glucose levels.

On physical examination, 2 hyperpigmented, exophytic, smooth nodules were noted on the right and left lower abdomen, ranging in size from 2.5 to 5.5 cm in diameter (Figure 4).

Comment

Insulin is the suspected precursor protein in AIns amyloidosis, but the exact pathogenesis is unknown. The protein that is derived from insulin in these tumors is now identified as AIns amyloidosis.^5,6 It is hypothesized that insulin accumulates locally and is converted to amyloid by an unknown mechanism.⁷ Other potential contributory factors include chronic inflammation and foreign body reactions developing around amyloid deposits, as well as repeated trauma from injections into a single site.^4,5 It appears that lesions may derive from a wide range of insulin types and occur after variable time periods.

A majority of cases of iatrogenic amyloid have been described as single, firm, subcutaneous masses at an injection site that commonly are misdiagnosed as lipomas or lipohypertrophy.^7-11 To our knowledge, none of the reported cases resembled the multiple, discrete, exophytic nodules seen in our patients.^3,4 The surrounding hyperkeratosis noted in patient 1 is another uncommon feature of AIns amyloidosis (Figures 1 and 2). Only 3 AIns amyloidosis cases described lesions with acanthosis nigricans–like changes, only 1 of which provided a clinical image.^6,7,12The mechanism for the acanthosis nigricans–like changes may have been due to the high levels of insulin at the injection site. It has been suggested that the activation of insulinlike growth factor receptor by insulin leads to the proliferation of keratinocytes and fibroblasts.⁶ Histologic examination of AIns amyloidosis lesions generally demonstrates deposition of homogenous eosinophilic material consistent with amyloid, as well as positive Congo red staining with green birefringence by polarization. Immunohistologic staining with insulin antibody with or without proteomic analysis of the amyloid deposits can confirm the diagnosis. In both of our patients’ specimens, liquid chromatography–tandem mass spectrometry was performed for proteomic analysis, and results were consistent with AIns amyloidosis.

Reports in the literature have suggested that the deposition of amyloid at insulin injection sites has the potential to interfere with insulin absorption, leading to poor glucose control.^4,11,13 Hence, injection site rotation is a crucial aspect of treatment and prevention of AIns amyloidosis. In their study of 4 patients, Nagase et al⁴ compared serum insulin levels after insulin injection into amyloid nodules vs insulin levels after injection into normal skin. Insulin absorption at the amyloid sites was 34% of that at normal sites. Given these results, patients should be instructed to inject away from the amyloid deposit once it is identified.⁶ Glucose levels should be monitored closely when patients first inject away from the amyloid mass, as injection of the same dosage to an area of normal skin can lead to increased insulin absorption and hypoglycemia.^4,6 It is possible that the frequent hypoglycemic episodes noted in patient 1 were due to increased insulin sensitivity after switching to injection sites away from amyloid lesions.

Conclusion

Our patients demonstrate unique presentations of localized cutaneous amyloidosis at repeated insulin injection sites. We report these cases to complement the current data of iatrogenic amyloidosis and provide insight into this likely underreported phenomenon.

The Diagnosis: Subcutaneous Panniculitislike T-cell Lymphoma 

Subcutaneous panniculitislike T-cell lymphoma (SPTCL) is a rare form of cutaneous lymphoma of mature cytotoxic T cells simulating panniculitis and preferentially infiltrating the subcutaneous tissue.¹ Subcutaneous panniculitislike T-cell lymphoma can affect all ages but predominantly affects younger individuals, with 20% being younger than 20 years.² It is a rare lymphoma that accounts for less than 1% of all non-Hodgkin lymphomas.³ It presents clinically as multiple subcutaneous masses, nodules, or plaques generally on the trunk or extremities.^1,2 The skin surrounding the nodules may be erythematous, and the nodules may become necrotic; however, ulceration typically is not seen. Systemic symptoms such as fever, night sweats, and chills are present in half of cases.¹ According to the World Health Organization, cytopenia and elevated liver function tests are common, and a hemophagocytic syndrome may be present in 15% to 20% of cases.³ The presence of a hemophagocytic syndrome yields a poor prognosis.^1,3 Current guidelines denote that SPTCL T-cell receptor (TCR) αβ; is a distinct entity from the TCRγδ; phenotype, known as cutaneous γδ-positive T-cell lymphoma.^3,4 Cutaneous γδ-positive T-cell lymphoma is associated with rapid decline and a worse prognosis.⁴  

Histology of SPTCL is characteristic for a lobular panniculitislike infiltrate.¹ The heavy subcutaneous lymphoid infiltrate is composed of atypical small- to medium-sized lymphocytes with mature chromatin and inconspicuous nucleoli lining adipocytes. The dense inflammatory infiltrate composed predominantly of neoplastic T cells and macrophages may diffusely invade into the subcutaneous tissue.¹ Admixed histocytes and karyorrhectic debris as well as rimming of the lymphocytes around the fat cells is typical and was seen in our patient (quiz image). The T cells of SPTCL have the following immunophenotype: TCR-beta F1⁺, CD3⁺, CD4^-, CD8⁺, CD56^-. They can express numerous cytotoxic proteins, such as T1a-1, granzyme B, and perforin.^2,3 Although the CD8⁺ T cells may be sparse, they generally surround the adipocytes in a rimming manner and may distort the adipocyte membrane.¹  

Lupus erythematosus profundus (LEP) is a form of chronic cutaneous lupus that affects the deep dermis and fat.⁵ It also can present clinically as tender plaques or nodules. It most frequently involves the upper arms, shoulders, face, or buttocks--areas that are less commonly involved in other panniculitides.⁶ Histologically, LEP is similar to chronic discoid lupus with features such as epidermal atrophy, interface changes, and a thickened basement membrane (Figure 1). Lupus erythematosus profundus can present as a lobular panniculitis with mucin as well as a superficial and deep lymphocytic infiltrate that can involve the septa.⁵ Some cases of LEP have a predominantly lobular lymphocytic panniculitis in the absence of the typical epidermal or dermal changes of lupus erythematosus. Lymphoid follicles with germinal center formation are present in half of cases and reportedly are characteristic of LEP.^6,7 The lymphoid follicles often have plasma cells, can extend into the septa as well as in between collagen bundles, and may have nuclear fragmentation.⁵ Another characteristic feature of LEP is hyaline sclerosis of lobules with focal extension into the interlobular septa. Immunofluorescence studies usually show linear deposition of IgM and C3 at the dermoepidermal junction. Antinuclear antibodies can be present in patients who have LEP but are not entirely specific.⁶  

Lupus erythematosus profundus and SPTCL are part of a spectrum and may have overlapping clinical and histopathologic characteristics; therefore, distinguishing them may be difficult.^6-8 It is important to monitor these patients closely, as their disease may progress to lymphoma.⁶ Patients with SPTCL are more likely to present with advanced symptoms such as fever and hepatosplenomegaly and to succumb to hemophagocytic syndrome than patients with LEP.⁹  

Although SPTCL usually is clonal, several cases of LEP with clonality also have been described. Clonal LEP cases generally are identified in patients who present with fever and cytopenia.⁸ Lymphoid atypia and morphologic abnormalities may be seen in cases of LEP, further complicating the distinction between LEP and SPTCL. An elevated Ki67 level may be seen in cases of SPTCL with periadipocytic rimming.⁹ LeBlanc et al¹⁰ used Ki67 "hot spots" along with CD8 immunohistochemistry to identify atypical lymphocytes associated with SPTCL. Lymphocyte rimming was defined by the presence of CD8⁺ lymphocytes with an elevated Ki67 index. Clinical, histopathologic, and molecular findings all should be used when dealing with challenging cases.  

Fat necrosis can occur in any part of the body where trauma has occurred and can be associated with many disease processes. Patients typically present with a palpable mass, but a clinical history of trauma is not always present. Histopathologic findings include necrotic fat alongside lipid-laden foamy macrophages and scattered inflammatory cells (Figure 2).¹¹ Fragments of normal as well as degenerating adipose tissue and multinucleated giant cells can be present.  

Erythema nodosum (EN) is the most frequently encountered panniculitis and usually is seen in women in early adulthood.¹² Patients present with several tender subcutaneous nodules and plaques that most commonly are present on the anterior surface of the legs.^12,13 Patients may have a constellation of symptoms including fever and leukocytosis, but the disorder generally is self-limited.¹² Erythema nodosum may be associated with a variety of diseases or infections including sarcoidosis, inflammatory bowel disease, and malignancy.¹⁴ The etiology of EN is diverse; therefore, a proper clinical workup may be necessary. Histopathology is that of a septal panniculitis with lymphocytes, histiocytes, and occasional eosinophils (Figure 3).¹³  

Lipodermatosclerosis also occurs on the legs, most commonly in patients with venous insufficiency.^12,15 Patients present clinically with pain, induration, redness, or swelling of the legs. Histopathology predominantly is characterized by membranous fat necrosis, fibrosis, and fatty microcysts that may be lined by a thickened hyaline membrane (Figure 4). Lipodermatosclerosis lesions generally do not resolve spontaneously and may need to be treated.¹⁶ 

The Diagnosis: Subcutaneous Panniculitislike T-cell Lymphoma 

Subcutaneous panniculitislike T-cell lymphoma (SPTCL) is a rare form of cutaneous lymphoma of mature cytotoxic T cells simulating panniculitis and preferentially infiltrating the subcutaneous tissue.¹ Subcutaneous panniculitislike T-cell lymphoma can affect all ages but predominantly affects younger individuals, with 20% being younger than 20 years.² It is a rare lymphoma that accounts for less than 1% of all non-Hodgkin lymphomas.³ It presents clinically as multiple subcutaneous masses, nodules, or plaques generally on the trunk or extremities.^1,2 The skin surrounding the nodules may be erythematous, and the nodules may become necrotic; however, ulceration typically is not seen. Systemic symptoms such as fever, night sweats, and chills are present in half of cases.¹ According to the World Health Organization, cytopenia and elevated liver function tests are common, and a hemophagocytic syndrome may be present in 15% to 20% of cases.³ The presence of a hemophagocytic syndrome yields a poor prognosis.^1,3 Current guidelines denote that SPTCL T-cell receptor (TCR) αβ; is a distinct entity from the TCRγδ; phenotype, known as cutaneous γδ-positive T-cell lymphoma.^3,4 Cutaneous γδ-positive T-cell lymphoma is associated with rapid decline and a worse prognosis.⁴  

Histology of SPTCL is characteristic for a lobular panniculitislike infiltrate.¹ The heavy subcutaneous lymphoid infiltrate is composed of atypical small- to medium-sized lymphocytes with mature chromatin and inconspicuous nucleoli lining adipocytes. The dense inflammatory infiltrate composed predominantly of neoplastic T cells and macrophages may diffusely invade into the subcutaneous tissue.¹ Admixed histocytes and karyorrhectic debris as well as rimming of the lymphocytes around the fat cells is typical and was seen in our patient (quiz image). The T cells of SPTCL have the following immunophenotype: TCR-beta F1⁺, CD3⁺, CD4^-, CD8⁺, CD56^-. They can express numerous cytotoxic proteins, such as T1a-1, granzyme B, and perforin.^2,3 Although the CD8⁺ T cells may be sparse, they generally surround the adipocytes in a rimming manner and may distort the adipocyte membrane.¹  

Lupus erythematosus profundus (LEP) is a form of chronic cutaneous lupus that affects the deep dermis and fat.⁵ It also can present clinically as tender plaques or nodules. It most frequently involves the upper arms, shoulders, face, or buttocks--areas that are less commonly involved in other panniculitides.⁶ Histologically, LEP is similar to chronic discoid lupus with features such as epidermal atrophy, interface changes, and a thickened basement membrane (Figure 1). Lupus erythematosus profundus can present as a lobular panniculitis with mucin as well as a superficial and deep lymphocytic infiltrate that can involve the septa.⁵ Some cases of LEP have a predominantly lobular lymphocytic panniculitis in the absence of the typical epidermal or dermal changes of lupus erythematosus. Lymphoid follicles with germinal center formation are present in half of cases and reportedly are characteristic of LEP.^6,7 The lymphoid follicles often have plasma cells, can extend into the septa as well as in between collagen bundles, and may have nuclear fragmentation.⁵ Another characteristic feature of LEP is hyaline sclerosis of lobules with focal extension into the interlobular septa. Immunofluorescence studies usually show linear deposition of IgM and C3 at the dermoepidermal junction. Antinuclear antibodies can be present in patients who have LEP but are not entirely specific.⁶  

Lupus erythematosus profundus and SPTCL are part of a spectrum and may have overlapping clinical and histopathologic characteristics; therefore, distinguishing them may be difficult.^6-8 It is important to monitor these patients closely, as their disease may progress to lymphoma.⁶ Patients with SPTCL are more likely to present with advanced symptoms such as fever and hepatosplenomegaly and to succumb to hemophagocytic syndrome than patients with LEP.⁹  

Although SPTCL usually is clonal, several cases of LEP with clonality also have been described. Clonal LEP cases generally are identified in patients who present with fever and cytopenia.⁸ Lymphoid atypia and morphologic abnormalities may be seen in cases of LEP, further complicating the distinction between LEP and SPTCL. An elevated Ki67 level may be seen in cases of SPTCL with periadipocytic rimming.⁹ LeBlanc et al¹⁰ used Ki67 "hot spots" along with CD8 immunohistochemistry to identify atypical lymphocytes associated with SPTCL. Lymphocyte rimming was defined by the presence of CD8⁺ lymphocytes with an elevated Ki67 index. Clinical, histopathologic, and molecular findings all should be used when dealing with challenging cases.  

Fat necrosis can occur in any part of the body where trauma has occurred and can be associated with many disease processes. Patients typically present with a palpable mass, but a clinical history of trauma is not always present. Histopathologic findings include necrotic fat alongside lipid-laden foamy macrophages and scattered inflammatory cells (Figure 2).¹¹ Fragments of normal as well as degenerating adipose tissue and multinucleated giant cells can be present.  

Erythema nodosum (EN) is the most frequently encountered panniculitis and usually is seen in women in early adulthood.¹² Patients present with several tender subcutaneous nodules and plaques that most commonly are present on the anterior surface of the legs.^12,13 Patients may have a constellation of symptoms including fever and leukocytosis, but the disorder generally is self-limited.¹² Erythema nodosum may be associated with a variety of diseases or infections including sarcoidosis, inflammatory bowel disease, and malignancy.¹⁴ The etiology of EN is diverse; therefore, a proper clinical workup may be necessary. Histopathology is that of a septal panniculitis with lymphocytes, histiocytes, and occasional eosinophils (Figure 3).¹³  

Lipodermatosclerosis also occurs on the legs, most commonly in patients with venous insufficiency.^12,15 Patients present clinically with pain, induration, redness, or swelling of the legs. Histopathology predominantly is characterized by membranous fat necrosis, fibrosis, and fatty microcysts that may be lined by a thickened hyaline membrane (Figure 4). Lipodermatosclerosis lesions generally do not resolve spontaneously and may need to be treated.¹⁶ 

The Diagnosis: Subcutaneous Panniculitislike T-cell Lymphoma 

Subcutaneous panniculitislike T-cell lymphoma (SPTCL) is a rare form of cutaneous lymphoma of mature cytotoxic T cells simulating panniculitis and preferentially infiltrating the subcutaneous tissue.¹ Subcutaneous panniculitislike T-cell lymphoma can affect all ages but predominantly affects younger individuals, with 20% being younger than 20 years.² It is a rare lymphoma that accounts for less than 1% of all non-Hodgkin lymphomas.³ It presents clinically as multiple subcutaneous masses, nodules, or plaques generally on the trunk or extremities.^1,2 The skin surrounding the nodules may be erythematous, and the nodules may become necrotic; however, ulceration typically is not seen. Systemic symptoms such as fever, night sweats, and chills are present in half of cases.¹ According to the World Health Organization, cytopenia and elevated liver function tests are common, and a hemophagocytic syndrome may be present in 15% to 20% of cases.³ The presence of a hemophagocytic syndrome yields a poor prognosis.^1,3 Current guidelines denote that SPTCL T-cell receptor (TCR) αβ; is a distinct entity from the TCRγδ; phenotype, known as cutaneous γδ-positive T-cell lymphoma.^3,4 Cutaneous γδ-positive T-cell lymphoma is associated with rapid decline and a worse prognosis.⁴  

Histology of SPTCL is characteristic for a lobular panniculitislike infiltrate.¹ The heavy subcutaneous lymphoid infiltrate is composed of atypical small- to medium-sized lymphocytes with mature chromatin and inconspicuous nucleoli lining adipocytes. The dense inflammatory infiltrate composed predominantly of neoplastic T cells and macrophages may diffusely invade into the subcutaneous tissue.¹ Admixed histocytes and karyorrhectic debris as well as rimming of the lymphocytes around the fat cells is typical and was seen in our patient (quiz image). The T cells of SPTCL have the following immunophenotype: TCR-beta F1⁺, CD3⁺, CD4^-, CD8⁺, CD56^-. They can express numerous cytotoxic proteins, such as T1a-1, granzyme B, and perforin.^2,3 Although the CD8⁺ T cells may be sparse, they generally surround the adipocytes in a rimming manner and may distort the adipocyte membrane.¹  

Lupus erythematosus profundus (LEP) is a form of chronic cutaneous lupus that affects the deep dermis and fat.⁵ It also can present clinically as tender plaques or nodules. It most frequently involves the upper arms, shoulders, face, or buttocks--areas that are less commonly involved in other panniculitides.⁶ Histologically, LEP is similar to chronic discoid lupus with features such as epidermal atrophy, interface changes, and a thickened basement membrane (Figure 1). Lupus erythematosus profundus can present as a lobular panniculitis with mucin as well as a superficial and deep lymphocytic infiltrate that can involve the septa.⁵ Some cases of LEP have a predominantly lobular lymphocytic panniculitis in the absence of the typical epidermal or dermal changes of lupus erythematosus. Lymphoid follicles with germinal center formation are present in half of cases and reportedly are characteristic of LEP.^6,7 The lymphoid follicles often have plasma cells, can extend into the septa as well as in between collagen bundles, and may have nuclear fragmentation.⁵ Another characteristic feature of LEP is hyaline sclerosis of lobules with focal extension into the interlobular septa. Immunofluorescence studies usually show linear deposition of IgM and C3 at the dermoepidermal junction. Antinuclear antibodies can be present in patients who have LEP but are not entirely specific.⁶  

Lupus erythematosus profundus and SPTCL are part of a spectrum and may have overlapping clinical and histopathologic characteristics; therefore, distinguishing them may be difficult.^6-8 It is important to monitor these patients closely, as their disease may progress to lymphoma.⁶ Patients with SPTCL are more likely to present with advanced symptoms such as fever and hepatosplenomegaly and to succumb to hemophagocytic syndrome than patients with LEP.⁹  

Although SPTCL usually is clonal, several cases of LEP with clonality also have been described. Clonal LEP cases generally are identified in patients who present with fever and cytopenia.⁸ Lymphoid atypia and morphologic abnormalities may be seen in cases of LEP, further complicating the distinction between LEP and SPTCL. An elevated Ki67 level may be seen in cases of SPTCL with periadipocytic rimming.⁹ LeBlanc et al¹⁰ used Ki67 "hot spots" along with CD8 immunohistochemistry to identify atypical lymphocytes associated with SPTCL. Lymphocyte rimming was defined by the presence of CD8⁺ lymphocytes with an elevated Ki67 index. Clinical, histopathologic, and molecular findings all should be used when dealing with challenging cases.  

Fat necrosis can occur in any part of the body where trauma has occurred and can be associated with many disease processes. Patients typically present with a palpable mass, but a clinical history of trauma is not always present. Histopathologic findings include necrotic fat alongside lipid-laden foamy macrophages and scattered inflammatory cells (Figure 2).¹¹ Fragments of normal as well as degenerating adipose tissue and multinucleated giant cells can be present.  

Erythema nodosum (EN) is the most frequently encountered panniculitis and usually is seen in women in early adulthood.¹² Patients present with several tender subcutaneous nodules and plaques that most commonly are present on the anterior surface of the legs.^12,13 Patients may have a constellation of symptoms including fever and leukocytosis, but the disorder generally is self-limited.¹² Erythema nodosum may be associated with a variety of diseases or infections including sarcoidosis, inflammatory bowel disease, and malignancy.¹⁴ The etiology of EN is diverse; therefore, a proper clinical workup may be necessary. Histopathology is that of a septal panniculitis with lymphocytes, histiocytes, and occasional eosinophils (Figure 3).¹³  

Lipodermatosclerosis also occurs on the legs, most commonly in patients with venous insufficiency.^12,15 Patients present clinically with pain, induration, redness, or swelling of the legs. Histopathology predominantly is characterized by membranous fat necrosis, fibrosis, and fatty microcysts that may be lined by a thickened hyaline membrane (Figure 4). Lipodermatosclerosis lesions generally do not resolve spontaneously and may need to be treated.¹⁶ 

The Diagnosis: Cutaneous B-cell Lymphoma  

Histopathology was suggestive of cutaneous B-cell lymphoma (Figure). Further immunohistochemical studies including Bcl-6 positivity and Bcl-2 negativity in the large atypical cells supported a diagnosis of primary cutaneous follicle center lymphoma (PCFCL). The designation of primary cutaneous B-cell lymphoma includes several different types of lymphoma, including marginal zone lymphoma, diffuse large B-cell lymphoma, and intravascular lymphoma. To be considered a primary cutaneous lymphoma, there must be evidence of the lymphoma in the skin without concomitant evidence of systemic involvement, as determined through a full staging workup. Primary cutaneous follicle center lymphoma is an indolent lymphoma that most commonly presents as solitary or grouped, pink to plum-colored papules, plaques, nodules, and tumors on the scalp, forehead, or back.¹ The lesions often are biopsied as suspected basal cell carcinomas or Merkel cell carcinomas (MCCs). Lesions on the face or scalp may easily evade diagnosis, as they initially may mimic rosacea or insect bites. Less common presentations include infiltrative lesions that cause rhinophymatous changes or scarring alopecia. Multifocal or disseminated lesions rarely can be observed. This case presentation is unique in its patchy appearance that clinically resembled angiosarcoma.² When identified and treated, the disease-specific 5-year survival rate for PCFCL is greater than 95%.³  

Merkel cell carcinoma was first described in 1972 and has been diagnosed with increasing frequency each year.⁴ It generally presents as an erythematous or violaceous, tender, indurated nodule on sun-exposed skin of the head or neck in elderly White men. However, other presentations have been reported, including papules, plaques, cystlike structures, pruritic tumors, pedunculated lesions, subcutaneous masses, and telangiectatic papules.⁵ Histopathologically, MCC is characterized by dermal nests and sheets of basaloid cells with finely granular salt and pepper-like chromatin. The histologic features can resemble other small blue cell tumors; therefore, the differential diagnosis can be broad.⁵ Immunohistochemistry that can confirm the diagnosis of MCC generally will be positive for cytokeratin 20 and neuroendocrine markers but negative for cytokeratin ⁷ and thyroid transcription factor ¹. Merkel cell carcinoma is an aggressive tumor with a high risk for local recurrence and distant metastasis that carries a generally poor prognosis, especially when there is evidence of metastatic disease at presentation.^5,6  

Rosacea can appear as telangiectatic patches, though generally not as one discrete patch limited to the forehead, as in our patient. Histologic features vary based on the age of the lesion and clinical variant. In early lesions there is a mild perivascular lymphoplasmacytic infiltrate within the dermis, while older lesions can have a mixed infiltrate crowded around vessels and adnexal structures. Granulomas often are seen near hair follicles and interspersed throughout the dermis with ectatic vessels and dermal edema.⁷  

Angiosarcoma is divided into 3 clinicopathological subtypes: idiopathic angiosarcoma of the head and neck, angiosarcoma in the setting of lymphedema, and postirradiation angiosarcoma.⁷ Idiopathic angiosarcoma most closely mimics PCFCL, as it can present as single or multifocal nodules, plaques, or patches. Histologically, the 3 groups appear similar with poorly circumscribed, infiltrative, dermal tumors. The neoplastic endothelial cells have large hyperchromatic nuclei that protrude into vascular lumens. The prognosis for idiopathic angiosarcoma of the head and neck is poor, with a 5-year survival rate of 15% to 34%, which often is due to delayed diagnosis.⁷ 

Pigmented purpuric dermatoses (PPDs) are chronic skin disorders characterized by purpura due to extravasation of blood from capillaries; the resulting hemosiderin deposition leads to pigmentation.⁷ There are various forms of PPD, which are classified into groups based on clinical appearance including Schamberg disease, purpura annularis telangiectodes of Majocchi, pigmented purpuric lichenoid dermatosis of Gougerot and Blum, lichen aureus, and others including eczematid and itching variants, which some consider to be distinct entities. Purpura annularis telangiectodes of Majocchi is the specific PPD that should be included in the clinical differential for PCFCL because it presents as annular patches with telangiectasias. Histologically, PPDs are characterized by a CD4⁺ lymphocytic infiltrate in the upper dermis with extravasated red blood cells and the presence of hemosiderin mostly within macrophages and a lack of true vasculitis. Clonality of the T cells has been shown, and there is some evidence that PPD may overlap with mycosis fungoides. However, this overlap mainly has been seen in patients with widespread lesions and would not apply to this case. In general, patients with PPD can be reassured of the benign process. In cases of widespread PPD, patients should be followed clinically to assess for progression to mycosis fungoides, though the likelihood is low.⁷  

Our patient underwent a full staging workup, which confirmed the diagnosis of PCFCL. He was treated with radiation to the forehead that resulted in clearance of the lesion. Approximately 2 years after the initial diagnosis, the patient was alive and well with no evidence of recurrence of PCFCL. 

In conclusion, it is imperative to identify unusual, macular, vascular-appearing patches, especially on the head and neck in older individuals. Because the clinical presentations of PCFCL, angiosarcoma, rosacea, MCC, and PPD can overlap with one another as well as with other entities, it is necessary to have a high level of suspicion and low threshold to biopsy these types of lesions, as outcomes can be drastically different. 

The Diagnosis: Cutaneous B-cell Lymphoma  

Histopathology was suggestive of cutaneous B-cell lymphoma (Figure). Further immunohistochemical studies including Bcl-6 positivity and Bcl-2 negativity in the large atypical cells supported a diagnosis of primary cutaneous follicle center lymphoma (PCFCL). The designation of primary cutaneous B-cell lymphoma includes several different types of lymphoma, including marginal zone lymphoma, diffuse large B-cell lymphoma, and intravascular lymphoma. To be considered a primary cutaneous lymphoma, there must be evidence of the lymphoma in the skin without concomitant evidence of systemic involvement, as determined through a full staging workup. Primary cutaneous follicle center lymphoma is an indolent lymphoma that most commonly presents as solitary or grouped, pink to plum-colored papules, plaques, nodules, and tumors on the scalp, forehead, or back.¹ The lesions often are biopsied as suspected basal cell carcinomas or Merkel cell carcinomas (MCCs). Lesions on the face or scalp may easily evade diagnosis, as they initially may mimic rosacea or insect bites. Less common presentations include infiltrative lesions that cause rhinophymatous changes or scarring alopecia. Multifocal or disseminated lesions rarely can be observed. This case presentation is unique in its patchy appearance that clinically resembled angiosarcoma.² When identified and treated, the disease-specific 5-year survival rate for PCFCL is greater than 95%.³  

Merkel cell carcinoma was first described in 1972 and has been diagnosed with increasing frequency each year.⁴ It generally presents as an erythematous or violaceous, tender, indurated nodule on sun-exposed skin of the head or neck in elderly White men. However, other presentations have been reported, including papules, plaques, cystlike structures, pruritic tumors, pedunculated lesions, subcutaneous masses, and telangiectatic papules.⁵ Histopathologically, MCC is characterized by dermal nests and sheets of basaloid cells with finely granular salt and pepper-like chromatin. The histologic features can resemble other small blue cell tumors; therefore, the differential diagnosis can be broad.⁵ Immunohistochemistry that can confirm the diagnosis of MCC generally will be positive for cytokeratin 20 and neuroendocrine markers but negative for cytokeratin ⁷ and thyroid transcription factor ¹. Merkel cell carcinoma is an aggressive tumor with a high risk for local recurrence and distant metastasis that carries a generally poor prognosis, especially when there is evidence of metastatic disease at presentation.^5,6  

Rosacea can appear as telangiectatic patches, though generally not as one discrete patch limited to the forehead, as in our patient. Histologic features vary based on the age of the lesion and clinical variant. In early lesions there is a mild perivascular lymphoplasmacytic infiltrate within the dermis, while older lesions can have a mixed infiltrate crowded around vessels and adnexal structures. Granulomas often are seen near hair follicles and interspersed throughout the dermis with ectatic vessels and dermal edema.⁷  

Angiosarcoma is divided into 3 clinicopathological subtypes: idiopathic angiosarcoma of the head and neck, angiosarcoma in the setting of lymphedema, and postirradiation angiosarcoma.⁷ Idiopathic angiosarcoma most closely mimics PCFCL, as it can present as single or multifocal nodules, plaques, or patches. Histologically, the 3 groups appear similar with poorly circumscribed, infiltrative, dermal tumors. The neoplastic endothelial cells have large hyperchromatic nuclei that protrude into vascular lumens. The prognosis for idiopathic angiosarcoma of the head and neck is poor, with a 5-year survival rate of 15% to 34%, which often is due to delayed diagnosis.⁷ 

Pigmented purpuric dermatoses (PPDs) are chronic skin disorders characterized by purpura due to extravasation of blood from capillaries; the resulting hemosiderin deposition leads to pigmentation.⁷ There are various forms of PPD, which are classified into groups based on clinical appearance including Schamberg disease, purpura annularis telangiectodes of Majocchi, pigmented purpuric lichenoid dermatosis of Gougerot and Blum, lichen aureus, and others including eczematid and itching variants, which some consider to be distinct entities. Purpura annularis telangiectodes of Majocchi is the specific PPD that should be included in the clinical differential for PCFCL because it presents as annular patches with telangiectasias. Histologically, PPDs are characterized by a CD4⁺ lymphocytic infiltrate in the upper dermis with extravasated red blood cells and the presence of hemosiderin mostly within macrophages and a lack of true vasculitis. Clonality of the T cells has been shown, and there is some evidence that PPD may overlap with mycosis fungoides. However, this overlap mainly has been seen in patients with widespread lesions and would not apply to this case. In general, patients with PPD can be reassured of the benign process. In cases of widespread PPD, patients should be followed clinically to assess for progression to mycosis fungoides, though the likelihood is low.⁷  

Our patient underwent a full staging workup, which confirmed the diagnosis of PCFCL. He was treated with radiation to the forehead that resulted in clearance of the lesion. Approximately 2 years after the initial diagnosis, the patient was alive and well with no evidence of recurrence of PCFCL. 

In conclusion, it is imperative to identify unusual, macular, vascular-appearing patches, especially on the head and neck in older individuals. Because the clinical presentations of PCFCL, angiosarcoma, rosacea, MCC, and PPD can overlap with one another as well as with other entities, it is necessary to have a high level of suspicion and low threshold to biopsy these types of lesions, as outcomes can be drastically different. 

The Diagnosis: Cutaneous B-cell Lymphoma  

Histopathology was suggestive of cutaneous B-cell lymphoma (Figure). Further immunohistochemical studies including Bcl-6 positivity and Bcl-2 negativity in the large atypical cells supported a diagnosis of primary cutaneous follicle center lymphoma (PCFCL). The designation of primary cutaneous B-cell lymphoma includes several different types of lymphoma, including marginal zone lymphoma, diffuse large B-cell lymphoma, and intravascular lymphoma. To be considered a primary cutaneous lymphoma, there must be evidence of the lymphoma in the skin without concomitant evidence of systemic involvement, as determined through a full staging workup. Primary cutaneous follicle center lymphoma is an indolent lymphoma that most commonly presents as solitary or grouped, pink to plum-colored papules, plaques, nodules, and tumors on the scalp, forehead, or back.¹ The lesions often are biopsied as suspected basal cell carcinomas or Merkel cell carcinomas (MCCs). Lesions on the face or scalp may easily evade diagnosis, as they initially may mimic rosacea or insect bites. Less common presentations include infiltrative lesions that cause rhinophymatous changes or scarring alopecia. Multifocal or disseminated lesions rarely can be observed. This case presentation is unique in its patchy appearance that clinically resembled angiosarcoma.² When identified and treated, the disease-specific 5-year survival rate for PCFCL is greater than 95%.³  

Merkel cell carcinoma was first described in 1972 and has been diagnosed with increasing frequency each year.⁴ It generally presents as an erythematous or violaceous, tender, indurated nodule on sun-exposed skin of the head or neck in elderly White men. However, other presentations have been reported, including papules, plaques, cystlike structures, pruritic tumors, pedunculated lesions, subcutaneous masses, and telangiectatic papules.⁵ Histopathologically, MCC is characterized by dermal nests and sheets of basaloid cells with finely granular salt and pepper-like chromatin. The histologic features can resemble other small blue cell tumors; therefore, the differential diagnosis can be broad.⁵ Immunohistochemistry that can confirm the diagnosis of MCC generally will be positive for cytokeratin 20 and neuroendocrine markers but negative for cytokeratin ⁷ and thyroid transcription factor ¹. Merkel cell carcinoma is an aggressive tumor with a high risk for local recurrence and distant metastasis that carries a generally poor prognosis, especially when there is evidence of metastatic disease at presentation.^5,6  

Rosacea can appear as telangiectatic patches, though generally not as one discrete patch limited to the forehead, as in our patient. Histologic features vary based on the age of the lesion and clinical variant. In early lesions there is a mild perivascular lymphoplasmacytic infiltrate within the dermis, while older lesions can have a mixed infiltrate crowded around vessels and adnexal structures. Granulomas often are seen near hair follicles and interspersed throughout the dermis with ectatic vessels and dermal edema.⁷  

Angiosarcoma is divided into 3 clinicopathological subtypes: idiopathic angiosarcoma of the head and neck, angiosarcoma in the setting of lymphedema, and postirradiation angiosarcoma.⁷ Idiopathic angiosarcoma most closely mimics PCFCL, as it can present as single or multifocal nodules, plaques, or patches. Histologically, the 3 groups appear similar with poorly circumscribed, infiltrative, dermal tumors. The neoplastic endothelial cells have large hyperchromatic nuclei that protrude into vascular lumens. The prognosis for idiopathic angiosarcoma of the head and neck is poor, with a 5-year survival rate of 15% to 34%, which often is due to delayed diagnosis.⁷ 

Pigmented purpuric dermatoses (PPDs) are chronic skin disorders characterized by purpura due to extravasation of blood from capillaries; the resulting hemosiderin deposition leads to pigmentation.⁷ There are various forms of PPD, which are classified into groups based on clinical appearance including Schamberg disease, purpura annularis telangiectodes of Majocchi, pigmented purpuric lichenoid dermatosis of Gougerot and Blum, lichen aureus, and others including eczematid and itching variants, which some consider to be distinct entities. Purpura annularis telangiectodes of Majocchi is the specific PPD that should be included in the clinical differential for PCFCL because it presents as annular patches with telangiectasias. Histologically, PPDs are characterized by a CD4⁺ lymphocytic infiltrate in the upper dermis with extravasated red blood cells and the presence of hemosiderin mostly within macrophages and a lack of true vasculitis. Clonality of the T cells has been shown, and there is some evidence that PPD may overlap with mycosis fungoides. However, this overlap mainly has been seen in patients with widespread lesions and would not apply to this case. In general, patients with PPD can be reassured of the benign process. In cases of widespread PPD, patients should be followed clinically to assess for progression to mycosis fungoides, though the likelihood is low.⁷  

Our patient underwent a full staging workup, which confirmed the diagnosis of PCFCL. He was treated with radiation to the forehead that resulted in clearance of the lesion. Approximately 2 years after the initial diagnosis, the patient was alive and well with no evidence of recurrence of PCFCL. 

In conclusion, it is imperative to identify unusual, macular, vascular-appearing patches, especially on the head and neck in older individuals. Because the clinical presentations of PCFCL, angiosarcoma, rosacea, MCC, and PPD can overlap with one another as well as with other entities, it is necessary to have a high level of suspicion and low threshold to biopsy these types of lesions, as outcomes can be drastically different. 

The Diagnosis: Subcutaneous Granuloma Annulare 

Subcutaneous granuloma annulare (SGA), also known as deep GA, is a rare variant of GA that usually occurs in children and young adults. It presents as single or multiple, nontender, deep dermal and/or subcutaneous nodules with normal-appearing skin usually on the anterior lower legs, dorsal aspects of the hands and fingers, scalp, or buttocks.^1-3 The pathogenesis of SGA as well as GA is not fully understood, and proposed inciting factors include trauma, insect bite reactions, tuberculin skin testing, vaccines, UV exposure, medications, and viral infections.^3-6 A cell-mediated, delayed-type hypersensitivity reaction to an unknown antigen also has been postulated as a possible mechanism.⁷ Treatment usually is not necessary, as the nature of the condition is benign and the course often is self-limited. Spontaneous resolution occurs within 2 years in 50% of patients with localized GA.^4,8 Surgery usually is not recommended due to the high recurrence rate (40%-75%).^4,9  

Absence of epidermal change in this entity obfuscates clinical recognition, and accurate diagnosis often depends on punch or excisional biopsies revealing characteristic histopathology. The histology of SGA consists of palisaded granulomas with central areas of necrobiosis composed of degenerated collagen, mucin deposition, and nuclear dust from neutrophils that extend into the deep dermis and subcutis.² The periphery of the granulomas is lined by palisading epithelioid histiocytes with occasional multinucleated giant cells.^10,11 Eosinophils often are present.¹² Colloidal iron and Alcian blue stains can be used to highlight the abundant connective tissue mucin of the granulomas.⁴  

The histologic differential diagnosis of SGA includes rheumatoid nodule, necrobiosis lipoidica, epithelioid sarcoma, and tophaceous gout.² Rheumatoid nodules are the most common dermatologic presentation of rheumatoid arthritis and are found in up to 30% to 40% of patients with the disease.^13-15 They present as firm, painless, subcutaneous papulonodules on the extensor surfaces and at sites of trauma or pressure. Histologically, rheumatoid nodules exhibit a homogenous and eosinophilic central area of necrobiosis with fibrin deposition and absent mucin deep within the dermis and subcutaneous tissue (Figure 1). In contrast, granulomas in SGA usually are pale and basophilic with abundant mucin.²  

Necrobiosis lipoidica is a rare chronic granulomatous disease of the skin that most commonly occurs in young to middle-aged adults and is strongly associated with diabetes mellitus.¹⁶ It clinically presents as yellow to red-brown papules and plaques with a peripheral erythematous to violaceous rim usually on the pretibial area. Over time, lesions become yellowish atrophic patches and plaques that sometimes can ulcerate. Histopathology reveals areas of horizontally arranged, palisaded, and interstitial granulomatous dermatitis intermixed with areas of degenerated collagen and widespread fibrosis extending from the superficial dermis into the subcutis (Figure 2).² These areas lack mucin and have an increased number of plasma cells. Eosinophils and/or lymphoid nodules occasionally can be seen.^17,18 

Epithelioid sarcoma is a rare malignant soft tissue sarcoma that tends to occur on the distal extremities in younger patients, typically aged 20 to 40 years, often with preceding trauma to the area. It usually presents as a solitary, poorly defined, hard, subcutaneous nodule. Histologic analysis shows central areas of necrosis and degenerated collagen surrounded by epithelioid and spindle cells with hyperchromatic and pleomorphic nuclei and mitoses (Figure 3).² These tumor cells express positivity for keratins, vimentin, epithelial membrane antigen, and CD34, while they usually are negative for desmin, S-100, and FLI-1 nuclear transcription factor.^2,4,19  

Tophaceous gout results from the accumulation of monosodium urate crystals in the skin. It clinically presents as firm, white-yellow, dermal and subcutaneous papulonodules on the helix of the ear and the skin overlying joints. Histopathology reveals palisaded granulomas surrounding an amorphous feathery material that corresponds to the urate crystals that were destroyed with formalin fixation (Figure 4). When the tissue is fixed with ethanol or is incompletely fixed in formalin, birefringent urate crystals are evident with polarization.²⁰

The Diagnosis: Subcutaneous Granuloma Annulare 

Subcutaneous granuloma annulare (SGA), also known as deep GA, is a rare variant of GA that usually occurs in children and young adults. It presents as single or multiple, nontender, deep dermal and/or subcutaneous nodules with normal-appearing skin usually on the anterior lower legs, dorsal aspects of the hands and fingers, scalp, or buttocks.^1-3 The pathogenesis of SGA as well as GA is not fully understood, and proposed inciting factors include trauma, insect bite reactions, tuberculin skin testing, vaccines, UV exposure, medications, and viral infections.^3-6 A cell-mediated, delayed-type hypersensitivity reaction to an unknown antigen also has been postulated as a possible mechanism.⁷ Treatment usually is not necessary, as the nature of the condition is benign and the course often is self-limited. Spontaneous resolution occurs within 2 years in 50% of patients with localized GA.^4,8 Surgery usually is not recommended due to the high recurrence rate (40%-75%).^4,9  

Absence of epidermal change in this entity obfuscates clinical recognition, and accurate diagnosis often depends on punch or excisional biopsies revealing characteristic histopathology. The histology of SGA consists of palisaded granulomas with central areas of necrobiosis composed of degenerated collagen, mucin deposition, and nuclear dust from neutrophils that extend into the deep dermis and subcutis.² The periphery of the granulomas is lined by palisading epithelioid histiocytes with occasional multinucleated giant cells.^10,11 Eosinophils often are present.¹² Colloidal iron and Alcian blue stains can be used to highlight the abundant connective tissue mucin of the granulomas.⁴  

The histologic differential diagnosis of SGA includes rheumatoid nodule, necrobiosis lipoidica, epithelioid sarcoma, and tophaceous gout.² Rheumatoid nodules are the most common dermatologic presentation of rheumatoid arthritis and are found in up to 30% to 40% of patients with the disease.^13-15 They present as firm, painless, subcutaneous papulonodules on the extensor surfaces and at sites of trauma or pressure. Histologically, rheumatoid nodules exhibit a homogenous and eosinophilic central area of necrobiosis with fibrin deposition and absent mucin deep within the dermis and subcutaneous tissue (Figure 1). In contrast, granulomas in SGA usually are pale and basophilic with abundant mucin.²  

Necrobiosis lipoidica is a rare chronic granulomatous disease of the skin that most commonly occurs in young to middle-aged adults and is strongly associated with diabetes mellitus.¹⁶ It clinically presents as yellow to red-brown papules and plaques with a peripheral erythematous to violaceous rim usually on the pretibial area. Over time, lesions become yellowish atrophic patches and plaques that sometimes can ulcerate. Histopathology reveals areas of horizontally arranged, palisaded, and interstitial granulomatous dermatitis intermixed with areas of degenerated collagen and widespread fibrosis extending from the superficial dermis into the subcutis (Figure 2).² These areas lack mucin and have an increased number of plasma cells. Eosinophils and/or lymphoid nodules occasionally can be seen.^17,18 

Epithelioid sarcoma is a rare malignant soft tissue sarcoma that tends to occur on the distal extremities in younger patients, typically aged 20 to 40 years, often with preceding trauma to the area. It usually presents as a solitary, poorly defined, hard, subcutaneous nodule. Histologic analysis shows central areas of necrosis and degenerated collagen surrounded by epithelioid and spindle cells with hyperchromatic and pleomorphic nuclei and mitoses (Figure 3).² These tumor cells express positivity for keratins, vimentin, epithelial membrane antigen, and CD34, while they usually are negative for desmin, S-100, and FLI-1 nuclear transcription factor.^2,4,19  

Tophaceous gout results from the accumulation of monosodium urate crystals in the skin. It clinically presents as firm, white-yellow, dermal and subcutaneous papulonodules on the helix of the ear and the skin overlying joints. Histopathology reveals palisaded granulomas surrounding an amorphous feathery material that corresponds to the urate crystals that were destroyed with formalin fixation (Figure 4). When the tissue is fixed with ethanol or is incompletely fixed in formalin, birefringent urate crystals are evident with polarization.²⁰

The Diagnosis: Subcutaneous Granuloma Annulare 

Subcutaneous granuloma annulare (SGA), also known as deep GA, is a rare variant of GA that usually occurs in children and young adults. It presents as single or multiple, nontender, deep dermal and/or subcutaneous nodules with normal-appearing skin usually on the anterior lower legs, dorsal aspects of the hands and fingers, scalp, or buttocks.^1-3 The pathogenesis of SGA as well as GA is not fully understood, and proposed inciting factors include trauma, insect bite reactions, tuberculin skin testing, vaccines, UV exposure, medications, and viral infections.^3-6 A cell-mediated, delayed-type hypersensitivity reaction to an unknown antigen also has been postulated as a possible mechanism.⁷ Treatment usually is not necessary, as the nature of the condition is benign and the course often is self-limited. Spontaneous resolution occurs within 2 years in 50% of patients with localized GA.^4,8 Surgery usually is not recommended due to the high recurrence rate (40%-75%).^4,9  

Absence of epidermal change in this entity obfuscates clinical recognition, and accurate diagnosis often depends on punch or excisional biopsies revealing characteristic histopathology. The histology of SGA consists of palisaded granulomas with central areas of necrobiosis composed of degenerated collagen, mucin deposition, and nuclear dust from neutrophils that extend into the deep dermis and subcutis.² The periphery of the granulomas is lined by palisading epithelioid histiocytes with occasional multinucleated giant cells.^10,11 Eosinophils often are present.¹² Colloidal iron and Alcian blue stains can be used to highlight the abundant connective tissue mucin of the granulomas.⁴  

The histologic differential diagnosis of SGA includes rheumatoid nodule, necrobiosis lipoidica, epithelioid sarcoma, and tophaceous gout.² Rheumatoid nodules are the most common dermatologic presentation of rheumatoid arthritis and are found in up to 30% to 40% of patients with the disease.^13-15 They present as firm, painless, subcutaneous papulonodules on the extensor surfaces and at sites of trauma or pressure. Histologically, rheumatoid nodules exhibit a homogenous and eosinophilic central area of necrobiosis with fibrin deposition and absent mucin deep within the dermis and subcutaneous tissue (Figure 1). In contrast, granulomas in SGA usually are pale and basophilic with abundant mucin.²  

Necrobiosis lipoidica is a rare chronic granulomatous disease of the skin that most commonly occurs in young to middle-aged adults and is strongly associated with diabetes mellitus.¹⁶ It clinically presents as yellow to red-brown papules and plaques with a peripheral erythematous to violaceous rim usually on the pretibial area. Over time, lesions become yellowish atrophic patches and plaques that sometimes can ulcerate. Histopathology reveals areas of horizontally arranged, palisaded, and interstitial granulomatous dermatitis intermixed with areas of degenerated collagen and widespread fibrosis extending from the superficial dermis into the subcutis (Figure 2).² These areas lack mucin and have an increased number of plasma cells. Eosinophils and/or lymphoid nodules occasionally can be seen.^17,18 

Epithelioid sarcoma is a rare malignant soft tissue sarcoma that tends to occur on the distal extremities in younger patients, typically aged 20 to 40 years, often with preceding trauma to the area. It usually presents as a solitary, poorly defined, hard, subcutaneous nodule. Histologic analysis shows central areas of necrosis and degenerated collagen surrounded by epithelioid and spindle cells with hyperchromatic and pleomorphic nuclei and mitoses (Figure 3).² These tumor cells express positivity for keratins, vimentin, epithelial membrane antigen, and CD34, while they usually are negative for desmin, S-100, and FLI-1 nuclear transcription factor.^2,4,19  

Tophaceous gout results from the accumulation of monosodium urate crystals in the skin. It clinically presents as firm, white-yellow, dermal and subcutaneous papulonodules on the helix of the ear and the skin overlying joints. Histopathology reveals palisaded granulomas surrounding an amorphous feathery material that corresponds to the urate crystals that were destroyed with formalin fixation (Figure 4). When the tissue is fixed with ethanol or is incompletely fixed in formalin, birefringent urate crystals are evident with polarization.²⁰

Basal cell carcinoma (BCC) is the most common type of skin cancer frequently encountered in both dermatology and primary care settings.¹ When biopsies of these neoplasms are performed to confirm the diagnosis, pathology reports may indicate positive or negative margin status. No guidelines exist for reporting biopsy margin status for BCC, resulting in varied reporting practices among dermatopathologists. Furthermore, the terminology used to describe margin status can be ambiguous and differs among pathologists; language such as “approaches the margin” or “margins appear free” may be used, with nonuniform interpretation between pathologists and providers, leading to variability in patient management.²

When interpreting a negative margin status on a pathology report, one must question if the BCC extends beyond the margin in unexamined sections of the specimen, which could be the result of an irregular tumor growth pattern or tissue processing. It has been estimated that less than 2% of the peripheral surgical margin is ultimately examined when serial cross-sections are prepared histologically (the bread loaf technique). However, this estimation would depend on several variables, including the number and thickness of sections and the amount of tissue discarded during processing.³ Importantly, reports of a false-negative margin could lead both the clinician and patient to believe that the neoplasm has been completely removed, which could have serious consequences.

Our study sought to determine the reliability of negative biopsy margin status for BCC. We examined BCC biopsy specimens initially determined to have uninvolved margins on routine tissue processing and determined the proportion with truly negative margins after complete tissue block sectioning of the initial biopsy specimen. We felt this technique was a more accurate measurement of true margin status than examination of a re-excision specimen. We also identified any factors that were predictive of positive true margins.

Methods

We conducted a retrospective study evaluating tissue samples collected at Geisinger Health System (Danville, Pennsylvania) from January to December 2016. Specimens were queried via the electronic database system at our institution (CoPath). We included BCC biopsy specimens with negative histologic margins on initial assessment that subsequently had block exhaust levels routinely ordered. These levels are cut every 100 to 150 µm, generating approximately 8 glass slides. We excluded all tumors that did not fit these criteria as well as those in patients younger than 18 years. Data collection was performed utilizing specimen pathology reports in addition to the note from the corresponding clinician office visit from the institution’s electronic medical record (Epic). Appropriate statistical calculations were performed. This study was approved by an institutional review board at our institution, which is required for all research involving human participants. This served to ensure the proper review and storage of patients’ protected health information.

Results

The search yielded a total of 122 specimens from 104 patients after appropriate exclusions. We examined a total of 122 BCC biopsy specimens with negative initial margins: 121 (99.2%) shave biopsies and 1 (0.8%) punch biopsy. Of 122 specimens with negative initial margins, 53 (43.4%) were found to have a truly positive margin based on the presence of either tumor or stroma at the lateral or deep tissue edge after complete tissue block sectioning. Sixty-nine (56.6%) specimens had clear margins and were categorized as truly negative after complete tissue block sectioning. Specimens with positive and negative final margin status did not differ significantly with respect to patient age; gender; biopsy technique; number of gross specimen sections; or tumor characteristics, including location, size, and subtype (Table)(P>.05).

We also examined the type of treatment performed, which varied and included curettage, electrodesiccation and curettage, excision, and Mohs micrographic surgery. Clinicians, who were not made aware of the exhaust level protocol, chose not to pursue further treatment in 6 (4.9%) of the cases because of negative biopsy margins. Four (66.7%) of the 6 providers were physicians, and 2 (33.3%) were advanced practitioners. All of the providers practiced within the Department of Dermatology.

Comment

Our findings support prior smaller studies investigating this topic. A prospective study by Schnebelen et al⁴ examined 27 BCC biopsy specimens and found that 8 (30%) were erroneously classified as negative on routine examination. This study similarly determined true margin status by assessing the margins at complete tissue block exhaustion.⁴ Willardson et al⁵ also demonstrated the poor predictive value of margin status based on the presence of residual BCC in subsequent excisions. They found that 34 (24%) of 143 cases with negative biopsy margins contained residual tumor in the corresponding excision.⁵

Our study revealed that almost half of BCC biopsy specimens that had negative histologic margins with routine sectioning had truly positive margins on complete block exhaustion. This finding was independent of multiple factors, including tumor subtype, indicating that even nonaggressive tumors are prone to false-negative margin reports. We also found that reports of negative margins persuaded some clinicians to forgo definitive treatment. This study serves to remind clinicians of the limitations of margin assessment and provides impetus for dermatopathologists to consider modifying how margin status is reported.

Limitations of this study include a small number of cases and limited generalizability. Institutions that routinely examine more levels of each biopsy specimen may be less likely to erroneously categorize a positive margin as negative. Furthermore, despite exhausting the tissue block, we still may have underestimated the number of cases with truly positive margins, as this method inherently does not allow for complete margin examination.

Acknowledgments
We thank the Geisinger Department of Dermatopathology and the Geisinger Biostatistics & Research Data Core (Danville, Pennsylvania) for their assistance with our project.

Basal cell carcinoma (BCC) is the most common type of skin cancer frequently encountered in both dermatology and primary care settings.¹ When biopsies of these neoplasms are performed to confirm the diagnosis, pathology reports may indicate positive or negative margin status. No guidelines exist for reporting biopsy margin status for BCC, resulting in varied reporting practices among dermatopathologists. Furthermore, the terminology used to describe margin status can be ambiguous and differs among pathologists; language such as “approaches the margin” or “margins appear free” may be used, with nonuniform interpretation between pathologists and providers, leading to variability in patient management.²

When interpreting a negative margin status on a pathology report, one must question if the BCC extends beyond the margin in unexamined sections of the specimen, which could be the result of an irregular tumor growth pattern or tissue processing. It has been estimated that less than 2% of the peripheral surgical margin is ultimately examined when serial cross-sections are prepared histologically (the bread loaf technique). However, this estimation would depend on several variables, including the number and thickness of sections and the amount of tissue discarded during processing.³ Importantly, reports of a false-negative margin could lead both the clinician and patient to believe that the neoplasm has been completely removed, which could have serious consequences.

Our study sought to determine the reliability of negative biopsy margin status for BCC. We examined BCC biopsy specimens initially determined to have uninvolved margins on routine tissue processing and determined the proportion with truly negative margins after complete tissue block sectioning of the initial biopsy specimen. We felt this technique was a more accurate measurement of true margin status than examination of a re-excision specimen. We also identified any factors that were predictive of positive true margins.

Methods

We conducted a retrospective study evaluating tissue samples collected at Geisinger Health System (Danville, Pennsylvania) from January to December 2016. Specimens were queried via the electronic database system at our institution (CoPath). We included BCC biopsy specimens with negative histologic margins on initial assessment that subsequently had block exhaust levels routinely ordered. These levels are cut every 100 to 150 µm, generating approximately 8 glass slides. We excluded all tumors that did not fit these criteria as well as those in patients younger than 18 years. Data collection was performed utilizing specimen pathology reports in addition to the note from the corresponding clinician office visit from the institution’s electronic medical record (Epic). Appropriate statistical calculations were performed. This study was approved by an institutional review board at our institution, which is required for all research involving human participants. This served to ensure the proper review and storage of patients’ protected health information.

Results

The search yielded a total of 122 specimens from 104 patients after appropriate exclusions. We examined a total of 122 BCC biopsy specimens with negative initial margins: 121 (99.2%) shave biopsies and 1 (0.8%) punch biopsy. Of 122 specimens with negative initial margins, 53 (43.4%) were found to have a truly positive margin based on the presence of either tumor or stroma at the lateral or deep tissue edge after complete tissue block sectioning. Sixty-nine (56.6%) specimens had clear margins and were categorized as truly negative after complete tissue block sectioning. Specimens with positive and negative final margin status did not differ significantly with respect to patient age; gender; biopsy technique; number of gross specimen sections; or tumor characteristics, including location, size, and subtype (Table)(P>.05).

We also examined the type of treatment performed, which varied and included curettage, electrodesiccation and curettage, excision, and Mohs micrographic surgery. Clinicians, who were not made aware of the exhaust level protocol, chose not to pursue further treatment in 6 (4.9%) of the cases because of negative biopsy margins. Four (66.7%) of the 6 providers were physicians, and 2 (33.3%) were advanced practitioners. All of the providers practiced within the Department of Dermatology.

Comment

Our findings support prior smaller studies investigating this topic. A prospective study by Schnebelen et al⁴ examined 27 BCC biopsy specimens and found that 8 (30%) were erroneously classified as negative on routine examination. This study similarly determined true margin status by assessing the margins at complete tissue block exhaustion.⁴ Willardson et al⁵ also demonstrated the poor predictive value of margin status based on the presence of residual BCC in subsequent excisions. They found that 34 (24%) of 143 cases with negative biopsy margins contained residual tumor in the corresponding excision.⁵

Our study revealed that almost half of BCC biopsy specimens that had negative histologic margins with routine sectioning had truly positive margins on complete block exhaustion. This finding was independent of multiple factors, including tumor subtype, indicating that even nonaggressive tumors are prone to false-negative margin reports. We also found that reports of negative margins persuaded some clinicians to forgo definitive treatment. This study serves to remind clinicians of the limitations of margin assessment and provides impetus for dermatopathologists to consider modifying how margin status is reported.

Limitations of this study include a small number of cases and limited generalizability. Institutions that routinely examine more levels of each biopsy specimen may be less likely to erroneously categorize a positive margin as negative. Furthermore, despite exhausting the tissue block, we still may have underestimated the number of cases with truly positive margins, as this method inherently does not allow for complete margin examination.

Acknowledgments
We thank the Geisinger Department of Dermatopathology and the Geisinger Biostatistics & Research Data Core (Danville, Pennsylvania) for their assistance with our project.

Basal cell carcinoma (BCC) is the most common type of skin cancer frequently encountered in both dermatology and primary care settings.¹ When biopsies of these neoplasms are performed to confirm the diagnosis, pathology reports may indicate positive or negative margin status. No guidelines exist for reporting biopsy margin status for BCC, resulting in varied reporting practices among dermatopathologists. Furthermore, the terminology used to describe margin status can be ambiguous and differs among pathologists; language such as “approaches the margin” or “margins appear free” may be used, with nonuniform interpretation between pathologists and providers, leading to variability in patient management.²

When interpreting a negative margin status on a pathology report, one must question if the BCC extends beyond the margin in unexamined sections of the specimen, which could be the result of an irregular tumor growth pattern or tissue processing. It has been estimated that less than 2% of the peripheral surgical margin is ultimately examined when serial cross-sections are prepared histologically (the bread loaf technique). However, this estimation would depend on several variables, including the number and thickness of sections and the amount of tissue discarded during processing.³ Importantly, reports of a false-negative margin could lead both the clinician and patient to believe that the neoplasm has been completely removed, which could have serious consequences.

Our study sought to determine the reliability of negative biopsy margin status for BCC. We examined BCC biopsy specimens initially determined to have uninvolved margins on routine tissue processing and determined the proportion with truly negative margins after complete tissue block sectioning of the initial biopsy specimen. We felt this technique was a more accurate measurement of true margin status than examination of a re-excision specimen. We also identified any factors that were predictive of positive true margins.

Methods

We conducted a retrospective study evaluating tissue samples collected at Geisinger Health System (Danville, Pennsylvania) from January to December 2016. Specimens were queried via the electronic database system at our institution (CoPath). We included BCC biopsy specimens with negative histologic margins on initial assessment that subsequently had block exhaust levels routinely ordered. These levels are cut every 100 to 150 µm, generating approximately 8 glass slides. We excluded all tumors that did not fit these criteria as well as those in patients younger than 18 years. Data collection was performed utilizing specimen pathology reports in addition to the note from the corresponding clinician office visit from the institution’s electronic medical record (Epic). Appropriate statistical calculations were performed. This study was approved by an institutional review board at our institution, which is required for all research involving human participants. This served to ensure the proper review and storage of patients’ protected health information.

Results

The search yielded a total of 122 specimens from 104 patients after appropriate exclusions. We examined a total of 122 BCC biopsy specimens with negative initial margins: 121 (99.2%) shave biopsies and 1 (0.8%) punch biopsy. Of 122 specimens with negative initial margins, 53 (43.4%) were found to have a truly positive margin based on the presence of either tumor or stroma at the lateral or deep tissue edge after complete tissue block sectioning. Sixty-nine (56.6%) specimens had clear margins and were categorized as truly negative after complete tissue block sectioning. Specimens with positive and negative final margin status did not differ significantly with respect to patient age; gender; biopsy technique; number of gross specimen sections; or tumor characteristics, including location, size, and subtype (Table)(P>.05).

We also examined the type of treatment performed, which varied and included curettage, electrodesiccation and curettage, excision, and Mohs micrographic surgery. Clinicians, who were not made aware of the exhaust level protocol, chose not to pursue further treatment in 6 (4.9%) of the cases because of negative biopsy margins. Four (66.7%) of the 6 providers were physicians, and 2 (33.3%) were advanced practitioners. All of the providers practiced within the Department of Dermatology.

Comment

Our findings support prior smaller studies investigating this topic. A prospective study by Schnebelen et al⁴ examined 27 BCC biopsy specimens and found that 8 (30%) were erroneously classified as negative on routine examination. This study similarly determined true margin status by assessing the margins at complete tissue block exhaustion.⁴ Willardson et al⁵ also demonstrated the poor predictive value of margin status based on the presence of residual BCC in subsequent excisions. They found that 34 (24%) of 143 cases with negative biopsy margins contained residual tumor in the corresponding excision.⁵

Our study revealed that almost half of BCC biopsy specimens that had negative histologic margins with routine sectioning had truly positive margins on complete block exhaustion. This finding was independent of multiple factors, including tumor subtype, indicating that even nonaggressive tumors are prone to false-negative margin reports. We also found that reports of negative margins persuaded some clinicians to forgo definitive treatment. This study serves to remind clinicians of the limitations of margin assessment and provides impetus for dermatopathologists to consider modifying how margin status is reported.

Limitations of this study include a small number of cases and limited generalizability. Institutions that routinely examine more levels of each biopsy specimen may be less likely to erroneously categorize a positive margin as negative. Furthermore, despite exhausting the tissue block, we still may have underestimated the number of cases with truly positive margins, as this method inherently does not allow for complete margin examination.

Acknowledgments
We thank the Geisinger Department of Dermatopathology and the Geisinger Biostatistics & Research Data Core (Danville, Pennsylvania) for their assistance with our project.

To the Editor:

A 32-year-old man presented to the dermatology clinic with multiple asymptomatic blue lesions on the arms and upper torso of 15 years’ duration. His medical history was notable for a recent diagnosis of malignant melanoma following excision of a mole on the upper back 4 months prior. He reported that the mole had been present since childhood, but his sister noticed that it increased in size and changed in color over the course of a year. Physical examination showed multiple blue subcutaneous nodules on the bilateral arms and lower back. The nodules were soft and nontender, and some had telangiectasia on the overlying skin.

Given the atypical distribution of nodules and the patient’s recent history of melanoma, there was concern for cutaneous metastases. A punch biopsy of one of the nodules on the right upper arm was performed. Microscopic examination of the biopsy specimen revealed a proliferation of multiple cavernous vessels surrounded by several rows of monotonous round cells with moderate eosinophilic cytoplasm and monomorphic nuclei, which was consistent with a diagnosis of glomangioma (Figure 1). Immunohistochemical analysis showed diffuse positive staining for smooth muscle actin (Figure 2); CD34 immunostain was positive in endothelial cells and negative in tumor cells (Figure 3).

Glomus tumors arise from modified smooth muscle cells located in glomus bodies. The glomus body is a component of the dermis involved in regulation of body temperature that is composed of an afferent arteriole and an efferent venule. The arterial end of this apparatus, known as the Sucquet-Hoyer canal, is surrounded by glomus cells that have a contractile capability similar to smooth muscle cells. Glomus tumors usually present as painful masses on the fingers with a typical subungual location and almost always are solitary.¹ Glomangiomas, sometimes known as glomuvenous malformations, tend to be larger and usually are painless. They mostly are found on the trunk and extremities and can appear in groups.^2,3 Histopathologically, glomus tumors are circumscribed lesions that show a predominance of glomus cells surrounding inconspicuous blood vessels. Glomangiomas are less well-circumscribed and show a more vascular architecture with prominent dilated vessels and a smaller number of glomus cells.⁴

We present a case of a patient with multiple glomangiomas. There are few reports of multiple glomangiomas in the literature. This case is particularly interesting in that our patient had a history of malignant melanoma, and there was a concern for skin metastases. Despite the patient’s personal history of blue lesions that predated the diagnosis of melanoma for many years, we could not exclude the possibility of cutaneous metastases without performing biopsies.

Tumors of glomus cell origin usually are benign. It has been suggested to replace the term glomangioma with glomuvenous malformations to emphasize the hamartomatous nature of these lesions.⁵ Glomuvenous malformations, or glomangiomas, can occur sporadically or can be inherited as a familial disorder. Inheritable glomangioma has been linked to the chromosome 1p21-22 locus and mutations in the glomulin gene, GLMN, with variable penetrance.⁶ Our patient did not report a family history of such lesions.

Glomangiomas typically are solitary but rarely can present as multiple lesions in fewer than 10% of cases.⁷ Multiple glomangiomas are classified into 3 subtypes: localized, disseminated, and congenital plaque type. Localized multiple glomangiomas present as blue nodules confined to 1 anatomic location such as the hand or arm. Disseminated glomangiomas are more widely distributed and involve more than 1 anatomic location.⁸ Plaque-type glomangiomas consist of numerous confluent lesions occurring either as solitary or multiple plaques.² Clinically, glomangiomas manifest as painless to mildly painful cutaneous nodules. Compared to venous malformations, glomangiomas are less compressible under external pressure.

Histopathologically, glomangiomas appear as nonencapsulated tumors with large, irregular, prominent vessels lined by glomus cells. Glomus cells may be so sparse that the distinction from venous malformations and hemangiomas becomes difficult. Immunohistochemistry can play an important role in diagnosis. As modified smooth muscle cells, glomus cells stain positive with a-smooth muscle actin, while CD34 highlights the vascular endothelium.¹The clinical differential diagnosis of multiple blue or violaceous subcutaneous nodules includes blue rubber bleb nevus syndrome, Maffucci syndrome, glomus tumor, pyogenic granuloma, hemangioma, spiradenoma, angiolipoma, leiomyoma, or hemangiopericytoma.^9-12

Different treatment modalities are available for solitary glomangiomas, including surgical excision, sclerotherapy, and laser application. Treatment of multiple glomangiomas may not be feasible, and excision of isolated symptomatic lesions may be the only option; however, it is crucial to reach the correct diagnosis in these patients to avoid improper treatments and interventions.

To the Editor:

A 32-year-old man presented to the dermatology clinic with multiple asymptomatic blue lesions on the arms and upper torso of 15 years’ duration. His medical history was notable for a recent diagnosis of malignant melanoma following excision of a mole on the upper back 4 months prior. He reported that the mole had been present since childhood, but his sister noticed that it increased in size and changed in color over the course of a year. Physical examination showed multiple blue subcutaneous nodules on the bilateral arms and lower back. The nodules were soft and nontender, and some had telangiectasia on the overlying skin.

Given the atypical distribution of nodules and the patient’s recent history of melanoma, there was concern for cutaneous metastases. A punch biopsy of one of the nodules on the right upper arm was performed. Microscopic examination of the biopsy specimen revealed a proliferation of multiple cavernous vessels surrounded by several rows of monotonous round cells with moderate eosinophilic cytoplasm and monomorphic nuclei, which was consistent with a diagnosis of glomangioma (Figure 1). Immunohistochemical analysis showed diffuse positive staining for smooth muscle actin (Figure 2); CD34 immunostain was positive in endothelial cells and negative in tumor cells (Figure 3).

Glomus tumors arise from modified smooth muscle cells located in glomus bodies. The glomus body is a component of the dermis involved in regulation of body temperature that is composed of an afferent arteriole and an efferent venule. The arterial end of this apparatus, known as the Sucquet-Hoyer canal, is surrounded by glomus cells that have a contractile capability similar to smooth muscle cells. Glomus tumors usually present as painful masses on the fingers with a typical subungual location and almost always are solitary.¹ Glomangiomas, sometimes known as glomuvenous malformations, tend to be larger and usually are painless. They mostly are found on the trunk and extremities and can appear in groups.^2,3 Histopathologically, glomus tumors are circumscribed lesions that show a predominance of glomus cells surrounding inconspicuous blood vessels. Glomangiomas are less well-circumscribed and show a more vascular architecture with prominent dilated vessels and a smaller number of glomus cells.⁴

We present a case of a patient with multiple glomangiomas. There are few reports of multiple glomangiomas in the literature. This case is particularly interesting in that our patient had a history of malignant melanoma, and there was a concern for skin metastases. Despite the patient’s personal history of blue lesions that predated the diagnosis of melanoma for many years, we could not exclude the possibility of cutaneous metastases without performing biopsies.

Tumors of glomus cell origin usually are benign. It has been suggested to replace the term glomangioma with glomuvenous malformations to emphasize the hamartomatous nature of these lesions.⁵ Glomuvenous malformations, or glomangiomas, can occur sporadically or can be inherited as a familial disorder. Inheritable glomangioma has been linked to the chromosome 1p21-22 locus and mutations in the glomulin gene, GLMN, with variable penetrance.⁶ Our patient did not report a family history of such lesions.

Glomangiomas typically are solitary but rarely can present as multiple lesions in fewer than 10% of cases.⁷ Multiple glomangiomas are classified into 3 subtypes: localized, disseminated, and congenital plaque type. Localized multiple glomangiomas present as blue nodules confined to 1 anatomic location such as the hand or arm. Disseminated glomangiomas are more widely distributed and involve more than 1 anatomic location.⁸ Plaque-type glomangiomas consist of numerous confluent lesions occurring either as solitary or multiple plaques.² Clinically, glomangiomas manifest as painless to mildly painful cutaneous nodules. Compared to venous malformations, glomangiomas are less compressible under external pressure.

Histopathologically, glomangiomas appear as nonencapsulated tumors with large, irregular, prominent vessels lined by glomus cells. Glomus cells may be so sparse that the distinction from venous malformations and hemangiomas becomes difficult. Immunohistochemistry can play an important role in diagnosis. As modified smooth muscle cells, glomus cells stain positive with a-smooth muscle actin, while CD34 highlights the vascular endothelium.¹The clinical differential diagnosis of multiple blue or violaceous subcutaneous nodules includes blue rubber bleb nevus syndrome, Maffucci syndrome, glomus tumor, pyogenic granuloma, hemangioma, spiradenoma, angiolipoma, leiomyoma, or hemangiopericytoma.^9-12

Different treatment modalities are available for solitary glomangiomas, including surgical excision, sclerotherapy, and laser application. Treatment of multiple glomangiomas may not be feasible, and excision of isolated symptomatic lesions may be the only option; however, it is crucial to reach the correct diagnosis in these patients to avoid improper treatments and interventions.

To the Editor:

A 32-year-old man presented to the dermatology clinic with multiple asymptomatic blue lesions on the arms and upper torso of 15 years’ duration. His medical history was notable for a recent diagnosis of malignant melanoma following excision of a mole on the upper back 4 months prior. He reported that the mole had been present since childhood, but his sister noticed that it increased in size and changed in color over the course of a year. Physical examination showed multiple blue subcutaneous nodules on the bilateral arms and lower back. The nodules were soft and nontender, and some had telangiectasia on the overlying skin.

Given the atypical distribution of nodules and the patient’s recent history of melanoma, there was concern for cutaneous metastases. A punch biopsy of one of the nodules on the right upper arm was performed. Microscopic examination of the biopsy specimen revealed a proliferation of multiple cavernous vessels surrounded by several rows of monotonous round cells with moderate eosinophilic cytoplasm and monomorphic nuclei, which was consistent with a diagnosis of glomangioma (Figure 1). Immunohistochemical analysis showed diffuse positive staining for smooth muscle actin (Figure 2); CD34 immunostain was positive in endothelial cells and negative in tumor cells (Figure 3).

Glomus tumors arise from modified smooth muscle cells located in glomus bodies. The glomus body is a component of the dermis involved in regulation of body temperature that is composed of an afferent arteriole and an efferent venule. The arterial end of this apparatus, known as the Sucquet-Hoyer canal, is surrounded by glomus cells that have a contractile capability similar to smooth muscle cells. Glomus tumors usually present as painful masses on the fingers with a typical subungual location and almost always are solitary.¹ Glomangiomas, sometimes known as glomuvenous malformations, tend to be larger and usually are painless. They mostly are found on the trunk and extremities and can appear in groups.^2,3 Histopathologically, glomus tumors are circumscribed lesions that show a predominance of glomus cells surrounding inconspicuous blood vessels. Glomangiomas are less well-circumscribed and show a more vascular architecture with prominent dilated vessels and a smaller number of glomus cells.⁴

We present a case of a patient with multiple glomangiomas. There are few reports of multiple glomangiomas in the literature. This case is particularly interesting in that our patient had a history of malignant melanoma, and there was a concern for skin metastases. Despite the patient’s personal history of blue lesions that predated the diagnosis of melanoma for many years, we could not exclude the possibility of cutaneous metastases without performing biopsies.

Tumors of glomus cell origin usually are benign. It has been suggested to replace the term glomangioma with glomuvenous malformations to emphasize the hamartomatous nature of these lesions.⁵ Glomuvenous malformations, or glomangiomas, can occur sporadically or can be inherited as a familial disorder. Inheritable glomangioma has been linked to the chromosome 1p21-22 locus and mutations in the glomulin gene, GLMN, with variable penetrance.⁶ Our patient did not report a family history of such lesions.

Glomangiomas typically are solitary but rarely can present as multiple lesions in fewer than 10% of cases.⁷ Multiple glomangiomas are classified into 3 subtypes: localized, disseminated, and congenital plaque type. Localized multiple glomangiomas present as blue nodules confined to 1 anatomic location such as the hand or arm. Disseminated glomangiomas are more widely distributed and involve more than 1 anatomic location.⁸ Plaque-type glomangiomas consist of numerous confluent lesions occurring either as solitary or multiple plaques.² Clinically, glomangiomas manifest as painless to mildly painful cutaneous nodules. Compared to venous malformations, glomangiomas are less compressible under external pressure.

Histopathologically, glomangiomas appear as nonencapsulated tumors with large, irregular, prominent vessels lined by glomus cells. Glomus cells may be so sparse that the distinction from venous malformations and hemangiomas becomes difficult. Immunohistochemistry can play an important role in diagnosis. As modified smooth muscle cells, glomus cells stain positive with a-smooth muscle actin, while CD34 highlights the vascular endothelium.¹The clinical differential diagnosis of multiple blue or violaceous subcutaneous nodules includes blue rubber bleb nevus syndrome, Maffucci syndrome, glomus tumor, pyogenic granuloma, hemangioma, spiradenoma, angiolipoma, leiomyoma, or hemangiopericytoma.^9-12

Different treatment modalities are available for solitary glomangiomas, including surgical excision, sclerotherapy, and laser application. Treatment of multiple glomangiomas may not be feasible, and excision of isolated symptomatic lesions may be the only option; however, it is crucial to reach the correct diagnosis in these patients to avoid improper treatments and interventions.

The Diagnosis: Piloleiomyoma 

Leiomyoma cutis, also known as cutaneous leiomyoma, is a benign smooth muscle tumor first described in 1854.¹ Cutaneous leiomyoma is comprised of 3 distinct types that depend on the origin of smooth muscle tumor: piloleiomyoma (arrector pili muscle), angioleiomyoma (tunica media of arteries/veins), and genital leiomyoma (dartos muscle of the scrotum and labia majora, erectile muscle of nipple).² It affects both sexes equally, though some reports have noted an increased prevalence in females. Piloleiomyomas commonly present on the extensor surfaces of the extremities (solitary) and trunk (multiple).¹ Tumors most often present as firm flesh-colored or pink-brown papulonodules. They can be linear, dermatomal, segmental, or diffuse, and often are painful. Clinical differential diagnosis for painful skin tumors is aided by the acronym "BLEND AN EGG": blue rubber bleb nevus, leiomyoma, eccrine spiradenoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, endometrioma, glomangioma, and granular cell tumor.³ For isolated lesions, surgical excision is the treatment of choice. For numerous lesions in which excision would not be feasible, intralesional corticosteroids, medications (eg, calcium channel blockers, alpha blockers, nitroglycerin), and botulinum toxin have been used for pain relief.⁴  

Notably, multiple cutaneous leiomyomas can be seen in association with uterine leiomyomas in Reed syndrome due to an autosomal-dominant or de novo mutation in the fumarate hydratase gene, FH. Reed syndrome is associated with a lifetime risk for renal cell carcinoma (hereditary leiomyomatosis and renal cell cancer) in 15% of cases with FH mutations.⁵ In our patient, both immunohistochemical staining and blood testing for FH were performed. Immunohistochemistry revealed notably diminished staining with only weak patchy granular cytoplasmic staining present (Figure 1). Genetic testing revealed heterozygosity for a pathogenic variant of the FH gene, consistent with a diagnosis of Reed syndrome.  

Histologically, the differential diagnosis includes other spindle cell tumors, such as dermatofibroma, neurofibroma, and dermatomyofibroma. The histologic appearance varies depending on the type, with piloleiomyoma typically located within the reticular dermis with possible subcutaneous extension. Fascicles of eosinophilic smooth muscle cells in an interlacing arrangement often ramify between neighboring dermal collagen; these smooth muscle cells contain cigar-shaped, blunt-ended nuclei with a perinuclear clear vacuole. Marked epidermal hyperplasia is possible.⁶ A close association with a nearby hair follicle frequently is noted. Although differentiated smooth muscle cells usually are evident on hematoxylin and eosin, positive staining for smooth muscle actin (SMA) and desmin can aid in diagnosis.⁷ Immunohistochemical staining for FH has proven to be highly specific (97.6%) with moderate sensitivity (70.0%).⁸ Angioleiomyomas appear as well-demarcated dermal to subcutaneous tumors composed of smooth muscle cells surrounding thick-walled vaculature.⁹ Scrotal and vulvar leiomyomas are composed of eosinophilic spindle cells, though vulvar leiomyomas have shown epithelioid differentiation.¹⁰ Nipple leiomyomas appear similar to piloleiomyomas on histology with interlacing smooth muscle fiber bundles.  

Eccrine spiradenoma is a relatively uncommon adnexal tumor derived from eccrine sweat glands. It most often presents as a small, painful or tender, intradermal nodule (or rarely as nodules) on the head or ventral trunk.¹¹ There is no sexual predilection. It affects adults at any age but most often from 15 to 35 years. Although rare, malignant transformation is possible. Histologically, eccrine spiradenomas appear as a well-demarcated dermal tumor composed of bland basaloid cells with minimal cytoplasm, often with numerous admixed lymphocytes and variably prominent vasculature (Figure 2). Eosinophilic basement membrane material can be seen within or surrounding the nodules of tumor cells. Multiple spiradenomas can occur in the setting of Brooke-Spiegler syndrome, which is an autosomal-dominant disorder due to an inherited mutation in the CYLD gene. Spiradenomas are benign neoplasms, and surgical excision with clear margins is the treatment of choice.¹²  

Dermatofibroma, also known as cutaneous benign fibrous histiocytoma, is a firm, flesh-colored papule or nodule that most often presents on the lower extremities. It typically is seen in women aged 20 to 40 years.¹³ The etiology is uncertain, and dermatofibromas often spontaneously develop, though there are inconsistent reports of development with local trauma including insect bites and puncture wounds. The dimple sign refers to skin dimpling with lateral pressure.¹³ Most commonly, dermatofibromas consist of a dermal proliferation of bland fibroblastic cells with entrapment of dermal collagen bundles at the periphery of the tumors (Figure 3). The fibroblastic cells often are paler and less eosinophilic than smooth muscle cells seen in cutaneous leiomyomas, with tapered nuclei that lack a perinuclear vacuole. Admixed histocytes and other inflammatory cells often are present. Overlying epidermal hyperplasia and/or hyperpigmentation also may be present. Numerous histologic variants have been described, including cellular, epithelioid, aneurysmal, atypical, and hemosiderotic types.¹⁴ Immunohistochemical stains may show patchy positive staining for SMA, but h-caldesmon and desmin typically are negative.  

Neurofibroma is a tumor derived from neuromesenchymal tissue with nerve axons. They form through neuromesenchyme (eg, Schwann cells, mast cells, perineural cells, endoneural fibroblast) proliferation. Solitary neurofibromas occur most commonly in adults and have no gender predilection. The most common presentation is an asymptomatic, solitary, soft, flesh-colored papulonodule.¹⁵ Clinical variants include pigmented, diffuse, and plexiform, with plexiform neurofibromas almost always being consistent with a diagnosis of neurofibromatosis type 1. Histologically, neurofibromas present as dermal or subcutaneous nodules composed of randomly arranged spindle cells with wavy tapered nuclei within a loose collagenous stroma (Figure 4).¹⁶ The spindle cells in neurofibromas will stain positively for S-100 protein and SOX-10 and negatively for SMA and desmin.  

Angiolipoma is a benign tumor composed of adipocytes that also contains vasculature.¹⁷ The majority of cases are of unknown etiology, though familial cases have been described. They typically present as multiple painful or tender (differentiating from lipomas) subcutaneous swellings over the forearms in individuals aged 20 to 30 years.¹⁸ On histopathology, angiolipomas appear as well-circumscribed subcutaneous tumors containing mature adipocytes intermixed with small capillary vessels, some of which contain luminal fibrin thrombi (Figure 5).  

The Diagnosis: Piloleiomyoma 

Leiomyoma cutis, also known as cutaneous leiomyoma, is a benign smooth muscle tumor first described in 1854.¹ Cutaneous leiomyoma is comprised of 3 distinct types that depend on the origin of smooth muscle tumor: piloleiomyoma (arrector pili muscle), angioleiomyoma (tunica media of arteries/veins), and genital leiomyoma (dartos muscle of the scrotum and labia majora, erectile muscle of nipple).² It affects both sexes equally, though some reports have noted an increased prevalence in females. Piloleiomyomas commonly present on the extensor surfaces of the extremities (solitary) and trunk (multiple).¹ Tumors most often present as firm flesh-colored or pink-brown papulonodules. They can be linear, dermatomal, segmental, or diffuse, and often are painful. Clinical differential diagnosis for painful skin tumors is aided by the acronym "BLEND AN EGG": blue rubber bleb nevus, leiomyoma, eccrine spiradenoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, endometrioma, glomangioma, and granular cell tumor.³ For isolated lesions, surgical excision is the treatment of choice. For numerous lesions in which excision would not be feasible, intralesional corticosteroids, medications (eg, calcium channel blockers, alpha blockers, nitroglycerin), and botulinum toxin have been used for pain relief.⁴  

Notably, multiple cutaneous leiomyomas can be seen in association with uterine leiomyomas in Reed syndrome due to an autosomal-dominant or de novo mutation in the fumarate hydratase gene, FH. Reed syndrome is associated with a lifetime risk for renal cell carcinoma (hereditary leiomyomatosis and renal cell cancer) in 15% of cases with FH mutations.⁵ In our patient, both immunohistochemical staining and blood testing for FH were performed. Immunohistochemistry revealed notably diminished staining with only weak patchy granular cytoplasmic staining present (Figure 1). Genetic testing revealed heterozygosity for a pathogenic variant of the FH gene, consistent with a diagnosis of Reed syndrome.  

Histologically, the differential diagnosis includes other spindle cell tumors, such as dermatofibroma, neurofibroma, and dermatomyofibroma. The histologic appearance varies depending on the type, with piloleiomyoma typically located within the reticular dermis with possible subcutaneous extension. Fascicles of eosinophilic smooth muscle cells in an interlacing arrangement often ramify between neighboring dermal collagen; these smooth muscle cells contain cigar-shaped, blunt-ended nuclei with a perinuclear clear vacuole. Marked epidermal hyperplasia is possible.⁶ A close association with a nearby hair follicle frequently is noted. Although differentiated smooth muscle cells usually are evident on hematoxylin and eosin, positive staining for smooth muscle actin (SMA) and desmin can aid in diagnosis.⁷ Immunohistochemical staining for FH has proven to be highly specific (97.6%) with moderate sensitivity (70.0%).⁸ Angioleiomyomas appear as well-demarcated dermal to subcutaneous tumors composed of smooth muscle cells surrounding thick-walled vaculature.⁹ Scrotal and vulvar leiomyomas are composed of eosinophilic spindle cells, though vulvar leiomyomas have shown epithelioid differentiation.¹⁰ Nipple leiomyomas appear similar to piloleiomyomas on histology with interlacing smooth muscle fiber bundles.  

Eccrine spiradenoma is a relatively uncommon adnexal tumor derived from eccrine sweat glands. It most often presents as a small, painful or tender, intradermal nodule (or rarely as nodules) on the head or ventral trunk.¹¹ There is no sexual predilection. It affects adults at any age but most often from 15 to 35 years. Although rare, malignant transformation is possible. Histologically, eccrine spiradenomas appear as a well-demarcated dermal tumor composed of bland basaloid cells with minimal cytoplasm, often with numerous admixed lymphocytes and variably prominent vasculature (Figure 2). Eosinophilic basement membrane material can be seen within or surrounding the nodules of tumor cells. Multiple spiradenomas can occur in the setting of Brooke-Spiegler syndrome, which is an autosomal-dominant disorder due to an inherited mutation in the CYLD gene. Spiradenomas are benign neoplasms, and surgical excision with clear margins is the treatment of choice.¹²  

Dermatofibroma, also known as cutaneous benign fibrous histiocytoma, is a firm, flesh-colored papule or nodule that most often presents on the lower extremities. It typically is seen in women aged 20 to 40 years.¹³ The etiology is uncertain, and dermatofibromas often spontaneously develop, though there are inconsistent reports of development with local trauma including insect bites and puncture wounds. The dimple sign refers to skin dimpling with lateral pressure.¹³ Most commonly, dermatofibromas consist of a dermal proliferation of bland fibroblastic cells with entrapment of dermal collagen bundles at the periphery of the tumors (Figure 3). The fibroblastic cells often are paler and less eosinophilic than smooth muscle cells seen in cutaneous leiomyomas, with tapered nuclei that lack a perinuclear vacuole. Admixed histocytes and other inflammatory cells often are present. Overlying epidermal hyperplasia and/or hyperpigmentation also may be present. Numerous histologic variants have been described, including cellular, epithelioid, aneurysmal, atypical, and hemosiderotic types.¹⁴ Immunohistochemical stains may show patchy positive staining for SMA, but h-caldesmon and desmin typically are negative.  

Neurofibroma is a tumor derived from neuromesenchymal tissue with nerve axons. They form through neuromesenchyme (eg, Schwann cells, mast cells, perineural cells, endoneural fibroblast) proliferation. Solitary neurofibromas occur most commonly in adults and have no gender predilection. The most common presentation is an asymptomatic, solitary, soft, flesh-colored papulonodule.¹⁵ Clinical variants include pigmented, diffuse, and plexiform, with plexiform neurofibromas almost always being consistent with a diagnosis of neurofibromatosis type 1. Histologically, neurofibromas present as dermal or subcutaneous nodules composed of randomly arranged spindle cells with wavy tapered nuclei within a loose collagenous stroma (Figure 4).¹⁶ The spindle cells in neurofibromas will stain positively for S-100 protein and SOX-10 and negatively for SMA and desmin.  

Angiolipoma is a benign tumor composed of adipocytes that also contains vasculature.¹⁷ The majority of cases are of unknown etiology, though familial cases have been described. They typically present as multiple painful or tender (differentiating from lipomas) subcutaneous swellings over the forearms in individuals aged 20 to 30 years.¹⁸ On histopathology, angiolipomas appear as well-circumscribed subcutaneous tumors containing mature adipocytes intermixed with small capillary vessels, some of which contain luminal fibrin thrombi (Figure 5).  

The Diagnosis: Piloleiomyoma 

Leiomyoma cutis, also known as cutaneous leiomyoma, is a benign smooth muscle tumor first described in 1854.¹ Cutaneous leiomyoma is comprised of 3 distinct types that depend on the origin of smooth muscle tumor: piloleiomyoma (arrector pili muscle), angioleiomyoma (tunica media of arteries/veins), and genital leiomyoma (dartos muscle of the scrotum and labia majora, erectile muscle of nipple).² It affects both sexes equally, though some reports have noted an increased prevalence in females. Piloleiomyomas commonly present on the extensor surfaces of the extremities (solitary) and trunk (multiple).¹ Tumors most often present as firm flesh-colored or pink-brown papulonodules. They can be linear, dermatomal, segmental, or diffuse, and often are painful. Clinical differential diagnosis for painful skin tumors is aided by the acronym "BLEND AN EGG": blue rubber bleb nevus, leiomyoma, eccrine spiradenoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, endometrioma, glomangioma, and granular cell tumor.³ For isolated lesions, surgical excision is the treatment of choice. For numerous lesions in which excision would not be feasible, intralesional corticosteroids, medications (eg, calcium channel blockers, alpha blockers, nitroglycerin), and botulinum toxin have been used for pain relief.⁴  

Notably, multiple cutaneous leiomyomas can be seen in association with uterine leiomyomas in Reed syndrome due to an autosomal-dominant or de novo mutation in the fumarate hydratase gene, FH. Reed syndrome is associated with a lifetime risk for renal cell carcinoma (hereditary leiomyomatosis and renal cell cancer) in 15% of cases with FH mutations.⁵ In our patient, both immunohistochemical staining and blood testing for FH were performed. Immunohistochemistry revealed notably diminished staining with only weak patchy granular cytoplasmic staining present (Figure 1). Genetic testing revealed heterozygosity for a pathogenic variant of the FH gene, consistent with a diagnosis of Reed syndrome.  

Histologically, the differential diagnosis includes other spindle cell tumors, such as dermatofibroma, neurofibroma, and dermatomyofibroma. The histologic appearance varies depending on the type, with piloleiomyoma typically located within the reticular dermis with possible subcutaneous extension. Fascicles of eosinophilic smooth muscle cells in an interlacing arrangement often ramify between neighboring dermal collagen; these smooth muscle cells contain cigar-shaped, blunt-ended nuclei with a perinuclear clear vacuole. Marked epidermal hyperplasia is possible.⁶ A close association with a nearby hair follicle frequently is noted. Although differentiated smooth muscle cells usually are evident on hematoxylin and eosin, positive staining for smooth muscle actin (SMA) and desmin can aid in diagnosis.⁷ Immunohistochemical staining for FH has proven to be highly specific (97.6%) with moderate sensitivity (70.0%).⁸ Angioleiomyomas appear as well-demarcated dermal to subcutaneous tumors composed of smooth muscle cells surrounding thick-walled vaculature.⁹ Scrotal and vulvar leiomyomas are composed of eosinophilic spindle cells, though vulvar leiomyomas have shown epithelioid differentiation.¹⁰ Nipple leiomyomas appear similar to piloleiomyomas on histology with interlacing smooth muscle fiber bundles.  

Eccrine spiradenoma is a relatively uncommon adnexal tumor derived from eccrine sweat glands. It most often presents as a small, painful or tender, intradermal nodule (or rarely as nodules) on the head or ventral trunk.¹¹ There is no sexual predilection. It affects adults at any age but most often from 15 to 35 years. Although rare, malignant transformation is possible. Histologically, eccrine spiradenomas appear as a well-demarcated dermal tumor composed of bland basaloid cells with minimal cytoplasm, often with numerous admixed lymphocytes and variably prominent vasculature (Figure 2). Eosinophilic basement membrane material can be seen within or surrounding the nodules of tumor cells. Multiple spiradenomas can occur in the setting of Brooke-Spiegler syndrome, which is an autosomal-dominant disorder due to an inherited mutation in the CYLD gene. Spiradenomas are benign neoplasms, and surgical excision with clear margins is the treatment of choice.¹²  

Dermatofibroma, also known as cutaneous benign fibrous histiocytoma, is a firm, flesh-colored papule or nodule that most often presents on the lower extremities. It typically is seen in women aged 20 to 40 years.¹³ The etiology is uncertain, and dermatofibromas often spontaneously develop, though there are inconsistent reports of development with local trauma including insect bites and puncture wounds. The dimple sign refers to skin dimpling with lateral pressure.¹³ Most commonly, dermatofibromas consist of a dermal proliferation of bland fibroblastic cells with entrapment of dermal collagen bundles at the periphery of the tumors (Figure 3). The fibroblastic cells often are paler and less eosinophilic than smooth muscle cells seen in cutaneous leiomyomas, with tapered nuclei that lack a perinuclear vacuole. Admixed histocytes and other inflammatory cells often are present. Overlying epidermal hyperplasia and/or hyperpigmentation also may be present. Numerous histologic variants have been described, including cellular, epithelioid, aneurysmal, atypical, and hemosiderotic types.¹⁴ Immunohistochemical stains may show patchy positive staining for SMA, but h-caldesmon and desmin typically are negative.  

Neurofibroma is a tumor derived from neuromesenchymal tissue with nerve axons. They form through neuromesenchyme (eg, Schwann cells, mast cells, perineural cells, endoneural fibroblast) proliferation. Solitary neurofibromas occur most commonly in adults and have no gender predilection. The most common presentation is an asymptomatic, solitary, soft, flesh-colored papulonodule.¹⁵ Clinical variants include pigmented, diffuse, and plexiform, with plexiform neurofibromas almost always being consistent with a diagnosis of neurofibromatosis type 1. Histologically, neurofibromas present as dermal or subcutaneous nodules composed of randomly arranged spindle cells with wavy tapered nuclei within a loose collagenous stroma (Figure 4).¹⁶ The spindle cells in neurofibromas will stain positively for S-100 protein and SOX-10 and negatively for SMA and desmin.  

Angiolipoma is a benign tumor composed of adipocytes that also contains vasculature.¹⁷ The majority of cases are of unknown etiology, though familial cases have been described. They typically present as multiple painful or tender (differentiating from lipomas) subcutaneous swellings over the forearms in individuals aged 20 to 30 years.¹⁸ On histopathology, angiolipomas appear as well-circumscribed subcutaneous tumors containing mature adipocytes intermixed with small capillary vessels, some of which contain luminal fibrin thrombi (Figure 5).  

To the Editor:

Lichen sclerosus is a chronic inflammatory skin disease of unknown cause that predominantly affects the anogenital region, but isolated extragenital lesions occur in 6% to 15% of patients. The buttocks, thighs, neck, shoulder, upper torso, and wrists most commonly are involved; the face rarely is affected.^1,2 Although the etiology of lichen sclerosus remains undetermined, there is growing evidence that autoimmunity may play a role.¹ Lichen sclerosus more commonly is seen in women, and the disease can present at any age, with a bimodal onset in prepubertal children and in postmenopausal women and men in the fourth decade of life.^1-3 A PubMed search of articles indexed for MEDLINE using the terms lichen and eyelid and manually screened revealed 6 cases of lichen sclerosus involving the eyelid.^2-4 We describe a case of lichen sclerosus involving the eyelid and its histopathology.

A 45-year-old woman was referred to dermatology for evaluation of a right lower eyelid lesion of 3 months’ duration. She first noted a small white patch under the eyelid that had doubled in size and felt firm without bleeding or ulceration. Her medical history was unremarkable, and there was no history of ophthalmic conditions, autoimmune disease, trauma, or cancer. An ophthalmic examination was normal, except for a 20×8-mm, flat, depigmented, firm papule with scalloped borders involving the right lower eyelid margin and extending inferiorly without evidence of madarosis or ulceration (Figure 1). She underwent an incisional biopsy that revealed the diagnosis of lichen sclerosus et atrophicus (Figure 2). A full dermatologic evaluation included a genital examination and did not reveal any additional lesions. Tacrolimus ointment was started to avoid the need for long-term use of periocular steroids and their complications.

Histopathology is useful to distinguish among these entities. Although there are no specific features separating lichen sclerosus from a morphea overlap and both entities often are classified by clinical presentation, lichen sclerosus demonstrates epidermal atrophy, follicular plugging, homogenized collagen in the upper dermis with dermal edema, and lichenoid lymphocytic infiltrate (Figure 2).¹ Extragenital lesions in particular also have been noted to have more epidermal atrophy and decreased rete ridges.²

To the Editor:

Lichen sclerosus is a chronic inflammatory skin disease of unknown cause that predominantly affects the anogenital region, but isolated extragenital lesions occur in 6% to 15% of patients. The buttocks, thighs, neck, shoulder, upper torso, and wrists most commonly are involved; the face rarely is affected.^1,2 Although the etiology of lichen sclerosus remains undetermined, there is growing evidence that autoimmunity may play a role.¹ Lichen sclerosus more commonly is seen in women, and the disease can present at any age, with a bimodal onset in prepubertal children and in postmenopausal women and men in the fourth decade of life.^1-3 A PubMed search of articles indexed for MEDLINE using the terms lichen and eyelid and manually screened revealed 6 cases of lichen sclerosus involving the eyelid.^2-4 We describe a case of lichen sclerosus involving the eyelid and its histopathology.

A 45-year-old woman was referred to dermatology for evaluation of a right lower eyelid lesion of 3 months’ duration. She first noted a small white patch under the eyelid that had doubled in size and felt firm without bleeding or ulceration. Her medical history was unremarkable, and there was no history of ophthalmic conditions, autoimmune disease, trauma, or cancer. An ophthalmic examination was normal, except for a 20×8-mm, flat, depigmented, firm papule with scalloped borders involving the right lower eyelid margin and extending inferiorly without evidence of madarosis or ulceration (Figure 1). She underwent an incisional biopsy that revealed the diagnosis of lichen sclerosus et atrophicus (Figure 2). A full dermatologic evaluation included a genital examination and did not reveal any additional lesions. Tacrolimus ointment was started to avoid the need for long-term use of periocular steroids and their complications.

Histopathology is useful to distinguish among these entities. Although there are no specific features separating lichen sclerosus from a morphea overlap and both entities often are classified by clinical presentation, lichen sclerosus demonstrates epidermal atrophy, follicular plugging, homogenized collagen in the upper dermis with dermal edema, and lichenoid lymphocytic infiltrate (Figure 2).¹ Extragenital lesions in particular also have been noted to have more epidermal atrophy and decreased rete ridges.²

To the Editor:

Lichen sclerosus is a chronic inflammatory skin disease of unknown cause that predominantly affects the anogenital region, but isolated extragenital lesions occur in 6% to 15% of patients. The buttocks, thighs, neck, shoulder, upper torso, and wrists most commonly are involved; the face rarely is affected.^1,2 Although the etiology of lichen sclerosus remains undetermined, there is growing evidence that autoimmunity may play a role.¹ Lichen sclerosus more commonly is seen in women, and the disease can present at any age, with a bimodal onset in prepubertal children and in postmenopausal women and men in the fourth decade of life.^1-3 A PubMed search of articles indexed for MEDLINE using the terms lichen and eyelid and manually screened revealed 6 cases of lichen sclerosus involving the eyelid.^2-4 We describe a case of lichen sclerosus involving the eyelid and its histopathology.

A 45-year-old woman was referred to dermatology for evaluation of a right lower eyelid lesion of 3 months’ duration. She first noted a small white patch under the eyelid that had doubled in size and felt firm without bleeding or ulceration. Her medical history was unremarkable, and there was no history of ophthalmic conditions, autoimmune disease, trauma, or cancer. An ophthalmic examination was normal, except for a 20×8-mm, flat, depigmented, firm papule with scalloped borders involving the right lower eyelid margin and extending inferiorly without evidence of madarosis or ulceration (Figure 1). She underwent an incisional biopsy that revealed the diagnosis of lichen sclerosus et atrophicus (Figure 2). A full dermatologic evaluation included a genital examination and did not reveal any additional lesions. Tacrolimus ointment was started to avoid the need for long-term use of periocular steroids and their complications.

Histopathology is useful to distinguish among these entities. Although there are no specific features separating lichen sclerosus from a morphea overlap and both entities often are classified by clinical presentation, lichen sclerosus demonstrates epidermal atrophy, follicular plugging, homogenized collagen in the upper dermis with dermal edema, and lichenoid lymphocytic infiltrate (Figure 2).¹ Extragenital lesions in particular also have been noted to have more epidermal atrophy and decreased rete ridges.²

The Diagnosis: Clonal Melanoacanthoma 

Melanoacanthoma (MA) is an extremely rare, benign, epidermal tumor histologically characterized by keratinocytes and large, pigmented, dendritic melanocytes. These lesions are loosely related to seborrheic keratoses, and the term was first coined by Mishima and Pinkus¹ in 1960. It is estimated that the lesion occurs in only 5 of 500,000 individuals and tends to occur in older, light-skinned individuals.² The majority are slow growing and are present on the head, neck, or upper extremities; however, similar lesions also have been reported on the oral mucosa.³ Melanoacanthomas range in size from 2×2 to 15×15 cm; are clinically pigmented; and present as either a papule, plaque, nodule, or horn.² 

Classic histologic findings of MA include papillomatosis, acanthosis, and hyperkeratosis with heavily pigmented dendritic melanocytes diffusely dispersed throughout all layers of the seborrheic keratosis-like epidermis.³ Other features include keratin-filled pseudocysts, Langerhans cells, reactive spindling of keratinocytes, and an inflammatory infiltrate. In our case, the classic histologic findings also were architecturally arranged in oval to round clones within the epidermis (quiz images 1 and 2). A MART-1 (melanoma antigen recognized by T cells) immunostain was obtained that highlighted the numerous but benign-appearing, dendritic melanocytes (quiz image 2 [inset]). A dual MART-1/Ki67 immunostain later was obtained and demonstrated a negligible proliferation index within the dendritic melanocytes. Therefore, the diagnosis of clonal MA was rendered. This formation of epidermal clones also is called the Borst-Jadassohn phenomenon, which rarely occurs in MAs. This subtype is important to recognize because the clonal pattern can more closely mimic malignant neoplasms such as melanoma.  

Hidroacanthoma simplex is an intraepidermal variant of eccrine poroma. It is a rare entity that typically occurs in the extremities of women as a hyperkeratotic plaque. These typically clonal epidermal tumors may be heavily pigmented and rarely contain dendritic melanocytes; therefore, they may be confused with MA. However, classic histology will reveal an intraepidermal clonal proliferation of bland, monotonous, cuboidal cells with ample pink cytoplasm, as well as occasional cuticle-lined ducts (Figure 1).⁴ These ducts will highlight with carcinoembryonic antigen and epithelial membrane antigen immunostaining.  

Malignant melanoma typically presents as a growing pigmented lesion and therefore can clinically mimic MA. Histologically, MA could be confused with melanoma due to the increased number of melanocytes plus the appearance of pagetoid spread resulting from the diffuse presence of melanocytes throughout the neoplasm. However, histologic assessment of melanoma should reveal cytologic atypia such as nuclear enlargement, hyperchromasia, molding, pleomorphism, and mitotic activity (Figure 2). Architectural atypia such as poor lateral circumscription of melanocytes, confluence and pagetoid spread of nondendritic atypical junctional melanocytes, production of pigment in deep dermal nests of melanocytes, and lack of maturation and dispersion of dermal melanocytes also should be seen.⁵ Unlike a melanocytic neoplasm, true melanocytic nests are not seen in MA, and the melanocytes are bland, normal-appearing but heavily pigmented, dendritic melanocytes. Electron microscopy has shown a defect in the transfer of melanin from these highly dendritic melanocytes to the keratinocytes.⁶  

Similar to melanoma, seborrheic keratosis presents as a pigmented growing lesion; therefore, definitive diagnosis often is achieved via skin biopsy. Classic histologic findings include acanthotic or exophytic epidermal growth with a dome-shaped configuration containing multiple cornified hornlike cysts (Figure 3).⁷ Multiple keratin plugs and variably sized concentric keratin islands are common features. There may be varying degrees of melanin pigment deposition among the proliferating cells, and clonal formation may occur. Melanocyte-specific special stains and immunostains can be used to differentiate MA from seborrheic keratosis by highlighting numerous dendritic melanocytes diffusely spread throughout the epidermis in MA vs a normal distribution of occasional junctional melanocytes in seborrheic keratosis.^2,8  

Squamous cell carcinoma in situ presents histologically with cytologically atypical keratinocytes encompassing the full thickness of the epidermis and sometimes crushing the basement membrane zone (Figure 4). There is a loss of the granular layer and overlying parakeratosis that often spares the adnexal ostial epithelium.⁹ Clonal formation can occur as well as increased pigment production. In comparison, bland keratinocytes are seen in MA.  

Establishing the diagnosis of MA based on clinical features alone can be difficult. Dermoscopy can prove to be useful and typically will show a sunburst pattern with ridges and fissures.² However, seborrheic keratoses and melanomas can have similar dermoscopic findings¹⁰; therefore, a biopsy often is necessary to establish the diagnosis. 

The Diagnosis: Clonal Melanoacanthoma 

Melanoacanthoma (MA) is an extremely rare, benign, epidermal tumor histologically characterized by keratinocytes and large, pigmented, dendritic melanocytes. These lesions are loosely related to seborrheic keratoses, and the term was first coined by Mishima and Pinkus¹ in 1960. It is estimated that the lesion occurs in only 5 of 500,000 individuals and tends to occur in older, light-skinned individuals.² The majority are slow growing and are present on the head, neck, or upper extremities; however, similar lesions also have been reported on the oral mucosa.³ Melanoacanthomas range in size from 2×2 to 15×15 cm; are clinically pigmented; and present as either a papule, plaque, nodule, or horn.² 

Classic histologic findings of MA include papillomatosis, acanthosis, and hyperkeratosis with heavily pigmented dendritic melanocytes diffusely dispersed throughout all layers of the seborrheic keratosis-like epidermis.³ Other features include keratin-filled pseudocysts, Langerhans cells, reactive spindling of keratinocytes, and an inflammatory infiltrate. In our case, the classic histologic findings also were architecturally arranged in oval to round clones within the epidermis (quiz images 1 and 2). A MART-1 (melanoma antigen recognized by T cells) immunostain was obtained that highlighted the numerous but benign-appearing, dendritic melanocytes (quiz image 2 [inset]). A dual MART-1/Ki67 immunostain later was obtained and demonstrated a negligible proliferation index within the dendritic melanocytes. Therefore, the diagnosis of clonal MA was rendered. This formation of epidermal clones also is called the Borst-Jadassohn phenomenon, which rarely occurs in MAs. This subtype is important to recognize because the clonal pattern can more closely mimic malignant neoplasms such as melanoma.  

Hidroacanthoma simplex is an intraepidermal variant of eccrine poroma. It is a rare entity that typically occurs in the extremities of women as a hyperkeratotic plaque. These typically clonal epidermal tumors may be heavily pigmented and rarely contain dendritic melanocytes; therefore, they may be confused with MA. However, classic histology will reveal an intraepidermal clonal proliferation of bland, monotonous, cuboidal cells with ample pink cytoplasm, as well as occasional cuticle-lined ducts (Figure 1).⁴ These ducts will highlight with carcinoembryonic antigen and epithelial membrane antigen immunostaining.  

Malignant melanoma typically presents as a growing pigmented lesion and therefore can clinically mimic MA. Histologically, MA could be confused with melanoma due to the increased number of melanocytes plus the appearance of pagetoid spread resulting from the diffuse presence of melanocytes throughout the neoplasm. However, histologic assessment of melanoma should reveal cytologic atypia such as nuclear enlargement, hyperchromasia, molding, pleomorphism, and mitotic activity (Figure 2). Architectural atypia such as poor lateral circumscription of melanocytes, confluence and pagetoid spread of nondendritic atypical junctional melanocytes, production of pigment in deep dermal nests of melanocytes, and lack of maturation and dispersion of dermal melanocytes also should be seen.⁵ Unlike a melanocytic neoplasm, true melanocytic nests are not seen in MA, and the melanocytes are bland, normal-appearing but heavily pigmented, dendritic melanocytes. Electron microscopy has shown a defect in the transfer of melanin from these highly dendritic melanocytes to the keratinocytes.⁶  

Similar to melanoma, seborrheic keratosis presents as a pigmented growing lesion; therefore, definitive diagnosis often is achieved via skin biopsy. Classic histologic findings include acanthotic or exophytic epidermal growth with a dome-shaped configuration containing multiple cornified hornlike cysts (Figure 3).⁷ Multiple keratin plugs and variably sized concentric keratin islands are common features. There may be varying degrees of melanin pigment deposition among the proliferating cells, and clonal formation may occur. Melanocyte-specific special stains and immunostains can be used to differentiate MA from seborrheic keratosis by highlighting numerous dendritic melanocytes diffusely spread throughout the epidermis in MA vs a normal distribution of occasional junctional melanocytes in seborrheic keratosis.^2,8  

Squamous cell carcinoma in situ presents histologically with cytologically atypical keratinocytes encompassing the full thickness of the epidermis and sometimes crushing the basement membrane zone (Figure 4). There is a loss of the granular layer and overlying parakeratosis that often spares the adnexal ostial epithelium.⁹ Clonal formation can occur as well as increased pigment production. In comparison, bland keratinocytes are seen in MA.  

Establishing the diagnosis of MA based on clinical features alone can be difficult. Dermoscopy can prove to be useful and typically will show a sunburst pattern with ridges and fissures.² However, seborrheic keratoses and melanomas can have similar dermoscopic findings¹⁰; therefore, a biopsy often is necessary to establish the diagnosis. 

The Diagnosis: Clonal Melanoacanthoma 

Melanoacanthoma (MA) is an extremely rare, benign, epidermal tumor histologically characterized by keratinocytes and large, pigmented, dendritic melanocytes. These lesions are loosely related to seborrheic keratoses, and the term was first coined by Mishima and Pinkus¹ in 1960. It is estimated that the lesion occurs in only 5 of 500,000 individuals and tends to occur in older, light-skinned individuals.² The majority are slow growing and are present on the head, neck, or upper extremities; however, similar lesions also have been reported on the oral mucosa.³ Melanoacanthomas range in size from 2×2 to 15×15 cm; are clinically pigmented; and present as either a papule, plaque, nodule, or horn.² 

Classic histologic findings of MA include papillomatosis, acanthosis, and hyperkeratosis with heavily pigmented dendritic melanocytes diffusely dispersed throughout all layers of the seborrheic keratosis-like epidermis.³ Other features include keratin-filled pseudocysts, Langerhans cells, reactive spindling of keratinocytes, and an inflammatory infiltrate. In our case, the classic histologic findings also were architecturally arranged in oval to round clones within the epidermis (quiz images 1 and 2). A MART-1 (melanoma antigen recognized by T cells) immunostain was obtained that highlighted the numerous but benign-appearing, dendritic melanocytes (quiz image 2 [inset]). A dual MART-1/Ki67 immunostain later was obtained and demonstrated a negligible proliferation index within the dendritic melanocytes. Therefore, the diagnosis of clonal MA was rendered. This formation of epidermal clones also is called the Borst-Jadassohn phenomenon, which rarely occurs in MAs. This subtype is important to recognize because the clonal pattern can more closely mimic malignant neoplasms such as melanoma.  

Hidroacanthoma simplex is an intraepidermal variant of eccrine poroma. It is a rare entity that typically occurs in the extremities of women as a hyperkeratotic plaque. These typically clonal epidermal tumors may be heavily pigmented and rarely contain dendritic melanocytes; therefore, they may be confused with MA. However, classic histology will reveal an intraepidermal clonal proliferation of bland, monotonous, cuboidal cells with ample pink cytoplasm, as well as occasional cuticle-lined ducts (Figure 1).⁴ These ducts will highlight with carcinoembryonic antigen and epithelial membrane antigen immunostaining.  

Malignant melanoma typically presents as a growing pigmented lesion and therefore can clinically mimic MA. Histologically, MA could be confused with melanoma due to the increased number of melanocytes plus the appearance of pagetoid spread resulting from the diffuse presence of melanocytes throughout the neoplasm. However, histologic assessment of melanoma should reveal cytologic atypia such as nuclear enlargement, hyperchromasia, molding, pleomorphism, and mitotic activity (Figure 2). Architectural atypia such as poor lateral circumscription of melanocytes, confluence and pagetoid spread of nondendritic atypical junctional melanocytes, production of pigment in deep dermal nests of melanocytes, and lack of maturation and dispersion of dermal melanocytes also should be seen.⁵ Unlike a melanocytic neoplasm, true melanocytic nests are not seen in MA, and the melanocytes are bland, normal-appearing but heavily pigmented, dendritic melanocytes. Electron microscopy has shown a defect in the transfer of melanin from these highly dendritic melanocytes to the keratinocytes.⁶  

Similar to melanoma, seborrheic keratosis presents as a pigmented growing lesion; therefore, definitive diagnosis often is achieved via skin biopsy. Classic histologic findings include acanthotic or exophytic epidermal growth with a dome-shaped configuration containing multiple cornified hornlike cysts (Figure 3).⁷ Multiple keratin plugs and variably sized concentric keratin islands are common features. There may be varying degrees of melanin pigment deposition among the proliferating cells, and clonal formation may occur. Melanocyte-specific special stains and immunostains can be used to differentiate MA from seborrheic keratosis by highlighting numerous dendritic melanocytes diffusely spread throughout the epidermis in MA vs a normal distribution of occasional junctional melanocytes in seborrheic keratosis.^2,8  

Squamous cell carcinoma in situ presents histologically with cytologically atypical keratinocytes encompassing the full thickness of the epidermis and sometimes crushing the basement membrane zone (Figure 4). There is a loss of the granular layer and overlying parakeratosis that often spares the adnexal ostial epithelium.⁹ Clonal formation can occur as well as increased pigment production. In comparison, bland keratinocytes are seen in MA.  

Establishing the diagnosis of MA based on clinical features alone can be difficult. Dermoscopy can prove to be useful and typically will show a sunburst pattern with ridges and fissures.² However, seborrheic keratoses and melanomas can have similar dermoscopic findings¹⁰; therefore, a biopsy often is necessary to establish the diagnosis.