Dermatopathology

To the Editor:

Erosive lichen planus (LP) often is painful, debilitating, and resistant to topical therapy making it both a diagnostic and therapeutic challenge. We report the case of an elderly woman with isolated perianal erosive LP, a rare clinical manifestation. We also review cases of erosive perianal LP reported in the literature.

A 72-year-old woman was referred to our dermatology clinic for evaluation of multiple pruritic and painful perianal lesions of 1 year’s duration. The lesions had remained stable since onset, with no other reported lesions elsewhere on body, including the mucosae. Her medical history was notable for rheumatoid arthritis, osteoporosis, hypercholesterolemia, and hypertension. She was taking methotrexate, folic acid, abatacept, alendronate, atorvastatin, and lisinopril. The patient reported she had been using abatacept for 3 years and lisinopril for 2 years. Her primary care physician initially treated the lesions as hemorrhoids but referred her to a gastroenterologist when they failed to improve. Gastroenterology evaluated the patient, and a colonoscopy was performed with unremarkable results. Thus, she was referred to dermatology for further evaluation.

Physical examination revealed 2 tender, sharply defined, angulated erosions with irregular violaceous borders involving the perianal skin (Figure 1). A biopsy of one of the lesions was taken. Histopathologic examination revealed acanthosis of the epidermis with slight compact hyperkeratosis, scattered dyskeratotic keratinocytes, and a dense bandlike lymphohistiocytic infiltrate that obliterated the dermoepidermal junction (Figure 2). A diagnosis of perianal erosive LP was made. The patient was prescribed mometasone ointment 0.1% daily with notable improvement after 2 months.

Treatment of LP varies depending on the location and subtype of the lesions and is primarily aimed at improving symptoms. Topical corticosteroids are the standard treatment of LP; however, there is limited evidence regarding their efficacy for mucosal LP. Although randomized controlled trials assessing the efficacy of different interventions on oral erosive LP are available in the literature,¹⁵ there is a paucity of studies addressing this topic for genital or perianal LP. A review of the literature regarding perianal erosive LP suggests good response to high-potency topical steroids and calcineurin inhibitors with resolution of lesions within 3 to 4 weeks.^11,15-18

Erosive LP is a painful variant that can cause erosions, ulcerations, and scarring. It rarely is seen in the perianal region alone and presents a diagnostic challenge. Treatment with high-potency topical steroid therapy seems to be effective in the few cases that have been reported as well as in our case. More comprehensive data from randomized controlled trials would be needed to evaluate their efficacy compared to other therapies.

To the Editor:

Erosive lichen planus (LP) often is painful, debilitating, and resistant to topical therapy making it both a diagnostic and therapeutic challenge. We report the case of an elderly woman with isolated perianal erosive LP, a rare clinical manifestation. We also review cases of erosive perianal LP reported in the literature.

A 72-year-old woman was referred to our dermatology clinic for evaluation of multiple pruritic and painful perianal lesions of 1 year’s duration. The lesions had remained stable since onset, with no other reported lesions elsewhere on body, including the mucosae. Her medical history was notable for rheumatoid arthritis, osteoporosis, hypercholesterolemia, and hypertension. She was taking methotrexate, folic acid, abatacept, alendronate, atorvastatin, and lisinopril. The patient reported she had been using abatacept for 3 years and lisinopril for 2 years. Her primary care physician initially treated the lesions as hemorrhoids but referred her to a gastroenterologist when they failed to improve. Gastroenterology evaluated the patient, and a colonoscopy was performed with unremarkable results. Thus, she was referred to dermatology for further evaluation.

Physical examination revealed 2 tender, sharply defined, angulated erosions with irregular violaceous borders involving the perianal skin (Figure 1). A biopsy of one of the lesions was taken. Histopathologic examination revealed acanthosis of the epidermis with slight compact hyperkeratosis, scattered dyskeratotic keratinocytes, and a dense bandlike lymphohistiocytic infiltrate that obliterated the dermoepidermal junction (Figure 2). A diagnosis of perianal erosive LP was made. The patient was prescribed mometasone ointment 0.1% daily with notable improvement after 2 months.

Treatment of LP varies depending on the location and subtype of the lesions and is primarily aimed at improving symptoms. Topical corticosteroids are the standard treatment of LP; however, there is limited evidence regarding their efficacy for mucosal LP. Although randomized controlled trials assessing the efficacy of different interventions on oral erosive LP are available in the literature,¹⁵ there is a paucity of studies addressing this topic for genital or perianal LP. A review of the literature regarding perianal erosive LP suggests good response to high-potency topical steroids and calcineurin inhibitors with resolution of lesions within 3 to 4 weeks.^11,15-18

Erosive LP is a painful variant that can cause erosions, ulcerations, and scarring. It rarely is seen in the perianal region alone and presents a diagnostic challenge. Treatment with high-potency topical steroid therapy seems to be effective in the few cases that have been reported as well as in our case. More comprehensive data from randomized controlled trials would be needed to evaluate their efficacy compared to other therapies.

To the Editor:

Erosive lichen planus (LP) often is painful, debilitating, and resistant to topical therapy making it both a diagnostic and therapeutic challenge. We report the case of an elderly woman with isolated perianal erosive LP, a rare clinical manifestation. We also review cases of erosive perianal LP reported in the literature.

A 72-year-old woman was referred to our dermatology clinic for evaluation of multiple pruritic and painful perianal lesions of 1 year’s duration. The lesions had remained stable since onset, with no other reported lesions elsewhere on body, including the mucosae. Her medical history was notable for rheumatoid arthritis, osteoporosis, hypercholesterolemia, and hypertension. She was taking methotrexate, folic acid, abatacept, alendronate, atorvastatin, and lisinopril. The patient reported she had been using abatacept for 3 years and lisinopril for 2 years. Her primary care physician initially treated the lesions as hemorrhoids but referred her to a gastroenterologist when they failed to improve. Gastroenterology evaluated the patient, and a colonoscopy was performed with unremarkable results. Thus, she was referred to dermatology for further evaluation.

Physical examination revealed 2 tender, sharply defined, angulated erosions with irregular violaceous borders involving the perianal skin (Figure 1). A biopsy of one of the lesions was taken. Histopathologic examination revealed acanthosis of the epidermis with slight compact hyperkeratosis, scattered dyskeratotic keratinocytes, and a dense bandlike lymphohistiocytic infiltrate that obliterated the dermoepidermal junction (Figure 2). A diagnosis of perianal erosive LP was made. The patient was prescribed mometasone ointment 0.1% daily with notable improvement after 2 months.

Treatment of LP varies depending on the location and subtype of the lesions and is primarily aimed at improving symptoms. Topical corticosteroids are the standard treatment of LP; however, there is limited evidence regarding their efficacy for mucosal LP. Although randomized controlled trials assessing the efficacy of different interventions on oral erosive LP are available in the literature,¹⁵ there is a paucity of studies addressing this topic for genital or perianal LP. A review of the literature regarding perianal erosive LP suggests good response to high-potency topical steroids and calcineurin inhibitors with resolution of lesions within 3 to 4 weeks.^11,15-18

Erosive LP is a painful variant that can cause erosions, ulcerations, and scarring. It rarely is seen in the perianal region alone and presents a diagnostic challenge. Treatment with high-potency topical steroid therapy seems to be effective in the few cases that have been reported as well as in our case. More comprehensive data from randomized controlled trials would be needed to evaluate their efficacy compared to other therapies.

The Diagnosis: Lichen Planus Pigmentosus-Inversus 

Histopathologic examination revealed hyperkeratosis with dense, bandlike, lymphocytic inflammation at the dermoepidermal junction with associated melanin-containing macrophages in the papillary dermis (Figure 1). The physical examination and histopathology were consistent with a diagnosis of lichen planus pigmentosus-inversus (LPPI). Treatment was discussed with the patient, with options including phototherapy, tacrolimus, or a high-dose steroid. Given that the lesions were asymptomatic and not bothersome, the patient denied treatment and agreed to routine follow-up. 

Given the gender, age, and clinical features of our patient, this case represents a classic scenario of LPPI. It currently is unknown if ethnicity plays a role in the disorder. Lichen planus pigmentosus-inversus initially was thought to be more prevalent in White patients; however, studies have been reported in individuals with darker skin.^1,2 

The main differential diagnosis includes erythema dyschromicum perstans, postinflammatory hyperpigmentation, and lichen planus. Although erythema dyschromicum perstans develops in individuals with darker skin, lesions are restricted to the upper torso and limbs.^2-4 In both lichen planus and lichen actinicus, skin findings primarily develop in sun-exposed areas, such as the face, neck, and hands.^4,6 Given the negative history of trauma, postinflammatory hyperpigmentation was unlikely in our patient. Furthermore, a distinguishing characteristic of LPPI is the deposition of melanin deep within the dermal layer.³ 

Lesions developing in nonexposed intertriginous skin makes LPPI unique and distinguishes it from other more common conditions. The lesions commonly are hyperpigmented and are not as pruritic as other lichen-associated conditions. Lichen planus pigmentosus-inversus often persists for months, and the rash generally is resistant to treatment.^2,5 Topical tacrolimus and high-dose steroids may improve symptoms, though results have varied substantially. In addition, some cases have resolved spontaneously.^1,4,6,7 Because LPPI is asymptomatic and benign, spontaneous resolution and routine care is a reasonable treatment strategy. Some cases have supported this strategy as safe and high-value care.² 

The Diagnosis: Lichen Planus Pigmentosus-Inversus 

Histopathologic examination revealed hyperkeratosis with dense, bandlike, lymphocytic inflammation at the dermoepidermal junction with associated melanin-containing macrophages in the papillary dermis (Figure 1). The physical examination and histopathology were consistent with a diagnosis of lichen planus pigmentosus-inversus (LPPI). Treatment was discussed with the patient, with options including phototherapy, tacrolimus, or a high-dose steroid. Given that the lesions were asymptomatic and not bothersome, the patient denied treatment and agreed to routine follow-up. 

Given the gender, age, and clinical features of our patient, this case represents a classic scenario of LPPI. It currently is unknown if ethnicity plays a role in the disorder. Lichen planus pigmentosus-inversus initially was thought to be more prevalent in White patients; however, studies have been reported in individuals with darker skin.^1,2 

The main differential diagnosis includes erythema dyschromicum perstans, postinflammatory hyperpigmentation, and lichen planus. Although erythema dyschromicum perstans develops in individuals with darker skin, lesions are restricted to the upper torso and limbs.^2-4 In both lichen planus and lichen actinicus, skin findings primarily develop in sun-exposed areas, such as the face, neck, and hands.^4,6 Given the negative history of trauma, postinflammatory hyperpigmentation was unlikely in our patient. Furthermore, a distinguishing characteristic of LPPI is the deposition of melanin deep within the dermal layer.³ 

Lesions developing in nonexposed intertriginous skin makes LPPI unique and distinguishes it from other more common conditions. The lesions commonly are hyperpigmented and are not as pruritic as other lichen-associated conditions. Lichen planus pigmentosus-inversus often persists for months, and the rash generally is resistant to treatment.^2,5 Topical tacrolimus and high-dose steroids may improve symptoms, though results have varied substantially. In addition, some cases have resolved spontaneously.^1,4,6,7 Because LPPI is asymptomatic and benign, spontaneous resolution and routine care is a reasonable treatment strategy. Some cases have supported this strategy as safe and high-value care.² 

The Diagnosis: Lichen Planus Pigmentosus-Inversus 

Histopathologic examination revealed hyperkeratosis with dense, bandlike, lymphocytic inflammation at the dermoepidermal junction with associated melanin-containing macrophages in the papillary dermis (Figure 1). The physical examination and histopathology were consistent with a diagnosis of lichen planus pigmentosus-inversus (LPPI). Treatment was discussed with the patient, with options including phototherapy, tacrolimus, or a high-dose steroid. Given that the lesions were asymptomatic and not bothersome, the patient denied treatment and agreed to routine follow-up. 

Given the gender, age, and clinical features of our patient, this case represents a classic scenario of LPPI. It currently is unknown if ethnicity plays a role in the disorder. Lichen planus pigmentosus-inversus initially was thought to be more prevalent in White patients; however, studies have been reported in individuals with darker skin.^1,2 

The main differential diagnosis includes erythema dyschromicum perstans, postinflammatory hyperpigmentation, and lichen planus. Although erythema dyschromicum perstans develops in individuals with darker skin, lesions are restricted to the upper torso and limbs.^2-4 In both lichen planus and lichen actinicus, skin findings primarily develop in sun-exposed areas, such as the face, neck, and hands.^4,6 Given the negative history of trauma, postinflammatory hyperpigmentation was unlikely in our patient. Furthermore, a distinguishing characteristic of LPPI is the deposition of melanin deep within the dermal layer.³ 

Lesions developing in nonexposed intertriginous skin makes LPPI unique and distinguishes it from other more common conditions. The lesions commonly are hyperpigmented and are not as pruritic as other lichen-associated conditions. Lichen planus pigmentosus-inversus often persists for months, and the rash generally is resistant to treatment.^2,5 Topical tacrolimus and high-dose steroids may improve symptoms, though results have varied substantially. In addition, some cases have resolved spontaneously.^1,4,6,7 Because LPPI is asymptomatic and benign, spontaneous resolution and routine care is a reasonable treatment strategy. Some cases have supported this strategy as safe and high-value care.² 

To the Editor:

A 65-year-old man with severe atherosclerotic disease developed multiple painful eschars on the lower abdomen, thighs, sacrum, and perineum. He initially presented with myocardial ischemia and claudication and underwent 3 cardiac catheterizations as well as stenting of the superficial femoral artery. Within 2 weeks, he developed exquisitely tender nodules on the lower abdomen, clinically presumed to be sites of enoxaparin injections. These lesions gradually expanded and ulcerated to involve the sacrum, buttock, perineum, and upper thighs (Figure 1). Two punch biopsies from ulcerated skin taken 10 days apart demonstrated necrosis of skin and subcutaneous fat without evidence of vasculitis, vasculopathy, emboli, or notable inflammation despite examination of multiple levels of all submitted tissue. A definitive cause for the ulcerations remained elusive with development of new lesions. A third incisional biopsy of a newly developed, nonulcerated, subcutaneous nodule performed 8 weeks after presentation revealed multiple cholesterol emboli (Figure 2). He was treated with warfarin and clopidogrel bisulfate as well as local wound care. The lesions slowly resolved over the next 4 to 6 months.

Cholesterol embolization syndrome occurs when disrupted atherosclerotic plaques embolize from large proximal arteries to more distal arterioles, resulting in ischemic damage to 1 or more organ systems.¹ It can occur spontaneously but often is a consequence of thrombolytic therapy, anticoagulation, and angioinvasive procedures.^2,3 Cutaneous manifestations include livedo reticularis, retiform purpura, nodules, and gangrene. Although livedo reticularis may extend from the legs to the trunk, gangrenous lesions predominantly involve the distal digits.

This case illustrates the challenge in diagnosis of cholesterol emboli, both clinically and histologically. Cutaneous lesions are morphologically variable and often occur with systemic manifestations, mimicking numerous conditions.¹ Lower extremity involvement is a well-known occurrence in cholesterol embolization (ie, blue toe syndrome); however, periumbilical and lumbosacral lesions have not been emphasized in the dermatologic or peripheral vascular literature. Our patient’s initial diagnosis was enoxaparin necrosis at abdominal injection sites; however, this unusual distribution of lesions was ultimately determined to be the consequence of cholesterol embolization from the inferior epigastric and superficial external pudendal arteries at the time of stenting of the superficial femoral artery. Proximal truncal involvement should be recognized as an atypical but important cutaneous manifestation to facilitate timely diagnosis and treatment.^4,5

Our patient’s course also highlights the potential need for multiple biopsies. Although the gold standard for diagnosis is histologic confirmation, a negative biopsy does not always exclude cholesterol emboli, and one should have a low threshold to perform additional biopsies in the appropriate clinical setting.

To the Editor:

A 65-year-old man with severe atherosclerotic disease developed multiple painful eschars on the lower abdomen, thighs, sacrum, and perineum. He initially presented with myocardial ischemia and claudication and underwent 3 cardiac catheterizations as well as stenting of the superficial femoral artery. Within 2 weeks, he developed exquisitely tender nodules on the lower abdomen, clinically presumed to be sites of enoxaparin injections. These lesions gradually expanded and ulcerated to involve the sacrum, buttock, perineum, and upper thighs (Figure 1). Two punch biopsies from ulcerated skin taken 10 days apart demonstrated necrosis of skin and subcutaneous fat without evidence of vasculitis, vasculopathy, emboli, or notable inflammation despite examination of multiple levels of all submitted tissue. A definitive cause for the ulcerations remained elusive with development of new lesions. A third incisional biopsy of a newly developed, nonulcerated, subcutaneous nodule performed 8 weeks after presentation revealed multiple cholesterol emboli (Figure 2). He was treated with warfarin and clopidogrel bisulfate as well as local wound care. The lesions slowly resolved over the next 4 to 6 months.

Cholesterol embolization syndrome occurs when disrupted atherosclerotic plaques embolize from large proximal arteries to more distal arterioles, resulting in ischemic damage to 1 or more organ systems.¹ It can occur spontaneously but often is a consequence of thrombolytic therapy, anticoagulation, and angioinvasive procedures.^2,3 Cutaneous manifestations include livedo reticularis, retiform purpura, nodules, and gangrene. Although livedo reticularis may extend from the legs to the trunk, gangrenous lesions predominantly involve the distal digits.

This case illustrates the challenge in diagnosis of cholesterol emboli, both clinically and histologically. Cutaneous lesions are morphologically variable and often occur with systemic manifestations, mimicking numerous conditions.¹ Lower extremity involvement is a well-known occurrence in cholesterol embolization (ie, blue toe syndrome); however, periumbilical and lumbosacral lesions have not been emphasized in the dermatologic or peripheral vascular literature. Our patient’s initial diagnosis was enoxaparin necrosis at abdominal injection sites; however, this unusual distribution of lesions was ultimately determined to be the consequence of cholesterol embolization from the inferior epigastric and superficial external pudendal arteries at the time of stenting of the superficial femoral artery. Proximal truncal involvement should be recognized as an atypical but important cutaneous manifestation to facilitate timely diagnosis and treatment.^4,5

Our patient’s course also highlights the potential need for multiple biopsies. Although the gold standard for diagnosis is histologic confirmation, a negative biopsy does not always exclude cholesterol emboli, and one should have a low threshold to perform additional biopsies in the appropriate clinical setting.

To the Editor:

A 65-year-old man with severe atherosclerotic disease developed multiple painful eschars on the lower abdomen, thighs, sacrum, and perineum. He initially presented with myocardial ischemia and claudication and underwent 3 cardiac catheterizations as well as stenting of the superficial femoral artery. Within 2 weeks, he developed exquisitely tender nodules on the lower abdomen, clinically presumed to be sites of enoxaparin injections. These lesions gradually expanded and ulcerated to involve the sacrum, buttock, perineum, and upper thighs (Figure 1). Two punch biopsies from ulcerated skin taken 10 days apart demonstrated necrosis of skin and subcutaneous fat without evidence of vasculitis, vasculopathy, emboli, or notable inflammation despite examination of multiple levels of all submitted tissue. A definitive cause for the ulcerations remained elusive with development of new lesions. A third incisional biopsy of a newly developed, nonulcerated, subcutaneous nodule performed 8 weeks after presentation revealed multiple cholesterol emboli (Figure 2). He was treated with warfarin and clopidogrel bisulfate as well as local wound care. The lesions slowly resolved over the next 4 to 6 months.

Cholesterol embolization syndrome occurs when disrupted atherosclerotic plaques embolize from large proximal arteries to more distal arterioles, resulting in ischemic damage to 1 or more organ systems.¹ It can occur spontaneously but often is a consequence of thrombolytic therapy, anticoagulation, and angioinvasive procedures.^2,3 Cutaneous manifestations include livedo reticularis, retiform purpura, nodules, and gangrene. Although livedo reticularis may extend from the legs to the trunk, gangrenous lesions predominantly involve the distal digits.

This case illustrates the challenge in diagnosis of cholesterol emboli, both clinically and histologically. Cutaneous lesions are morphologically variable and often occur with systemic manifestations, mimicking numerous conditions.¹ Lower extremity involvement is a well-known occurrence in cholesterol embolization (ie, blue toe syndrome); however, periumbilical and lumbosacral lesions have not been emphasized in the dermatologic or peripheral vascular literature. Our patient’s initial diagnosis was enoxaparin necrosis at abdominal injection sites; however, this unusual distribution of lesions was ultimately determined to be the consequence of cholesterol embolization from the inferior epigastric and superficial external pudendal arteries at the time of stenting of the superficial femoral artery. Proximal truncal involvement should be recognized as an atypical but important cutaneous manifestation to facilitate timely diagnosis and treatment.^4,5

Our patient’s course also highlights the potential need for multiple biopsies. Although the gold standard for diagnosis is histologic confirmation, a negative biopsy does not always exclude cholesterol emboli, and one should have a low threshold to perform additional biopsies in the appropriate clinical setting.

The Diagnosis: Cutaneous Collagenous Vasculopathy 

Cutaneous collagenous vasculopathy (CCV) is an idiopathic microangiopathy of the small vessels in the superficial dermis. A condition first identified by Salama and Rosenthal¹ in 2000, CCV likely is underreported, as its clinical mimickers are not routinely biopsied.² It presents as asymptomatic telangiectatic macules, initially on the lower extremities and often spreading to the trunk. Cutaneous collagenous vasculopathy often is seen in middle-aged adults, and most patients have comorbidities such as hypertension, diabetes mellitus, or cardiovascular disease. The exact etiology of this disease is unknown.^3,4 

Histopathologically, CCV is characterized by dilated superficial vessels with thickened eosinophilic walls. The eosinophilic material is composed of hyalinized type IV collagen, which is periodic acid-Schiff positive and diastase resistant (Figure 1).^3,4 Stains for amyloid are negative.  

Generalized essential telangiectasia (GET) is a condition that presents with symmetric, blanchable, erythematous telangiectases.⁵ These lesions can occur alone or can accompany systemic diseases. Similar to CCV, the telangiectases tend to begin on the legs before gradually spreading to the trunk; however, this process more often is seen in females and occurs at an earlier age. Unlike CCV, GET can occur on mucosal surfaces, with cases of conjunctival and oral involvement reported.⁶ Generalized essential telangiectasia usually is a diagnosis of exclusion.^7,8 It is thought that many CCV lesions have been misclassified clinically as GET, which highlights the importance of biopsy. Microscopically, GET is distinct from CCV in that the superficial dermis lacks thick-walled vessels.^5,7 Although usually not associated with systemic diseases or progressive morbidity, treatment options are limited.⁸ 

Livedoid vasculopathy, also known as atrophie blanche, is caused by fibrin thrombi occlusion of dermal vessels. Clinically, patients have recurrent telangiectatic papules and painful ulcers on the lower extremities that gradually heal, leaving behind white stellate scars. It is caused by an underlying prothrombotic state with a superimposed inflammatory response.⁹ Livedoid vasculopathy primarily affects middle-aged women, and many patients have comorbidities such as scleroderma or systemic lupus erythematosus. Histologically, the epidermis often is ulcerated, and thrombi are visualized within small vessels. Eosinophilic fibrinoid material is deposited in vessel walls, including but not confined to vessels at the base of the epidermal ulcer (Figure 2). The fibrinoid material is periodic acid-Schiff positive and diastase resistant and can be highlighted with immunofluorescence, which may help to distinguish this entity from CCV.^1,9 As the disease progresses, vessels are diffusely hyalinized, and there is epidermal atrophy and dermal sclerosis. Treatment options include antiplatelet and fibrinolytic drugs with a multidisciplinary approach to resolve pain and scarring.⁹ 

Primary systemic amyloidosis is a rare condition, and cutaneous manifestations are seen in approximately one-third of affected individuals. Amyloid deposition results in waxy papules that predominantly affect the face and periorbital areas but also may occur on the neck, flexural areas, and genitalia.⁵ Because the amyloid deposits also can be found within vessel walls, hemorrhagic lesions may occur. Microscopically, amorphous eosinophilic material can be found within the vessel walls, similar to CCV (Figure 3A); however, when stained with Congo red, cutaneous amyloidosis shows waxy red-orange material involving the vessel walls and exhibits apple green birefringence under polarization (Figure 3B).¹⁰ Amyloid also will be negative for type IV collagen, fibronectin, and laminin, whereas CCV will be positive.⁵

The Diagnosis: Cutaneous Collagenous Vasculopathy 

Cutaneous collagenous vasculopathy (CCV) is an idiopathic microangiopathy of the small vessels in the superficial dermis. A condition first identified by Salama and Rosenthal¹ in 2000, CCV likely is underreported, as its clinical mimickers are not routinely biopsied.² It presents as asymptomatic telangiectatic macules, initially on the lower extremities and often spreading to the trunk. Cutaneous collagenous vasculopathy often is seen in middle-aged adults, and most patients have comorbidities such as hypertension, diabetes mellitus, or cardiovascular disease. The exact etiology of this disease is unknown.^3,4 

Histopathologically, CCV is characterized by dilated superficial vessels with thickened eosinophilic walls. The eosinophilic material is composed of hyalinized type IV collagen, which is periodic acid-Schiff positive and diastase resistant (Figure 1).^3,4 Stains for amyloid are negative.  

Generalized essential telangiectasia (GET) is a condition that presents with symmetric, blanchable, erythematous telangiectases.⁵ These lesions can occur alone or can accompany systemic diseases. Similar to CCV, the telangiectases tend to begin on the legs before gradually spreading to the trunk; however, this process more often is seen in females and occurs at an earlier age. Unlike CCV, GET can occur on mucosal surfaces, with cases of conjunctival and oral involvement reported.⁶ Generalized essential telangiectasia usually is a diagnosis of exclusion.^7,8 It is thought that many CCV lesions have been misclassified clinically as GET, which highlights the importance of biopsy. Microscopically, GET is distinct from CCV in that the superficial dermis lacks thick-walled vessels.^5,7 Although usually not associated with systemic diseases or progressive morbidity, treatment options are limited.⁸ 

Livedoid vasculopathy, also known as atrophie blanche, is caused by fibrin thrombi occlusion of dermal vessels. Clinically, patients have recurrent telangiectatic papules and painful ulcers on the lower extremities that gradually heal, leaving behind white stellate scars. It is caused by an underlying prothrombotic state with a superimposed inflammatory response.⁹ Livedoid vasculopathy primarily affects middle-aged women, and many patients have comorbidities such as scleroderma or systemic lupus erythematosus. Histologically, the epidermis often is ulcerated, and thrombi are visualized within small vessels. Eosinophilic fibrinoid material is deposited in vessel walls, including but not confined to vessels at the base of the epidermal ulcer (Figure 2). The fibrinoid material is periodic acid-Schiff positive and diastase resistant and can be highlighted with immunofluorescence, which may help to distinguish this entity from CCV.^1,9 As the disease progresses, vessels are diffusely hyalinized, and there is epidermal atrophy and dermal sclerosis. Treatment options include antiplatelet and fibrinolytic drugs with a multidisciplinary approach to resolve pain and scarring.⁹ 

Primary systemic amyloidosis is a rare condition, and cutaneous manifestations are seen in approximately one-third of affected individuals. Amyloid deposition results in waxy papules that predominantly affect the face and periorbital areas but also may occur on the neck, flexural areas, and genitalia.⁵ Because the amyloid deposits also can be found within vessel walls, hemorrhagic lesions may occur. Microscopically, amorphous eosinophilic material can be found within the vessel walls, similar to CCV (Figure 3A); however, when stained with Congo red, cutaneous amyloidosis shows waxy red-orange material involving the vessel walls and exhibits apple green birefringence under polarization (Figure 3B).¹⁰ Amyloid also will be negative for type IV collagen, fibronectin, and laminin, whereas CCV will be positive.⁵

The Diagnosis: Cutaneous Collagenous Vasculopathy 

Cutaneous collagenous vasculopathy (CCV) is an idiopathic microangiopathy of the small vessels in the superficial dermis. A condition first identified by Salama and Rosenthal¹ in 2000, CCV likely is underreported, as its clinical mimickers are not routinely biopsied.² It presents as asymptomatic telangiectatic macules, initially on the lower extremities and often spreading to the trunk. Cutaneous collagenous vasculopathy often is seen in middle-aged adults, and most patients have comorbidities such as hypertension, diabetes mellitus, or cardiovascular disease. The exact etiology of this disease is unknown.^3,4 

Histopathologically, CCV is characterized by dilated superficial vessels with thickened eosinophilic walls. The eosinophilic material is composed of hyalinized type IV collagen, which is periodic acid-Schiff positive and diastase resistant (Figure 1).^3,4 Stains for amyloid are negative.  

Generalized essential telangiectasia (GET) is a condition that presents with symmetric, blanchable, erythematous telangiectases.⁵ These lesions can occur alone or can accompany systemic diseases. Similar to CCV, the telangiectases tend to begin on the legs before gradually spreading to the trunk; however, this process more often is seen in females and occurs at an earlier age. Unlike CCV, GET can occur on mucosal surfaces, with cases of conjunctival and oral involvement reported.⁶ Generalized essential telangiectasia usually is a diagnosis of exclusion.^7,8 It is thought that many CCV lesions have been misclassified clinically as GET, which highlights the importance of biopsy. Microscopically, GET is distinct from CCV in that the superficial dermis lacks thick-walled vessels.^5,7 Although usually not associated with systemic diseases or progressive morbidity, treatment options are limited.⁸ 

Livedoid vasculopathy, also known as atrophie blanche, is caused by fibrin thrombi occlusion of dermal vessels. Clinically, patients have recurrent telangiectatic papules and painful ulcers on the lower extremities that gradually heal, leaving behind white stellate scars. It is caused by an underlying prothrombotic state with a superimposed inflammatory response.⁹ Livedoid vasculopathy primarily affects middle-aged women, and many patients have comorbidities such as scleroderma or systemic lupus erythematosus. Histologically, the epidermis often is ulcerated, and thrombi are visualized within small vessels. Eosinophilic fibrinoid material is deposited in vessel walls, including but not confined to vessels at the base of the epidermal ulcer (Figure 2). The fibrinoid material is periodic acid-Schiff positive and diastase resistant and can be highlighted with immunofluorescence, which may help to distinguish this entity from CCV.^1,9 As the disease progresses, vessels are diffusely hyalinized, and there is epidermal atrophy and dermal sclerosis. Treatment options include antiplatelet and fibrinolytic drugs with a multidisciplinary approach to resolve pain and scarring.⁹ 

Primary systemic amyloidosis is a rare condition, and cutaneous manifestations are seen in approximately one-third of affected individuals. Amyloid deposition results in waxy papules that predominantly affect the face and periorbital areas but also may occur on the neck, flexural areas, and genitalia.⁵ Because the amyloid deposits also can be found within vessel walls, hemorrhagic lesions may occur. Microscopically, amorphous eosinophilic material can be found within the vessel walls, similar to CCV (Figure 3A); however, when stained with Congo red, cutaneous amyloidosis shows waxy red-orange material involving the vessel walls and exhibits apple green birefringence under polarization (Figure 3B).¹⁰ Amyloid also will be negative for type IV collagen, fibronectin, and laminin, whereas CCV will be positive.⁵

In 2019, the   2 Current Procedural Terminology (CPT) codes for skin biopsies (11100 and 11101) were replaced with 6 new CPT codes that   specify biopsy technique   and associated procedural complexity. ^1,2 Prior to the coding changes, all biopsies were reimbursed at the same payment level, but a punch biopsy (11104; national nonfacility Medicare payment, $133.29) is now reimbursed more than a shave biopsy (11102; national nonfacility Medicare payment, $106.42). ³ We sought to evaluate whether the decrease in reimbursement for shave biopsies and concurrent increase in reimbursement for punch biopsies led to a shift from shave to punch biopsy utilization.

Methods

We examined shave and punch biopsies submitted for pathologic examination at Brigham and Women’s Hospital, Massachusetts General Hospital, and Massachusetts General Physician’s Organization (all in Boston, Massachusetts), and Penn Medicine, University of Pennsylvania Health System (Philadelphia, Pennsylvania), in May 2018 vs May 2019 (four months after new codes were implemented). This study was approved by Partners HealthCare (Boston, Massachusetts) and the University of Pennsylvania institutional review boards.

We included shave and punch biopsies of skin performed by physician dermatologists and mid-level providers (ie, physician assistants, nurse practitioners) at dermatology practices. All biopsies performed by a technique other than shave or punch, unspecified biopsy type, consultation cases, nonskin biopsies (eg, mucosa), and biopsies performed at nondermatology practices were excluded. We also excluded biopsies by providers who were not present during both study periods to account for provider mix.

Statistical Analysis
To evaluate for changes in the ratio of shave to punch biopsy utilization over time, we performed χ² tests. Because care practices may differ between private and academic settings as well as between physicians and mid-level providers, we performed subgroup analyses by practice setting and provider type.⁴

Results

We identified 11,785 biopsies (12.11% of which were punch) submitted for pathologic examination in May 2018 compared to 11,291 biopsies (12.08% of which were punch) in May 2019 (Table). The overall use of punch biopsies relative to shave biopsies did not change between the years. There was a relative decrease in punch biopsy use among academic practices (−1.88%; P=.032) and a relative increase in punch biopsy use among private practices (+0.90%; P=.043). Provider type was not associated with differing utilization of biopsy type.

Comment

Overall, there was not a considerable shift in utilization behavior from shave to punch biopsies after the introduction of new coding changes. However, our study does demonstrate a small yet significant increase in punch biopsy utilization among private practices, and a decrease among academic practices. Although the change in biopsy utilization behavior is small in magnitude, it may have a substantial impact when extrapolated to behavior across the entire United States.

We were unable to assess additional factors, such as clinical diagnosis, body site, and cosmetic concerns, that may impact biopsy type selection in this study. Although we included multiple study sites to improve generalizability, our findings may not be representative of all biopsies performed in the dermatology setting. The baseline difference in relative punch biopsy use in academic vs private practices may reflect differences in patient populations and chief concerns, but assuming these features are stable over a 1-year time period, our findings should remain valid. Future studies should focus on qualitative evaluations of physician decision-making and evaluate whether similar trends persist over time.

Conclusion

Skin biopsy utilization trends among differing practice and provider types should continue to be monitored to assess for longitudinal trends in utilization within the context of updated billing codes and associated reimbursements.

In 2019, the   2 Current Procedural Terminology (CPT) codes for skin biopsies (11100 and 11101) were replaced with 6 new CPT codes that   specify biopsy technique   and associated procedural complexity. ^1,2 Prior to the coding changes, all biopsies were reimbursed at the same payment level, but a punch biopsy (11104; national nonfacility Medicare payment, $133.29) is now reimbursed more than a shave biopsy (11102; national nonfacility Medicare payment, $106.42). ³ We sought to evaluate whether the decrease in reimbursement for shave biopsies and concurrent increase in reimbursement for punch biopsies led to a shift from shave to punch biopsy utilization.

Methods

We examined shave and punch biopsies submitted for pathologic examination at Brigham and Women’s Hospital, Massachusetts General Hospital, and Massachusetts General Physician’s Organization (all in Boston, Massachusetts), and Penn Medicine, University of Pennsylvania Health System (Philadelphia, Pennsylvania), in May 2018 vs May 2019 (four months after new codes were implemented). This study was approved by Partners HealthCare (Boston, Massachusetts) and the University of Pennsylvania institutional review boards.

We included shave and punch biopsies of skin performed by physician dermatologists and mid-level providers (ie, physician assistants, nurse practitioners) at dermatology practices. All biopsies performed by a technique other than shave or punch, unspecified biopsy type, consultation cases, nonskin biopsies (eg, mucosa), and biopsies performed at nondermatology practices were excluded. We also excluded biopsies by providers who were not present during both study periods to account for provider mix.

Statistical Analysis
To evaluate for changes in the ratio of shave to punch biopsy utilization over time, we performed χ² tests. Because care practices may differ between private and academic settings as well as between physicians and mid-level providers, we performed subgroup analyses by practice setting and provider type.⁴

Results

We identified 11,785 biopsies (12.11% of which were punch) submitted for pathologic examination in May 2018 compared to 11,291 biopsies (12.08% of which were punch) in May 2019 (Table). The overall use of punch biopsies relative to shave biopsies did not change between the years. There was a relative decrease in punch biopsy use among academic practices (−1.88%; P=.032) and a relative increase in punch biopsy use among private practices (+0.90%; P=.043). Provider type was not associated with differing utilization of biopsy type.

Comment

Overall, there was not a considerable shift in utilization behavior from shave to punch biopsies after the introduction of new coding changes. However, our study does demonstrate a small yet significant increase in punch biopsy utilization among private practices, and a decrease among academic practices. Although the change in biopsy utilization behavior is small in magnitude, it may have a substantial impact when extrapolated to behavior across the entire United States.

We were unable to assess additional factors, such as clinical diagnosis, body site, and cosmetic concerns, that may impact biopsy type selection in this study. Although we included multiple study sites to improve generalizability, our findings may not be representative of all biopsies performed in the dermatology setting. The baseline difference in relative punch biopsy use in academic vs private practices may reflect differences in patient populations and chief concerns, but assuming these features are stable over a 1-year time period, our findings should remain valid. Future studies should focus on qualitative evaluations of physician decision-making and evaluate whether similar trends persist over time.

Conclusion

Skin biopsy utilization trends among differing practice and provider types should continue to be monitored to assess for longitudinal trends in utilization within the context of updated billing codes and associated reimbursements.

In 2019, the   2 Current Procedural Terminology (CPT) codes for skin biopsies (11100 and 11101) were replaced with 6 new CPT codes that   specify biopsy technique   and associated procedural complexity. ^1,2 Prior to the coding changes, all biopsies were reimbursed at the same payment level, but a punch biopsy (11104; national nonfacility Medicare payment, $133.29) is now reimbursed more than a shave biopsy (11102; national nonfacility Medicare payment, $106.42). ³ We sought to evaluate whether the decrease in reimbursement for shave biopsies and concurrent increase in reimbursement for punch biopsies led to a shift from shave to punch biopsy utilization.

Methods

We examined shave and punch biopsies submitted for pathologic examination at Brigham and Women’s Hospital, Massachusetts General Hospital, and Massachusetts General Physician’s Organization (all in Boston, Massachusetts), and Penn Medicine, University of Pennsylvania Health System (Philadelphia, Pennsylvania), in May 2018 vs May 2019 (four months after new codes were implemented). This study was approved by Partners HealthCare (Boston, Massachusetts) and the University of Pennsylvania institutional review boards.

We included shave and punch biopsies of skin performed by physician dermatologists and mid-level providers (ie, physician assistants, nurse practitioners) at dermatology practices. All biopsies performed by a technique other than shave or punch, unspecified biopsy type, consultation cases, nonskin biopsies (eg, mucosa), and biopsies performed at nondermatology practices were excluded. We also excluded biopsies by providers who were not present during both study periods to account for provider mix.

Statistical Analysis
To evaluate for changes in the ratio of shave to punch biopsy utilization over time, we performed χ² tests. Because care practices may differ between private and academic settings as well as between physicians and mid-level providers, we performed subgroup analyses by practice setting and provider type.⁴

Results

We identified 11,785 biopsies (12.11% of which were punch) submitted for pathologic examination in May 2018 compared to 11,291 biopsies (12.08% of which were punch) in May 2019 (Table). The overall use of punch biopsies relative to shave biopsies did not change between the years. There was a relative decrease in punch biopsy use among academic practices (−1.88%; P=.032) and a relative increase in punch biopsy use among private practices (+0.90%; P=.043). Provider type was not associated with differing utilization of biopsy type.

Comment

Overall, there was not a considerable shift in utilization behavior from shave to punch biopsies after the introduction of new coding changes. However, our study does demonstrate a small yet significant increase in punch biopsy utilization among private practices, and a decrease among academic practices. Although the change in biopsy utilization behavior is small in magnitude, it may have a substantial impact when extrapolated to behavior across the entire United States.

We were unable to assess additional factors, such as clinical diagnosis, body site, and cosmetic concerns, that may impact biopsy type selection in this study. Although we included multiple study sites to improve generalizability, our findings may not be representative of all biopsies performed in the dermatology setting. The baseline difference in relative punch biopsy use in academic vs private practices may reflect differences in patient populations and chief concerns, but assuming these features are stable over a 1-year time period, our findings should remain valid. Future studies should focus on qualitative evaluations of physician decision-making and evaluate whether similar trends persist over time.

Conclusion

Skin biopsy utilization trends among differing practice and provider types should continue to be monitored to assess for longitudinal trends in utilization within the context of updated billing codes and associated reimbursements.

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Extragenital Lichen Sclerosus Et Atrophicus 

Histopathologic evaluation revealed hyperkeratosis, follicular plugging, epidermal atrophy, and homogenization of papillary dermal collagen with an underlying lymphocytic infiltrate (Figure 1). Direct immunofluorescence of a plaque with a superimposed bulla was negative for deposition of C3, IgG, IgA, IgM, or fibrinogen. Accordingly, clinicopathologic correlation supported a diagnosis of extragenital lichen sclerosus et atrophicus (LSA). Of note, the patient's history of genital irritation was due to genital LSA that preceded the extragenital manifestations. 

Lichen sclerosus et atrophicus is an inflammatory dermatosis that typically presents as atrophic white papules of the anogenital area that coalesce into pruritic plaques; the exact etiology remains to be elucidated, yet various circulating autoantibodies have been identified, suggesting a role for autoimmunity.^1,2 Lichen sclerosus et atrophicus is more common in women than in men, with a bimodal peak in the age of onset affecting postmenopausal and prepubertal populations.¹ In women, affected areas include the labia minora and majora, clitoris, perineum, and perianal skin; LSA spares the mucosal surfaces of the vagina and cervix.² In men, uncircumscribed genital skin more commonly is affected. Involvement is localized to the foreskin and glans with occasional urethral involvement.²  

In contrast, extragenital LSA tends to present as asymptomatic papules and plaques that develop atrophy with time, involving the back, shoulders, neck, chest, thighs, axillae, and flexural wrists^2,3; an erythematous rim often is present,⁴ and hyperkeratosis with follicular plugging may be prominent.⁵ Our patient's case emphasizes the predilection of plaques for the chest and intermammary skin (Figure 2A). Approximately 15% of LSA cases have extragenital involvement, and extragenital-limited disease accounts for roughly 5% of cases.^6,7 Unlike genital LSA, extragenital disease has not been associated with an increased risk for squamous cell carcinoma.¹ Bullae formation within plaques of genital or extragenital LSA has been reported^3,8 and is exemplified in our patient (Figure 2B). Intralesional bullae formation likely is due to a combination of internal and external factors, mainly the inability to withstand shear forces due to an atrophic epidermis with basal vacuolar injury overlying an edematous papillary dermis with altered collagen.⁸ Dermatoscopic findings may aid in recognizing extragenital LSA9,¹⁰; our patient's plaques demonstrated the characteristic findings of comedolike openings, structureless white areas, and pink borders (Figure 3). 

The clinical differential diagnosis for well-demarcated, pink, scaly plaques is broad. Nummular eczema usually presents as coin-shaped eczematous plaques on the dorsal aspects of the hands or lower extremities, and histology shows epidermal spongiosis.¹¹ Nummular eczema may be considered due to the striking round morphology of various plaques, yet our patient's presentation was better served by a consideration of several papulosquamous disorders. 

Lichen planus (LP) presents as intensely pruritic, violaceous, polygonal, flat-topped papules with overlying reticular white lines, or Wickham striae, that favor the flexural wrists, lower back, and lower extremities. Lichen planus also may have oral and genital mucosal involvement. Similar to LSA, LP is more common in women and preferentially affects the postmenopausal population.¹² Additionally, hypertrophic LP may obscure Wickham striae and mimic extragenital LSA; distinguishing features of hypertrophic LP are intense pruritus and a predilection for the shins. Histology is defined by orthohyperkeratosis, hypergranulosis, sawtooth acanthosis, and vacuolar degeneration of the basal layer with Civatte bodies or dyskeratotic basal keratinocytes overlying a characteristic bandlike infiltrate of lymphocytes.¹² 

Lichen simplex chronicus (LSC) is characterized by intense pruritus and presents as hyperkeratotic plaques with a predilection for accessible regions such as the posterior neck and extremities.¹³ The striking annular demarcation of this case makes LSC unlikely. Comparable to LSA and LP, LSC also may present with both genital and extragenital findings. Histology of LSC is characterized by irregular acanthosis or thickening of the epidermis with vertical streaking of collagen and vascular bundles of the papillary dermis.¹³ 

Subacute cutaneous lupus erythematosus (SCLE) is important to consider for a new papulosquamous eruption with a predilection for the sun-exposed skin of a middle-aged woman. The presence of papules on the volar wrist and history of genital irritation, however, make this entity less likely. Similar to LSA, histologic examination of SCLE reveals epidermal atrophy, basal layer degeneration, and papillary dermal edema with lymphocytic inflammation. However, SCLE lacks the band of inflammation underlying pale homogenized papillary dermal collagen, the most distinguishing feature of LSA; instead, SCLE shows superficial and deep perivascular and periadnexal lymphocytes and mucin in the dermis.¹⁴ 

Lichen sclerosus et atrophicus may be chronic and progressive in nature or cycle through remissions and relapses.² Treatment is not curative, and management is directed to alleviating symptoms and preventing the progression of disease. First-line management of extragenital LSA is potent topical steroids.¹ Adjuvant topical calcineurin inhibitors may be used as steroid-sparing agents.² Phototherapy is a second-line therapy and even narrowband UVB phototherapy has demonstrated efficacy in managing extragenital LSA.^15,16 Our patient was started on mometasone ointment and calcipotriene cream with slight improvement after a 6-month trial. Ongoing management is focused on optimizing application of topical therapies.  

The Diagnosis: Cutaneous Metaplastic Synovial Cyst 

Gross examination of the excised nodule revealed a 2.5×1.2×1.0-cm, intact, gray-white, thin-walled, smooth-lined nodule filled with clear mucinouslike material. Hematoxylin and eosin-stained sections demonstrated a dermal-based cystlike structure composed of a lining of connective tissue with hyalinized material and fibrin as well as spindle and epithelioid cells with a mild mixed inflammatory infiltrate (Figure). These histopathologic findings led to the diagnosis of cutaneous metaplastic synovial cyst (CMSC).  

Cutaneous metaplastic synovial cyst, also known as synovial metaplasia of the skin, is an uncommon benign cystic lesion that was first reported by Gonzalez et al¹ in 1987. Histologically, CMSC lacks an epithelial lining and therefore is not a true cyst but rather a pseudocyst.² Clinically, the lesion typically presents as a solitary subcutaneous nodule that may be tender or painless. In a literature review of CMSC cases performed by Fukuyama et al,³ distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature,^3-9 including our present case. The pathogenesis remains uncertain; however, a majority of previously reported cases of CMSC characteristically have been associated with a pre-existing lesion, with most presentations developing at surgical scar sites secondary to operation or trauma.⁵ Relative tissue fragility secondary to rheumatoid arthritis¹⁰ and Ehlers-Danlos syndrome^9,11,12 has been linked to CMSC in some documented reports, while a minority of cases report no antecedent events triggering formation of the lesion.^13-15 

As evidenced by our patient, CMSC clinically mimics several other benign entities; histopathologic examination is necessary to confirm the diagnosis. Although nodular hidradenoma also may clinically present as a solitary firm intradermal nodule, microscopy reveals a dermal-based lobulated tumor containing cystic spaces and solid areas composed of basophilic polyhedral cells and round glycogen-filled clear cells.¹⁶ Epidermoid cysts are differentiated from CMSC by the presence of a cyst wall lining composed of stratified squamous epithelium and associated laminated keratin within the lumen,¹⁷ which corresponds to its pearly white appearance on gross examination. Cutaneous ciliated cysts predominantly occur on the lower extremities of young women and are lined by simple cuboidal or columnar ciliated cells that resemble müllerian epithelium.¹⁸ Similar to CMSC, ganglion cysts are pseudocysts that lack a true epithelial lining but differ in appearance due to their mucin-filled synovial-lined sac.¹⁹ Additionally, ganglion cysts most often occur on the dorsal and volar aspects of the wrist. 

Excisional biopsy is indicated as the preferred treatment of CMSC, given the lesion's benign behavior and low recurrence rate.⁶ Our case highlights this rare entity and reinforces its inclusion in the differential diagnosis of subcutaneous mobile nodules, especially in the setting of prior tissue injury secondary to trauma, surgical procedures, or conditions such as rheumatoid arthritis or Ehlers-Danlos syndrome. Unlike most previously reported cases, our patient reported no preceding tissue injury associated with formation of the lesion, and she was largely asymptomatic on presentation. Considering the limited number of CMSC cases demonstrated in the literature, it is important to continue reporting new cases to better understand characteristics and presentations of this uncommon lesion. 

The Diagnosis: Cutaneous Metaplastic Synovial Cyst 

Gross examination of the excised nodule revealed a 2.5×1.2×1.0-cm, intact, gray-white, thin-walled, smooth-lined nodule filled with clear mucinouslike material. Hematoxylin and eosin-stained sections demonstrated a dermal-based cystlike structure composed of a lining of connective tissue with hyalinized material and fibrin as well as spindle and epithelioid cells with a mild mixed inflammatory infiltrate (Figure). These histopathologic findings led to the diagnosis of cutaneous metaplastic synovial cyst (CMSC).  

Cutaneous metaplastic synovial cyst, also known as synovial metaplasia of the skin, is an uncommon benign cystic lesion that was first reported by Gonzalez et al¹ in 1987. Histologically, CMSC lacks an epithelial lining and therefore is not a true cyst but rather a pseudocyst.² Clinically, the lesion typically presents as a solitary subcutaneous nodule that may be tender or painless. In a literature review of CMSC cases performed by Fukuyama et al,³ distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature,^3-9 including our present case. The pathogenesis remains uncertain; however, a majority of previously reported cases of CMSC characteristically have been associated with a pre-existing lesion, with most presentations developing at surgical scar sites secondary to operation or trauma.⁵ Relative tissue fragility secondary to rheumatoid arthritis¹⁰ and Ehlers-Danlos syndrome^9,11,12 has been linked to CMSC in some documented reports, while a minority of cases report no antecedent events triggering formation of the lesion.^13-15 

As evidenced by our patient, CMSC clinically mimics several other benign entities; histopathologic examination is necessary to confirm the diagnosis. Although nodular hidradenoma also may clinically present as a solitary firm intradermal nodule, microscopy reveals a dermal-based lobulated tumor containing cystic spaces and solid areas composed of basophilic polyhedral cells and round glycogen-filled clear cells.¹⁶ Epidermoid cysts are differentiated from CMSC by the presence of a cyst wall lining composed of stratified squamous epithelium and associated laminated keratin within the lumen,¹⁷ which corresponds to its pearly white appearance on gross examination. Cutaneous ciliated cysts predominantly occur on the lower extremities of young women and are lined by simple cuboidal or columnar ciliated cells that resemble müllerian epithelium.¹⁸ Similar to CMSC, ganglion cysts are pseudocysts that lack a true epithelial lining but differ in appearance due to their mucin-filled synovial-lined sac.¹⁹ Additionally, ganglion cysts most often occur on the dorsal and volar aspects of the wrist. 

Excisional biopsy is indicated as the preferred treatment of CMSC, given the lesion's benign behavior and low recurrence rate.⁶ Our case highlights this rare entity and reinforces its inclusion in the differential diagnosis of subcutaneous mobile nodules, especially in the setting of prior tissue injury secondary to trauma, surgical procedures, or conditions such as rheumatoid arthritis or Ehlers-Danlos syndrome. Unlike most previously reported cases, our patient reported no preceding tissue injury associated with formation of the lesion, and she was largely asymptomatic on presentation. Considering the limited number of CMSC cases demonstrated in the literature, it is important to continue reporting new cases to better understand characteristics and presentations of this uncommon lesion. 

The Diagnosis: Cutaneous Metaplastic Synovial Cyst 

Gross examination of the excised nodule revealed a 2.5×1.2×1.0-cm, intact, gray-white, thin-walled, smooth-lined nodule filled with clear mucinouslike material. Hematoxylin and eosin-stained sections demonstrated a dermal-based cystlike structure composed of a lining of connective tissue with hyalinized material and fibrin as well as spindle and epithelioid cells with a mild mixed inflammatory infiltrate (Figure). These histopathologic findings led to the diagnosis of cutaneous metaplastic synovial cyst (CMSC).  

Cutaneous metaplastic synovial cyst, also known as synovial metaplasia of the skin, is an uncommon benign cystic lesion that was first reported by Gonzalez et al¹ in 1987. Histologically, CMSC lacks an epithelial lining and therefore is not a true cyst but rather a pseudocyst.² Clinically, the lesion typically presents as a solitary subcutaneous nodule that may be tender or painless. In a literature review of CMSC cases performed by Fukuyama et al,³ distribution of reported cases according to body site varied; however, limbs were found to be the most commonly involved area. A PubMed search of articles indexed for MEDLINE as well as a Google Scholar search using the term cutaneous metaplastic synovial cyst revealed at least 37 cases reported in the English-language literature,^3-9 including our present case. The pathogenesis remains uncertain; however, a majority of previously reported cases of CMSC characteristically have been associated with a pre-existing lesion, with most presentations developing at surgical scar sites secondary to operation or trauma.⁵ Relative tissue fragility secondary to rheumatoid arthritis¹⁰ and Ehlers-Danlos syndrome^9,11,12 has been linked to CMSC in some documented reports, while a minority of cases report no antecedent events triggering formation of the lesion.^13-15 

As evidenced by our patient, CMSC clinically mimics several other benign entities; histopathologic examination is necessary to confirm the diagnosis. Although nodular hidradenoma also may clinically present as a solitary firm intradermal nodule, microscopy reveals a dermal-based lobulated tumor containing cystic spaces and solid areas composed of basophilic polyhedral cells and round glycogen-filled clear cells.¹⁶ Epidermoid cysts are differentiated from CMSC by the presence of a cyst wall lining composed of stratified squamous epithelium and associated laminated keratin within the lumen,¹⁷ which corresponds to its pearly white appearance on gross examination. Cutaneous ciliated cysts predominantly occur on the lower extremities of young women and are lined by simple cuboidal or columnar ciliated cells that resemble müllerian epithelium.¹⁸ Similar to CMSC, ganglion cysts are pseudocysts that lack a true epithelial lining but differ in appearance due to their mucin-filled synovial-lined sac.¹⁹ Additionally, ganglion cysts most often occur on the dorsal and volar aspects of the wrist. 

Excisional biopsy is indicated as the preferred treatment of CMSC, given the lesion's benign behavior and low recurrence rate.⁶ Our case highlights this rare entity and reinforces its inclusion in the differential diagnosis of subcutaneous mobile nodules, especially in the setting of prior tissue injury secondary to trauma, surgical procedures, or conditions such as rheumatoid arthritis or Ehlers-Danlos syndrome. Unlike most previously reported cases, our patient reported no preceding tissue injury associated with formation of the lesion, and she was largely asymptomatic on presentation. Considering the limited number of CMSC cases demonstrated in the literature, it is important to continue reporting new cases to better understand characteristics and presentations of this uncommon lesion. 

The Diagnosis: Epidermodysplasia Verruciformis 

Histopathologic examination of our patient's biopsy specimen revealed mild acanthosis with prominent hypergranulosis and enlarged keratinocytes with blue-gray cytoplasm (Figure). A diagnosis of acquired epidermodysplasia verruciformis (EV) was rendered. The patient was treated with photodynamic therapy utilizing 5-aminolevulinic acid. 

Epidermodysplasia verruciformis is characterized by susceptibility to human papillomavirus (HPV) infections via a defect in cellular immunity. Epidermodysplasia verruciformis was first described as an autosomal-recessive genodermatosis, but it can be acquired in immunosuppressed states with an atypical clinical appearance.¹ There are few case reports in skin of color. Acquired EV appears in patients with acquired immunodeficiencies that are susceptible to EV-causing HPVs via a similar mechanism found in inherited EV.² The most common HPV serotypes involved in EV are HPV-5 and HPV-8. The duration of immunosuppression has been found to be positively correlated with the risk for EV development, with the majority of patients developing lesions after 5 years of immunosuppression.³ There is an approximately 60% risk of malignant transformation of EV lesions into nonmelanoma skin cancer.² This risk is believed to be lower in patients with darker skin.⁴  

Preventative measures including sun protection and annual surveillance are crucial in EV patients given the high rate of malignant transformation in sun-exposed lesions.⁵ Treatment options for EV are anecdotal and have variable results, ranging from topicals including 5-fluorouracil and imiquimod to systemic medications including acitretin and interferon.³ Photodynamic therapy can be used for extensive EV. Surgical modalities and other destructive methods also have been tried.⁶ 

Epidermodysplasia verruciformis often can be confused with similar dermatoses. Porokeratosis appears as annular pink papules with waferlike peripheral scales. Tinea versicolor is a dermatophyte infection caused by Malassezia furfur and presents as multiple dyspigmented, finely scaling, thin papules and plaques. Subacute cutaneous lupus erythematosus presents as pink, scaly, annular or psoriasiform papules and plaques most commonly on the trunk. Discoid lupus erythematosus presents as pink, hypopigmented or depigmented, atrophic plaques with a peripheral rim of erythema that indicates activity. Secondary syphilis, commonly denoted as the "great mimicker," presents as psoriasiform papules and plaques among other variable morphologies. 

The Diagnosis: Epidermodysplasia Verruciformis 

Histopathologic examination of our patient's biopsy specimen revealed mild acanthosis with prominent hypergranulosis and enlarged keratinocytes with blue-gray cytoplasm (Figure). A diagnosis of acquired epidermodysplasia verruciformis (EV) was rendered. The patient was treated with photodynamic therapy utilizing 5-aminolevulinic acid. 

Epidermodysplasia verruciformis is characterized by susceptibility to human papillomavirus (HPV) infections via a defect in cellular immunity. Epidermodysplasia verruciformis was first described as an autosomal-recessive genodermatosis, but it can be acquired in immunosuppressed states with an atypical clinical appearance.¹ There are few case reports in skin of color. Acquired EV appears in patients with acquired immunodeficiencies that are susceptible to EV-causing HPVs via a similar mechanism found in inherited EV.² The most common HPV serotypes involved in EV are HPV-5 and HPV-8. The duration of immunosuppression has been found to be positively correlated with the risk for EV development, with the majority of patients developing lesions after 5 years of immunosuppression.³ There is an approximately 60% risk of malignant transformation of EV lesions into nonmelanoma skin cancer.² This risk is believed to be lower in patients with darker skin.⁴  

Preventative measures including sun protection and annual surveillance are crucial in EV patients given the high rate of malignant transformation in sun-exposed lesions.⁵ Treatment options for EV are anecdotal and have variable results, ranging from topicals including 5-fluorouracil and imiquimod to systemic medications including acitretin and interferon.³ Photodynamic therapy can be used for extensive EV. Surgical modalities and other destructive methods also have been tried.⁶ 

Epidermodysplasia verruciformis often can be confused with similar dermatoses. Porokeratosis appears as annular pink papules with waferlike peripheral scales. Tinea versicolor is a dermatophyte infection caused by Malassezia furfur and presents as multiple dyspigmented, finely scaling, thin papules and plaques. Subacute cutaneous lupus erythematosus presents as pink, scaly, annular or psoriasiform papules and plaques most commonly on the trunk. Discoid lupus erythematosus presents as pink, hypopigmented or depigmented, atrophic plaques with a peripheral rim of erythema that indicates activity. Secondary syphilis, commonly denoted as the "great mimicker," presents as psoriasiform papules and plaques among other variable morphologies. 

The Diagnosis: Epidermodysplasia Verruciformis 

Histopathologic examination of our patient's biopsy specimen revealed mild acanthosis with prominent hypergranulosis and enlarged keratinocytes with blue-gray cytoplasm (Figure). A diagnosis of acquired epidermodysplasia verruciformis (EV) was rendered. The patient was treated with photodynamic therapy utilizing 5-aminolevulinic acid. 

Epidermodysplasia verruciformis is characterized by susceptibility to human papillomavirus (HPV) infections via a defect in cellular immunity. Epidermodysplasia verruciformis was first described as an autosomal-recessive genodermatosis, but it can be acquired in immunosuppressed states with an atypical clinical appearance.¹ There are few case reports in skin of color. Acquired EV appears in patients with acquired immunodeficiencies that are susceptible to EV-causing HPVs via a similar mechanism found in inherited EV.² The most common HPV serotypes involved in EV are HPV-5 and HPV-8. The duration of immunosuppression has been found to be positively correlated with the risk for EV development, with the majority of patients developing lesions after 5 years of immunosuppression.³ There is an approximately 60% risk of malignant transformation of EV lesions into nonmelanoma skin cancer.² This risk is believed to be lower in patients with darker skin.⁴  

Preventative measures including sun protection and annual surveillance are crucial in EV patients given the high rate of malignant transformation in sun-exposed lesions.⁵ Treatment options for EV are anecdotal and have variable results, ranging from topicals including 5-fluorouracil and imiquimod to systemic medications including acitretin and interferon.³ Photodynamic therapy can be used for extensive EV. Surgical modalities and other destructive methods also have been tried.⁶ 

Epidermodysplasia verruciformis often can be confused with similar dermatoses. Porokeratosis appears as annular pink papules with waferlike peripheral scales. Tinea versicolor is a dermatophyte infection caused by Malassezia furfur and presents as multiple dyspigmented, finely scaling, thin papules and plaques. Subacute cutaneous lupus erythematosus presents as pink, scaly, annular or psoriasiform papules and plaques most commonly on the trunk. Discoid lupus erythematosus presents as pink, hypopigmented or depigmented, atrophic plaques with a peripheral rim of erythema that indicates activity. Secondary syphilis, commonly denoted as the "great mimicker," presents as psoriasiform papules and plaques among other variable morphologies. 

The Diagnosis: Targetoid Hemosiderotic Hemangioma 

Targetoid hemosiderotic hemangioma (THH), also known as hobnail hemangioma, is a benign vascular tumor that usually occurs in young or middle-aged adults. It most commonly presents on the extremities or trunk as an isolated red-brown plaque or papule.^1,2 Histologically, THH is characterized by superficial dilated ectatic vessels with underlying proliferating vascular channels lined by plump hobnail endothelial cells.¹ Targetoid hemosiderotic hemangioma typically involves the dermis and spares the subcutis. The vascular channels may contain erythrocytes as well as pale eosinophilic lymph, as seen in our patient (quiz image). The deeper dermis contains vascular spaces that are more angulated and smaller and appear to be dissecting through the collagen bundles or collapsed.^1,3 A variable amount of hemosiderin deposition and extravasated erythrocytes are seen.^2,3 Histologic features evolve with the age of the lesion. Increasing amounts of hemosiderin deposition and erythrocyte extravasation may correspond histologically to the recent clinical color change reported by the patient.  

Verrucous hemangioma is a rare congenital vascular abnormality that is characterized by dilated vessels in the papillary dermis along with acanthosis, hyperkeratosis, and irregular papillomatosis, as seen in angiokeratoma.⁴ However, the vascular proliferation composed of variably sized, thin-walled capillaries extends into the deep dermis as well as the subcutis (Figure 1). Verrucous hemangioma most commonly is reported on the legs and generally starts as a violaceous patch that progresses into a hyperkeratotic verrucous plaque or nodule.^5,6  

Angiokeratoma is characterized by superficial vascular ectasia of the papillary dermis in association with overlying acanthosis, hyperkeratosis, and rete elongation.⁷ The dilated vascular spaces appear encircled by the epidermis (Figure 2). Intravascular thrombosis can be seen within the ectatic vessels.⁷ In contrast to verrucous hemangioma, angiokeratoma is limited to the papillary dermis. Therefore, obtaining a biopsy of sufficient depth is necessary for differentiation.⁸ There are 5 clinical presentations of angiokeratoma: sporadic, angiokeratoma of Mibelli, angiokeratoma of Fordyce, angiokeratoma circumscriptum, and angiokeratoma corporis diffusum (Fabry disease). Angiokeratomas may present on the lower extremities, tongue, trunk, and scrotum as hyperkeratotic, dark red to purple or black papules.⁷ 

There are 3 clinical stages of Kaposi sarcoma: patch, plaque, and nodular stages. The patch stage is characterized histologically by vascular channels that dissect through the dermis and extend around native vessels (the promontory sign)(Figure 3).^9,10 These features can show histologic overlap with THH. The plaque stage shows a more diffuse dermal vascular proliferation, increased cellularity of spindle cells, and possible extension into the subcutis.^9,10 Focal plasma cells, hemosiderin, and extravasated red blood cells can be seen. The nodular stage is characterized by a proliferation of spindle cells with red blood cells squeezed between slitlike vascular spaces, hyaline globules, and scattered mitotic figures, but not atypical forms.¹⁰ In this stage, plasma cells and hemosiderin are more readily identifiable. A biopsy from the nodular stage is unlikely to enter the histologic differential diagnosis with THH. Clinically, there are 4 variants of Kaposi sarcoma: the classic or sporadic form, an endemic form, iatrogenic, and AIDS associated. Overall, it is more common in males and can occur at any age.¹⁰ Human herpesvirus 8 is seen in all forms, and infected cells can be highlighted by the immunohistochemical stain for latent nuclear antigen 1.^9,10 

Angiosarcoma is a malignant endothelial tumor of soft tissue, skin, bone, and visceral organs.^11,12 Clinically, cutaneous angiosarcoma can present in a variety of ways, including single or multiple bluish red lesions that can ulcerate or bleed; violaceous nodules or plaques; and hematomalike lesions that can mimic epithelial neoplasms including squamous cell carcinoma, basal cell carcinoma, and malignant melanoma.^11,13,14 The cutaneous lesions most commonly occur on sun-exposed skin, particularly on the face and scalp.¹² Other clinical variants that are important to recognize are postradiation angiosarcoma, characterized by MYC gene amplification, and lymphedema-associated angiosarcoma (Stewart-Treves syndrome). Angiosarcoma can have a variety of morphologic features, ranging from well to poorly differentiated. Classically, angiosarcoma is characterized by infiltrating vascular spaces lined by atypical endothelial cells (Figure 4). Poorly differentiated angiosarcoma can demonstrate spindle, epithelioid, or polygonal cells with increased mitotic activity, pleomorphism, and irregular vascular spaces.¹¹ Endothelial markers such as ERG (erythroblast transformation specific-related gene)(nuclear) and CD31 (membranous) can be used to aid in the diagnosis of a poorly differentiated lesion. Epithelioid angiosarcoma also occasionally stains with cytokeratins.^13,14  

The Diagnosis: Targetoid Hemosiderotic Hemangioma 

Targetoid hemosiderotic hemangioma (THH), also known as hobnail hemangioma, is a benign vascular tumor that usually occurs in young or middle-aged adults. It most commonly presents on the extremities or trunk as an isolated red-brown plaque or papule.^1,2 Histologically, THH is characterized by superficial dilated ectatic vessels with underlying proliferating vascular channels lined by plump hobnail endothelial cells.¹ Targetoid hemosiderotic hemangioma typically involves the dermis and spares the subcutis. The vascular channels may contain erythrocytes as well as pale eosinophilic lymph, as seen in our patient (quiz image). The deeper dermis contains vascular spaces that are more angulated and smaller and appear to be dissecting through the collagen bundles or collapsed.^1,3 A variable amount of hemosiderin deposition and extravasated erythrocytes are seen.^2,3 Histologic features evolve with the age of the lesion. Increasing amounts of hemosiderin deposition and erythrocyte extravasation may correspond histologically to the recent clinical color change reported by the patient.  

Verrucous hemangioma is a rare congenital vascular abnormality that is characterized by dilated vessels in the papillary dermis along with acanthosis, hyperkeratosis, and irregular papillomatosis, as seen in angiokeratoma.⁴ However, the vascular proliferation composed of variably sized, thin-walled capillaries extends into the deep dermis as well as the subcutis (Figure 1). Verrucous hemangioma most commonly is reported on the legs and generally starts as a violaceous patch that progresses into a hyperkeratotic verrucous plaque or nodule.^5,6  

Angiokeratoma is characterized by superficial vascular ectasia of the papillary dermis in association with overlying acanthosis, hyperkeratosis, and rete elongation.⁷ The dilated vascular spaces appear encircled by the epidermis (Figure 2). Intravascular thrombosis can be seen within the ectatic vessels.⁷ In contrast to verrucous hemangioma, angiokeratoma is limited to the papillary dermis. Therefore, obtaining a biopsy of sufficient depth is necessary for differentiation.⁸ There are 5 clinical presentations of angiokeratoma: sporadic, angiokeratoma of Mibelli, angiokeratoma of Fordyce, angiokeratoma circumscriptum, and angiokeratoma corporis diffusum (Fabry disease). Angiokeratomas may present on the lower extremities, tongue, trunk, and scrotum as hyperkeratotic, dark red to purple or black papules.⁷ 

There are 3 clinical stages of Kaposi sarcoma: patch, plaque, and nodular stages. The patch stage is characterized histologically by vascular channels that dissect through the dermis and extend around native vessels (the promontory sign)(Figure 3).^9,10 These features can show histologic overlap with THH. The plaque stage shows a more diffuse dermal vascular proliferation, increased cellularity of spindle cells, and possible extension into the subcutis.^9,10 Focal plasma cells, hemosiderin, and extravasated red blood cells can be seen. The nodular stage is characterized by a proliferation of spindle cells with red blood cells squeezed between slitlike vascular spaces, hyaline globules, and scattered mitotic figures, but not atypical forms.¹⁰ In this stage, plasma cells and hemosiderin are more readily identifiable. A biopsy from the nodular stage is unlikely to enter the histologic differential diagnosis with THH. Clinically, there are 4 variants of Kaposi sarcoma: the classic or sporadic form, an endemic form, iatrogenic, and AIDS associated. Overall, it is more common in males and can occur at any age.¹⁰ Human herpesvirus 8 is seen in all forms, and infected cells can be highlighted by the immunohistochemical stain for latent nuclear antigen 1.^9,10 

Angiosarcoma is a malignant endothelial tumor of soft tissue, skin, bone, and visceral organs.^11,12 Clinically, cutaneous angiosarcoma can present in a variety of ways, including single or multiple bluish red lesions that can ulcerate or bleed; violaceous nodules or plaques; and hematomalike lesions that can mimic epithelial neoplasms including squamous cell carcinoma, basal cell carcinoma, and malignant melanoma.^11,13,14 The cutaneous lesions most commonly occur on sun-exposed skin, particularly on the face and scalp.¹² Other clinical variants that are important to recognize are postradiation angiosarcoma, characterized by MYC gene amplification, and lymphedema-associated angiosarcoma (Stewart-Treves syndrome). Angiosarcoma can have a variety of morphologic features, ranging from well to poorly differentiated. Classically, angiosarcoma is characterized by infiltrating vascular spaces lined by atypical endothelial cells (Figure 4). Poorly differentiated angiosarcoma can demonstrate spindle, epithelioid, or polygonal cells with increased mitotic activity, pleomorphism, and irregular vascular spaces.¹¹ Endothelial markers such as ERG (erythroblast transformation specific-related gene)(nuclear) and CD31 (membranous) can be used to aid in the diagnosis of a poorly differentiated lesion. Epithelioid angiosarcoma also occasionally stains with cytokeratins.^13,14  

The Diagnosis: Targetoid Hemosiderotic Hemangioma 

Targetoid hemosiderotic hemangioma (THH), also known as hobnail hemangioma, is a benign vascular tumor that usually occurs in young or middle-aged adults. It most commonly presents on the extremities or trunk as an isolated red-brown plaque or papule.^1,2 Histologically, THH is characterized by superficial dilated ectatic vessels with underlying proliferating vascular channels lined by plump hobnail endothelial cells.¹ Targetoid hemosiderotic hemangioma typically involves the dermis and spares the subcutis. The vascular channels may contain erythrocytes as well as pale eosinophilic lymph, as seen in our patient (quiz image). The deeper dermis contains vascular spaces that are more angulated and smaller and appear to be dissecting through the collagen bundles or collapsed.^1,3 A variable amount of hemosiderin deposition and extravasated erythrocytes are seen.^2,3 Histologic features evolve with the age of the lesion. Increasing amounts of hemosiderin deposition and erythrocyte extravasation may correspond histologically to the recent clinical color change reported by the patient.  

Verrucous hemangioma is a rare congenital vascular abnormality that is characterized by dilated vessels in the papillary dermis along with acanthosis, hyperkeratosis, and irregular papillomatosis, as seen in angiokeratoma.⁴ However, the vascular proliferation composed of variably sized, thin-walled capillaries extends into the deep dermis as well as the subcutis (Figure 1). Verrucous hemangioma most commonly is reported on the legs and generally starts as a violaceous patch that progresses into a hyperkeratotic verrucous plaque or nodule.^5,6  

Angiokeratoma is characterized by superficial vascular ectasia of the papillary dermis in association with overlying acanthosis, hyperkeratosis, and rete elongation.⁷ The dilated vascular spaces appear encircled by the epidermis (Figure 2). Intravascular thrombosis can be seen within the ectatic vessels.⁷ In contrast to verrucous hemangioma, angiokeratoma is limited to the papillary dermis. Therefore, obtaining a biopsy of sufficient depth is necessary for differentiation.⁸ There are 5 clinical presentations of angiokeratoma: sporadic, angiokeratoma of Mibelli, angiokeratoma of Fordyce, angiokeratoma circumscriptum, and angiokeratoma corporis diffusum (Fabry disease). Angiokeratomas may present on the lower extremities, tongue, trunk, and scrotum as hyperkeratotic, dark red to purple or black papules.⁷ 

There are 3 clinical stages of Kaposi sarcoma: patch, plaque, and nodular stages. The patch stage is characterized histologically by vascular channels that dissect through the dermis and extend around native vessels (the promontory sign)(Figure 3).^9,10 These features can show histologic overlap with THH. The plaque stage shows a more diffuse dermal vascular proliferation, increased cellularity of spindle cells, and possible extension into the subcutis.^9,10 Focal plasma cells, hemosiderin, and extravasated red blood cells can be seen. The nodular stage is characterized by a proliferation of spindle cells with red blood cells squeezed between slitlike vascular spaces, hyaline globules, and scattered mitotic figures, but not atypical forms.¹⁰ In this stage, plasma cells and hemosiderin are more readily identifiable. A biopsy from the nodular stage is unlikely to enter the histologic differential diagnosis with THH. Clinically, there are 4 variants of Kaposi sarcoma: the classic or sporadic form, an endemic form, iatrogenic, and AIDS associated. Overall, it is more common in males and can occur at any age.¹⁰ Human herpesvirus 8 is seen in all forms, and infected cells can be highlighted by the immunohistochemical stain for latent nuclear antigen 1.^9,10 

Angiosarcoma is a malignant endothelial tumor of soft tissue, skin, bone, and visceral organs.^11,12 Clinically, cutaneous angiosarcoma can present in a variety of ways, including single or multiple bluish red lesions that can ulcerate or bleed; violaceous nodules or plaques; and hematomalike lesions that can mimic epithelial neoplasms including squamous cell carcinoma, basal cell carcinoma, and malignant melanoma.^11,13,14 The cutaneous lesions most commonly occur on sun-exposed skin, particularly on the face and scalp.¹² Other clinical variants that are important to recognize are postradiation angiosarcoma, characterized by MYC gene amplification, and lymphedema-associated angiosarcoma (Stewart-Treves syndrome). Angiosarcoma can have a variety of morphologic features, ranging from well to poorly differentiated. Classically, angiosarcoma is characterized by infiltrating vascular spaces lined by atypical endothelial cells (Figure 4). Poorly differentiated angiosarcoma can demonstrate spindle, epithelioid, or polygonal cells with increased mitotic activity, pleomorphism, and irregular vascular spaces.¹¹ Endothelial markers such as ERG (erythroblast transformation specific-related gene)(nuclear) and CD31 (membranous) can be used to aid in the diagnosis of a poorly differentiated lesion. Epithelioid angiosarcoma also occasionally stains with cytokeratins.^13,14  

The term osteoma cutis (OC) is defined as the ossification or bone formation either in the dermis or hypodermis. ¹ It is heterotopic in nature, referring to extraneous bone formation in soft tissue. Osteoma cutis was first described in 1858 ^2,3 ; in 1868, the multiple miliary form on the face was described. ⁴ Cutaneous ossification can take many forms, ranging from occurrence in a nevus (nevus of Nanta) to its association with rare genetic disorders, such as fibrodysplasia ossificans progressiva and Albright hereditary osteodystrophy.

Some of these ossifications are classified as primary; others are secondary, depending on the presence of a preexisting lesion (eg, pilomatricoma, basal cell carcinoma). However, certain conditions, such as multiple miliary osteoma of the face, can be difficult to classify due to the presence or absence of a history of acne or dermabrasion, or both. The secondary forms more commonly are encountered due to their incidental association with an excised lesion, such as pilomatricoma.

A precursor of OC has been neglected in the literature despite its common occurrence. It may have been peripherally alluded to in the literature in reference to the miliary form of OC.^5,6 The cases reported here demonstrate small round nodules of calcification or ossification, or both, in punch biopsies and excision specimens from hair-bearing areas of skin, especially from the head and neck. These lesions are mainly observed in the peripilar location or more specifically in the approximate location of the hair bulb.

This article reviews a possible mechanism of formation of these osteocalcific micronodules. These often-encountered micronodules are small osteocalcific lesions without typical bone or well-formed OC, such as trabeculae formation or fatty marrow, and may represent earliest stages in the formation of OC.

Clinical Observations

During routine dermatopathologic practice, I observed incidental small osteocalcific micronodules in close proximity to the lower part of the hair follicle in multiple cases. These nodules were not related to the main lesion in the specimen and were not the reason for the biopsy or excision. Most of the time, these micronodules were noted in excision or re-excision specimens or in a punch biopsy.

In my review of multiple unrelated cases over time, incidental osteocalcific micronodules were observed occasionally in punch biopsies and excision specimens during routine practice. These micronodules were mainly located in the vicinity of a hair bulb (Figure 1). If the hair bulb was not present in the sections, these micronodules were noted near or within the fibrous tract (Figure 2) or beneath a sebaceous lobule (Figure 3). In an exceptional case, a small round deposit of osteoid was seen forming just above the dermal papilla of the hair bulb (Figure 4).

Multiple osteocalcific micronodules were identified in a case of cicatricial alopecia. These micronodules were observed in sections taken at the levels of hair bulbs, and more or less corresponded to the size of the bulb (Figure 5A). Fortuitously, the patient was dark-skinned; the remnants of melanin within the micronodules provided evidence that the micronodules were formed within hair bulbs. Melanin staining confirmed the presence of melanin within some of the micronodules (Figure 5B).

Comment

Skeletogenesis in humans takes place by 2 methods: endochondral ossification and intramembranous ossification. In contrast to endochondral ossification, intramembranous ossification does not require a preexisting cartilaginous template. Instead, there is condensation of mesenchymal cells, which differentiate into osteoblasts and lay down osteoid, thus forming an ossification center. Little is known about the mechanism of formation of OC or the nidus of formation of the primary form.

Incidental micronodules of calcification and ossification are routinely encountered during histopathologic review of specimens from hair-bearing areas of the skin in dermatopathology practice. A review of the literature, however, does not reveal any specific dermatopathologic term ascribed to this phenomenon. These lesions might be similar to those described by Hopkins⁵ in 1928 in the setting of miliary OC of the face secondary to acne. Rossman and Freeman⁶ also described the same lesions when referring to facial OC as a “stage of pre-osseous calcification.”

When these osteocalcific micronodules are encountered, it usually is in close proximity to a hair follicle bulb. When a hair bulb is not seen in the sections, the micronodules are noted near fibrous tracts, arrector pili muscles, or sebaceous lobules, suggesting a close peripilar or peribulbar location. The micronodules are approximately 0.5 mm in diameter—roughly the size of a hair bulb. Due to the close anatomic association of micronodules and the hair bulb, these lesions can be called pilar osteocalcific nodules (PONs).

The role of bone morphogenetic protein (BMP) signaling in the maintenance of the hair cycle is well established. Bone morphogenetic proteins are extracellular cytokines that belong to the transforming growth factor β family. The hair bulb microenvironment is rich in BMPs, which are essential in cross-talk between hair matrix cells and follicular dermal papilla (FDP) cells in the maintenance of the hair cycle, especially during cytodifferentiation.⁷ Follicular dermal papilla cells lose their hair follicle inductive properties in vitro in the absence of BMP signaling. Introducing BMP to the in vitro niche restores these molecular properties of FDP cells.⁸

As the name implies, BMPs were discovered in relation to their important role in osteogenesis and tissue homeostasis. More than 20 BMPs have been identified, many of which promote bone formation and repair of bone fracture. Osteoinductive BMPs include BMP-2 and BMP-4 through BMP-10; BMP-2 and BMP-4 are expressed in the hair matrix and BMP-4 and BMP-6 are expressed in the FDP.^8,9 All bone-inducing BMPs can cause mesenchymal stem cells to differentiate into osteoblasts in vitro.¹⁰

Overactive BMP signaling has been shown to cause heterotopic ossification in patients with fibrodysplasia ossificans progressiva.⁸ Immunohistochemical expression of BMP-2 has been demonstrated in shadow cells of pilomatricoma.¹¹ Calcification and ossification are seen in as many as 20% of pilomatricomas. Both BMP-2 and BMP-4 have been shown to induce osteogenic differentiation of mouse skin−derived fibroblasts and FDP cells.¹²

Myllylä et al¹³ described 4 cases of multiple miliary osteoma cutis (MMOC). They also found 47 reported cases of MMOC, in which there was a history of acne in 55% (26/47). Only 15% (7/47) of these cases were extrafacial on the neck, chest, back, and arms. Osteomas in these cases were not associated with folliculosebaceous units or other adnexal structures, which may have been due to replacement by acne scarring, as all 4 patients had a history of acne vulgaris. The authors postulated a role for the GNAS gene mutation in the morphogenesis of MMOC; however, no supporting evidence was found for this claim. They also postulated a role for BMPs in the formation of MMOC.¹³

Another interesting aspect of osteoma formation in human skin is the similarity to osteoderms or the integumentary skeleton of vertebrates.¹⁴ Early in evolution, the dermal skeleton was the predominant skeletal system in some lineages. Phylogenetically, osteoderms are not uniformly distributed, and show a latent ability to manifest in some groups or lay dormant or disappear in others. The occurrence of primary osteomas in the human integument might be a vestigial manifestation of deep homology,¹⁵ a latent ability to form structures that have been lost. The embryologic formation of osteoderms in the dermis of vertebrates is thought to depend on the interaction or cross-talk between ectomesenchymal cells of neural crest origin and cells of the stratum basalis of epidermis, which is somewhat similar to the formation of the hair follicles.

Conclusion

Under certain conditions, the bulb region of a hair follicle might provide a nidus for the formation of OC. The hair bulb region contains both the precursor cellular element (mesenchymal cells of FDP) and the trigger cytokine (BMP) for the induction of osteogenic metaplasia.

The term osteoma cutis (OC) is defined as the ossification or bone formation either in the dermis or hypodermis. ¹ It is heterotopic in nature, referring to extraneous bone formation in soft tissue. Osteoma cutis was first described in 1858 ^2,3 ; in 1868, the multiple miliary form on the face was described. ⁴ Cutaneous ossification can take many forms, ranging from occurrence in a nevus (nevus of Nanta) to its association with rare genetic disorders, such as fibrodysplasia ossificans progressiva and Albright hereditary osteodystrophy.

Some of these ossifications are classified as primary; others are secondary, depending on the presence of a preexisting lesion (eg, pilomatricoma, basal cell carcinoma). However, certain conditions, such as multiple miliary osteoma of the face, can be difficult to classify due to the presence or absence of a history of acne or dermabrasion, or both. The secondary forms more commonly are encountered due to their incidental association with an excised lesion, such as pilomatricoma.

A precursor of OC has been neglected in the literature despite its common occurrence. It may have been peripherally alluded to in the literature in reference to the miliary form of OC.^5,6 The cases reported here demonstrate small round nodules of calcification or ossification, or both, in punch biopsies and excision specimens from hair-bearing areas of skin, especially from the head and neck. These lesions are mainly observed in the peripilar location or more specifically in the approximate location of the hair bulb.

This article reviews a possible mechanism of formation of these osteocalcific micronodules. These often-encountered micronodules are small osteocalcific lesions without typical bone or well-formed OC, such as trabeculae formation or fatty marrow, and may represent earliest stages in the formation of OC.

Clinical Observations

During routine dermatopathologic practice, I observed incidental small osteocalcific micronodules in close proximity to the lower part of the hair follicle in multiple cases. These nodules were not related to the main lesion in the specimen and were not the reason for the biopsy or excision. Most of the time, these micronodules were noted in excision or re-excision specimens or in a punch biopsy.

In my review of multiple unrelated cases over time, incidental osteocalcific micronodules were observed occasionally in punch biopsies and excision specimens during routine practice. These micronodules were mainly located in the vicinity of a hair bulb (Figure 1). If the hair bulb was not present in the sections, these micronodules were noted near or within the fibrous tract (Figure 2) or beneath a sebaceous lobule (Figure 3). In an exceptional case, a small round deposit of osteoid was seen forming just above the dermal papilla of the hair bulb (Figure 4).

Multiple osteocalcific micronodules were identified in a case of cicatricial alopecia. These micronodules were observed in sections taken at the levels of hair bulbs, and more or less corresponded to the size of the bulb (Figure 5A). Fortuitously, the patient was dark-skinned; the remnants of melanin within the micronodules provided evidence that the micronodules were formed within hair bulbs. Melanin staining confirmed the presence of melanin within some of the micronodules (Figure 5B).

Comment

Skeletogenesis in humans takes place by 2 methods: endochondral ossification and intramembranous ossification. In contrast to endochondral ossification, intramembranous ossification does not require a preexisting cartilaginous template. Instead, there is condensation of mesenchymal cells, which differentiate into osteoblasts and lay down osteoid, thus forming an ossification center. Little is known about the mechanism of formation of OC or the nidus of formation of the primary form.

Incidental micronodules of calcification and ossification are routinely encountered during histopathologic review of specimens from hair-bearing areas of the skin in dermatopathology practice. A review of the literature, however, does not reveal any specific dermatopathologic term ascribed to this phenomenon. These lesions might be similar to those described by Hopkins⁵ in 1928 in the setting of miliary OC of the face secondary to acne. Rossman and Freeman⁶ also described the same lesions when referring to facial OC as a “stage of pre-osseous calcification.”

When these osteocalcific micronodules are encountered, it usually is in close proximity to a hair follicle bulb. When a hair bulb is not seen in the sections, the micronodules are noted near fibrous tracts, arrector pili muscles, or sebaceous lobules, suggesting a close peripilar or peribulbar location. The micronodules are approximately 0.5 mm in diameter—roughly the size of a hair bulb. Due to the close anatomic association of micronodules and the hair bulb, these lesions can be called pilar osteocalcific nodules (PONs).

The role of bone morphogenetic protein (BMP) signaling in the maintenance of the hair cycle is well established. Bone morphogenetic proteins are extracellular cytokines that belong to the transforming growth factor β family. The hair bulb microenvironment is rich in BMPs, which are essential in cross-talk between hair matrix cells and follicular dermal papilla (FDP) cells in the maintenance of the hair cycle, especially during cytodifferentiation.⁷ Follicular dermal papilla cells lose their hair follicle inductive properties in vitro in the absence of BMP signaling. Introducing BMP to the in vitro niche restores these molecular properties of FDP cells.⁸

As the name implies, BMPs were discovered in relation to their important role in osteogenesis and tissue homeostasis. More than 20 BMPs have been identified, many of which promote bone formation and repair of bone fracture. Osteoinductive BMPs include BMP-2 and BMP-4 through BMP-10; BMP-2 and BMP-4 are expressed in the hair matrix and BMP-4 and BMP-6 are expressed in the FDP.^8,9 All bone-inducing BMPs can cause mesenchymal stem cells to differentiate into osteoblasts in vitro.¹⁰

Overactive BMP signaling has been shown to cause heterotopic ossification in patients with fibrodysplasia ossificans progressiva.⁸ Immunohistochemical expression of BMP-2 has been demonstrated in shadow cells of pilomatricoma.¹¹ Calcification and ossification are seen in as many as 20% of pilomatricomas. Both BMP-2 and BMP-4 have been shown to induce osteogenic differentiation of mouse skin−derived fibroblasts and FDP cells.¹²

Myllylä et al¹³ described 4 cases of multiple miliary osteoma cutis (MMOC). They also found 47 reported cases of MMOC, in which there was a history of acne in 55% (26/47). Only 15% (7/47) of these cases were extrafacial on the neck, chest, back, and arms. Osteomas in these cases were not associated with folliculosebaceous units or other adnexal structures, which may have been due to replacement by acne scarring, as all 4 patients had a history of acne vulgaris. The authors postulated a role for the GNAS gene mutation in the morphogenesis of MMOC; however, no supporting evidence was found for this claim. They also postulated a role for BMPs in the formation of MMOC.¹³

Another interesting aspect of osteoma formation in human skin is the similarity to osteoderms or the integumentary skeleton of vertebrates.¹⁴ Early in evolution, the dermal skeleton was the predominant skeletal system in some lineages. Phylogenetically, osteoderms are not uniformly distributed, and show a latent ability to manifest in some groups or lay dormant or disappear in others. The occurrence of primary osteomas in the human integument might be a vestigial manifestation of deep homology,¹⁵ a latent ability to form structures that have been lost. The embryologic formation of osteoderms in the dermis of vertebrates is thought to depend on the interaction or cross-talk between ectomesenchymal cells of neural crest origin and cells of the stratum basalis of epidermis, which is somewhat similar to the formation of the hair follicles.

Conclusion

Under certain conditions, the bulb region of a hair follicle might provide a nidus for the formation of OC. The hair bulb region contains both the precursor cellular element (mesenchymal cells of FDP) and the trigger cytokine (BMP) for the induction of osteogenic metaplasia.

The term osteoma cutis (OC) is defined as the ossification or bone formation either in the dermis or hypodermis. ¹ It is heterotopic in nature, referring to extraneous bone formation in soft tissue. Osteoma cutis was first described in 1858 ^2,3 ; in 1868, the multiple miliary form on the face was described. ⁴ Cutaneous ossification can take many forms, ranging from occurrence in a nevus (nevus of Nanta) to its association with rare genetic disorders, such as fibrodysplasia ossificans progressiva and Albright hereditary osteodystrophy.

Some of these ossifications are classified as primary; others are secondary, depending on the presence of a preexisting lesion (eg, pilomatricoma, basal cell carcinoma). However, certain conditions, such as multiple miliary osteoma of the face, can be difficult to classify due to the presence or absence of a history of acne or dermabrasion, or both. The secondary forms more commonly are encountered due to their incidental association with an excised lesion, such as pilomatricoma.

A precursor of OC has been neglected in the literature despite its common occurrence. It may have been peripherally alluded to in the literature in reference to the miliary form of OC.^5,6 The cases reported here demonstrate small round nodules of calcification or ossification, or both, in punch biopsies and excision specimens from hair-bearing areas of skin, especially from the head and neck. These lesions are mainly observed in the peripilar location or more specifically in the approximate location of the hair bulb.

This article reviews a possible mechanism of formation of these osteocalcific micronodules. These often-encountered micronodules are small osteocalcific lesions without typical bone or well-formed OC, such as trabeculae formation or fatty marrow, and may represent earliest stages in the formation of OC.

Clinical Observations

During routine dermatopathologic practice, I observed incidental small osteocalcific micronodules in close proximity to the lower part of the hair follicle in multiple cases. These nodules were not related to the main lesion in the specimen and were not the reason for the biopsy or excision. Most of the time, these micronodules were noted in excision or re-excision specimens or in a punch biopsy.

In my review of multiple unrelated cases over time, incidental osteocalcific micronodules were observed occasionally in punch biopsies and excision specimens during routine practice. These micronodules were mainly located in the vicinity of a hair bulb (Figure 1). If the hair bulb was not present in the sections, these micronodules were noted near or within the fibrous tract (Figure 2) or beneath a sebaceous lobule (Figure 3). In an exceptional case, a small round deposit of osteoid was seen forming just above the dermal papilla of the hair bulb (Figure 4).

Multiple osteocalcific micronodules were identified in a case of cicatricial alopecia. These micronodules were observed in sections taken at the levels of hair bulbs, and more or less corresponded to the size of the bulb (Figure 5A). Fortuitously, the patient was dark-skinned; the remnants of melanin within the micronodules provided evidence that the micronodules were formed within hair bulbs. Melanin staining confirmed the presence of melanin within some of the micronodules (Figure 5B).

Comment

Skeletogenesis in humans takes place by 2 methods: endochondral ossification and intramembranous ossification. In contrast to endochondral ossification, intramembranous ossification does not require a preexisting cartilaginous template. Instead, there is condensation of mesenchymal cells, which differentiate into osteoblasts and lay down osteoid, thus forming an ossification center. Little is known about the mechanism of formation of OC or the nidus of formation of the primary form.

Incidental micronodules of calcification and ossification are routinely encountered during histopathologic review of specimens from hair-bearing areas of the skin in dermatopathology practice. A review of the literature, however, does not reveal any specific dermatopathologic term ascribed to this phenomenon. These lesions might be similar to those described by Hopkins⁵ in 1928 in the setting of miliary OC of the face secondary to acne. Rossman and Freeman⁶ also described the same lesions when referring to facial OC as a “stage of pre-osseous calcification.”

When these osteocalcific micronodules are encountered, it usually is in close proximity to a hair follicle bulb. When a hair bulb is not seen in the sections, the micronodules are noted near fibrous tracts, arrector pili muscles, or sebaceous lobules, suggesting a close peripilar or peribulbar location. The micronodules are approximately 0.5 mm in diameter—roughly the size of a hair bulb. Due to the close anatomic association of micronodules and the hair bulb, these lesions can be called pilar osteocalcific nodules (PONs).

The role of bone morphogenetic protein (BMP) signaling in the maintenance of the hair cycle is well established. Bone morphogenetic proteins are extracellular cytokines that belong to the transforming growth factor β family. The hair bulb microenvironment is rich in BMPs, which are essential in cross-talk between hair matrix cells and follicular dermal papilla (FDP) cells in the maintenance of the hair cycle, especially during cytodifferentiation.⁷ Follicular dermal papilla cells lose their hair follicle inductive properties in vitro in the absence of BMP signaling. Introducing BMP to the in vitro niche restores these molecular properties of FDP cells.⁸

As the name implies, BMPs were discovered in relation to their important role in osteogenesis and tissue homeostasis. More than 20 BMPs have been identified, many of which promote bone formation and repair of bone fracture. Osteoinductive BMPs include BMP-2 and BMP-4 through BMP-10; BMP-2 and BMP-4 are expressed in the hair matrix and BMP-4 and BMP-6 are expressed in the FDP.^8,9 All bone-inducing BMPs can cause mesenchymal stem cells to differentiate into osteoblasts in vitro.¹⁰

Overactive BMP signaling has been shown to cause heterotopic ossification in patients with fibrodysplasia ossificans progressiva.⁸ Immunohistochemical expression of BMP-2 has been demonstrated in shadow cells of pilomatricoma.¹¹ Calcification and ossification are seen in as many as 20% of pilomatricomas. Both BMP-2 and BMP-4 have been shown to induce osteogenic differentiation of mouse skin−derived fibroblasts and FDP cells.¹²

Myllylä et al¹³ described 4 cases of multiple miliary osteoma cutis (MMOC). They also found 47 reported cases of MMOC, in which there was a history of acne in 55% (26/47). Only 15% (7/47) of these cases were extrafacial on the neck, chest, back, and arms. Osteomas in these cases were not associated with folliculosebaceous units or other adnexal structures, which may have been due to replacement by acne scarring, as all 4 patients had a history of acne vulgaris. The authors postulated a role for the GNAS gene mutation in the morphogenesis of MMOC; however, no supporting evidence was found for this claim. They also postulated a role for BMPs in the formation of MMOC.¹³

Another interesting aspect of osteoma formation in human skin is the similarity to osteoderms or the integumentary skeleton of vertebrates.¹⁴ Early in evolution, the dermal skeleton was the predominant skeletal system in some lineages. Phylogenetically, osteoderms are not uniformly distributed, and show a latent ability to manifest in some groups or lay dormant or disappear in others. The occurrence of primary osteomas in the human integument might be a vestigial manifestation of deep homology,¹⁵ a latent ability to form structures that have been lost. The embryologic formation of osteoderms in the dermis of vertebrates is thought to depend on the interaction or cross-talk between ectomesenchymal cells of neural crest origin and cells of the stratum basalis of epidermis, which is somewhat similar to the formation of the hair follicles.

Conclusion

Under certain conditions, the bulb region of a hair follicle might provide a nidus for the formation of OC. The hair bulb region contains both the precursor cellular element (mesenchymal cells of FDP) and the trigger cytokine (BMP) for the induction of osteogenic metaplasia.