Dermatopathology

To the Editor:

Figure 1. A 30-cm pink and violaceous, asymmetric, reticulated patch on the lateral aspect of the right thigh.

Figure 2. Histopathology revealed widely dilated vascular channels containing collections of histiocytes in the superficial dermis with adjacent features of chronic lymphedema (A)(H&E, original magnification ×10) as well as a collection of histiocytes in a dilated lymphatic channel (B)(H&E, original magnification ×40). D2-40 staining demonstrated ectatic lymphatic vessels in the upper dermins (C)(original magnification ×20).

A 70-year-old white man presented with an asymptomatic patch on the lateral aspect of the right thigh of 15 months’ duration. The patient believed the patch correlated with a hip replacement 3 years prior; however, it was 6 inches inferior to the incision site. Physical examination revealed a 30-cm pink and violaceous, asymmetric, reticulated patch (Figure 1). The patch was unresponsive to topical corticosteroids as well as a short course of oral prednisone. The patient’s medical history was notable for type 2 diabetes mellitus. Histopathologic examination revealed widely dilated vascular channels containing collections of histiocytes in the superficial dermis. In addition, adjacent features of chronic lymphedema were present, namely interstitial fibroplasia with dilated lymphatic vessels and a lymphoplasmacytic infiltrate (Figure 2). These findings were consistent with intralymphatic histiocytosis, a rare disease most commonly associated with rheumatoid arthritis. Our patient did not have a history or clinical symptoms of rheumatoid arthritis.

Intralymphatic histiocytosis is a rare cutaneous condition reported by O’Grady et al¹ in 1994. This condition has been most frequently associated with rheumatoid arthritis²; however, there has been an emerging association in patients with orthopedic metal implants, with and without a concomitant diagnosis of rheumatoid arthritis. Cases associated with metal implants are rare.^2-7

The condition presents as asymptomatic red, brown, or violaceous patches, plaques, papules, or nodules that are ill defined and tend to demonstrate a livedo reticularis–like pattern. The lesions typically are overlying or in close proximity to a joint. Histopathologic findings include dilated vascular structures in the reticular dermis, some with empty lumina and others containing collections of mononuclear histiocytes. There also may be an inflammatory infiltrate in the adjacent dermis composed of a mix of lymphocytes, plasma cells, and/or histiocytes. Endothelial cells lining the dilated lumina express immunoreactivity for CD31, CD34, D2-40, Lyve-1, and Prox-1. Intravascular histiocytes are positive for CD68 and CD31.⁶

The pathogenesis of intralymphatic histiocytosis remains undefined. Some hypothesize that intralymphatic histiocytosis could be the early stage of reactive angioendotheliomatosis, as these conditions share clinical and histological features.⁸ Reactive angioendotheliomatosis also is a rare condition that may present as erythematous to violaceous patches or plaques. The lesions are commonly found on the limbs and may be associated with constitutional symptoms. Histologic findings of reactive angioendotheliomatosis include a proliferation of epithelioid, round, or spindle-shaped cells within the lumina of dermal blood vessels, which show positivity for CD31 and CD34.⁹ Others suggest the lesions of intralymphatic histiocytosis arise from lymphangiectasia; obstruction of lymphatic drainage due to congenital abnormalities; or acquired damage from infection, trauma, surgery, or radiation.² Due to the common association with rheumatoid arthritis and orthopedic implants, it is likely that lymphatic stasis secondary to chronic inflammation plays a notable role.

Therapies such as topical and systemic corticosteroids, local radiotherapy, cyclophosphamide, pentoxifylline, and arthrocentesis have been attempted without evidence of efficacy.² Although intralymphatic histiocytosis is chronic and resistant to therapy, patients can be reassured that the condition runs a benign course.

To the Editor:

Figure 1. A 30-cm pink and violaceous, asymmetric, reticulated patch on the lateral aspect of the right thigh.

Figure 2. Histopathology revealed widely dilated vascular channels containing collections of histiocytes in the superficial dermis with adjacent features of chronic lymphedema (A)(H&E, original magnification ×10) as well as a collection of histiocytes in a dilated lymphatic channel (B)(H&E, original magnification ×40). D2-40 staining demonstrated ectatic lymphatic vessels in the upper dermins (C)(original magnification ×20).

A 70-year-old white man presented with an asymptomatic patch on the lateral aspect of the right thigh of 15 months’ duration. The patient believed the patch correlated with a hip replacement 3 years prior; however, it was 6 inches inferior to the incision site. Physical examination revealed a 30-cm pink and violaceous, asymmetric, reticulated patch (Figure 1). The patch was unresponsive to topical corticosteroids as well as a short course of oral prednisone. The patient’s medical history was notable for type 2 diabetes mellitus. Histopathologic examination revealed widely dilated vascular channels containing collections of histiocytes in the superficial dermis. In addition, adjacent features of chronic lymphedema were present, namely interstitial fibroplasia with dilated lymphatic vessels and a lymphoplasmacytic infiltrate (Figure 2). These findings were consistent with intralymphatic histiocytosis, a rare disease most commonly associated with rheumatoid arthritis. Our patient did not have a history or clinical symptoms of rheumatoid arthritis.

Intralymphatic histiocytosis is a rare cutaneous condition reported by O’Grady et al¹ in 1994. This condition has been most frequently associated with rheumatoid arthritis²; however, there has been an emerging association in patients with orthopedic metal implants, with and without a concomitant diagnosis of rheumatoid arthritis. Cases associated with metal implants are rare.^2-7

The condition presents as asymptomatic red, brown, or violaceous patches, plaques, papules, or nodules that are ill defined and tend to demonstrate a livedo reticularis–like pattern. The lesions typically are overlying or in close proximity to a joint. Histopathologic findings include dilated vascular structures in the reticular dermis, some with empty lumina and others containing collections of mononuclear histiocytes. There also may be an inflammatory infiltrate in the adjacent dermis composed of a mix of lymphocytes, plasma cells, and/or histiocytes. Endothelial cells lining the dilated lumina express immunoreactivity for CD31, CD34, D2-40, Lyve-1, and Prox-1. Intravascular histiocytes are positive for CD68 and CD31.⁶

The pathogenesis of intralymphatic histiocytosis remains undefined. Some hypothesize that intralymphatic histiocytosis could be the early stage of reactive angioendotheliomatosis, as these conditions share clinical and histological features.⁸ Reactive angioendotheliomatosis also is a rare condition that may present as erythematous to violaceous patches or plaques. The lesions are commonly found on the limbs and may be associated with constitutional symptoms. Histologic findings of reactive angioendotheliomatosis include a proliferation of epithelioid, round, or spindle-shaped cells within the lumina of dermal blood vessels, which show positivity for CD31 and CD34.⁹ Others suggest the lesions of intralymphatic histiocytosis arise from lymphangiectasia; obstruction of lymphatic drainage due to congenital abnormalities; or acquired damage from infection, trauma, surgery, or radiation.² Due to the common association with rheumatoid arthritis and orthopedic implants, it is likely that lymphatic stasis secondary to chronic inflammation plays a notable role.

Therapies such as topical and systemic corticosteroids, local radiotherapy, cyclophosphamide, pentoxifylline, and arthrocentesis have been attempted without evidence of efficacy.² Although intralymphatic histiocytosis is chronic and resistant to therapy, patients can be reassured that the condition runs a benign course.

To the Editor:

Figure 1. A 30-cm pink and violaceous, asymmetric, reticulated patch on the lateral aspect of the right thigh.

Figure 2. Histopathology revealed widely dilated vascular channels containing collections of histiocytes in the superficial dermis with adjacent features of chronic lymphedema (A)(H&E, original magnification ×10) as well as a collection of histiocytes in a dilated lymphatic channel (B)(H&E, original magnification ×40). D2-40 staining demonstrated ectatic lymphatic vessels in the upper dermins (C)(original magnification ×20).

A 70-year-old white man presented with an asymptomatic patch on the lateral aspect of the right thigh of 15 months’ duration. The patient believed the patch correlated with a hip replacement 3 years prior; however, it was 6 inches inferior to the incision site. Physical examination revealed a 30-cm pink and violaceous, asymmetric, reticulated patch (Figure 1). The patch was unresponsive to topical corticosteroids as well as a short course of oral prednisone. The patient’s medical history was notable for type 2 diabetes mellitus. Histopathologic examination revealed widely dilated vascular channels containing collections of histiocytes in the superficial dermis. In addition, adjacent features of chronic lymphedema were present, namely interstitial fibroplasia with dilated lymphatic vessels and a lymphoplasmacytic infiltrate (Figure 2). These findings were consistent with intralymphatic histiocytosis, a rare disease most commonly associated with rheumatoid arthritis. Our patient did not have a history or clinical symptoms of rheumatoid arthritis.

Intralymphatic histiocytosis is a rare cutaneous condition reported by O’Grady et al¹ in 1994. This condition has been most frequently associated with rheumatoid arthritis²; however, there has been an emerging association in patients with orthopedic metal implants, with and without a concomitant diagnosis of rheumatoid arthritis. Cases associated with metal implants are rare.^2-7

The condition presents as asymptomatic red, brown, or violaceous patches, plaques, papules, or nodules that are ill defined and tend to demonstrate a livedo reticularis–like pattern. The lesions typically are overlying or in close proximity to a joint. Histopathologic findings include dilated vascular structures in the reticular dermis, some with empty lumina and others containing collections of mononuclear histiocytes. There also may be an inflammatory infiltrate in the adjacent dermis composed of a mix of lymphocytes, plasma cells, and/or histiocytes. Endothelial cells lining the dilated lumina express immunoreactivity for CD31, CD34, D2-40, Lyve-1, and Prox-1. Intravascular histiocytes are positive for CD68 and CD31.⁶

The pathogenesis of intralymphatic histiocytosis remains undefined. Some hypothesize that intralymphatic histiocytosis could be the early stage of reactive angioendotheliomatosis, as these conditions share clinical and histological features.⁸ Reactive angioendotheliomatosis also is a rare condition that may present as erythematous to violaceous patches or plaques. The lesions are commonly found on the limbs and may be associated with constitutional symptoms. Histologic findings of reactive angioendotheliomatosis include a proliferation of epithelioid, round, or spindle-shaped cells within the lumina of dermal blood vessels, which show positivity for CD31 and CD34.⁹ Others suggest the lesions of intralymphatic histiocytosis arise from lymphangiectasia; obstruction of lymphatic drainage due to congenital abnormalities; or acquired damage from infection, trauma, surgery, or radiation.² Due to the common association with rheumatoid arthritis and orthopedic implants, it is likely that lymphatic stasis secondary to chronic inflammation plays a notable role.

Therapies such as topical and systemic corticosteroids, local radiotherapy, cyclophosphamide, pentoxifylline, and arthrocentesis have been attempted without evidence of efficacy.² Although intralymphatic histiocytosis is chronic and resistant to therapy, patients can be reassured that the condition runs a benign course.

To the Editor:
Lichen sclerosus (LS) is a chronic inflammatory disorder of unknown etiology that most commonly affects the anogenital region. Progressive sclerosis results in scarring with distortion of the normal epithelial architecture.^1,2 The lifetime risk for developing squamous cell carcinoma (SCC) as a complication of long-standing LS has been estimated as 4% to 6%.^3,4 However, there is no general agreement concerning the exact relationship between anogenital LS and SCC.¹ The coexistence of histologic findings of LS, vulvar intraepithelial neoplasia (VIN), and SCC in the same tissue is rare. We report a case of VIN and SCC developing in a region of preexisting LS.

A 76-year-old woman presented with a 7-mm nodule on the clitoris that was surrounded by a pearly white, smooth, glistening area (Figure 1). The patient reported pain and tenderness associated with the nodule. No regional lymphadenopathy was evident. We performed an excisional biopsy of the entire nodule and a small part of the whitish patch (Figure 2A). On histologic examination, the presence of hyperkeratosis, epidermal atrophy, a swollen dermal collagen bundle, and prominent edema was consistent with LS (Figure 2B). The presence of dysplastic changes with mild disturbance of the epithelial architecture as well as acanthosis and dyskeratosis in the same tissue confirmed VIN (Figure 2C). Dermal invasion and transition to SCC were seen in the part of the tissue verified as VIN. The presence of dermal tumor nests and an irregular border between the epidermis and dermis pointed to the existence of fully developed SCC (Figure 2D). To prevent the recurrence of SCC, the patient returned for follow-up periodically. There was no recurrence within 6 months after excision.

Figure 2. An excisional biopsy showed epidermal thinning on the left side and invasion of the dermis by a tumor nest on the right side (A)(H&E, original magnification ×10). Left, center, and right boxes indicate areas shown in Figures 2B, 2C and 2D, respectively. Hyperkeratosis, epidermal atrophy, a swollen dermal collagen bundle, and prominent edema was evident (B)(H&E, original magnification ×200). Dysplactic changes with mild disturbance of the epithelial architecture accompanied by acanthosis and nuclear atypia were seen (C)(H&E, original magnification ×200). Irregular masses of atypical squamous cells spread downward into the dermis representing squamous cell carcinoma of a well-differentiated type (D)(H&E, original magnification ×200).

Although LS is considered a premalignant condition, only a small portion of patients with LS ultimately develop vulvar SCC.⁵ There are a number of reasons for linking LS with the development of vulvar SCC. First, in the majority of cases of vulvar SCC, LS, squamous cell hyperplasia, or VIN is present in the adjacent epithelium. Lichen sclerosus is found in adjacent regions in up to 62% of vulvar SCC cases.⁶ Second, patients with LS may develop vulvar SCC, as frequently reported. Third, in a series of LS patients who underwent long-term follow-up, 4% to 6% were reported to have developed vulvar SCC.^3,4,7

Lichen sclerosus is an inflammatory dermatosis characterized by clinicopathologic persistence and hypocellular fibrosis.² Changes in the local environment of the keratinocyte, including chronic inflammation and sclerosis, may be responsible for the promotion of carcinogenesis.⁸ However, no molecular markers have been proven to identify the LS lesions that are at risk for developing into vulvar SCC.^9,10 It has been suggested that VIN is the direct precursor of vulvar SCC.^11,12

Histologic diagnosis of VIN is difficult. Its identification is hindered by a high degree of cellular differentiation combined with the absence of widespread architectural disorder, nuclear pleomorphism, and diffuse nuclear atypia.¹³ The atypia in VIN lesions is strictly confined to the basal and parabasal layers of the epithelium.¹¹ Vulvar intraepithelial neoplasia has seldom been diagnosed as a solitary lesion because it appears to have a short intraepithelial lifetime.

Vulvar SCC can be divided into 2 patterns. The first is found in older women, which is unrelated to human papillomavirus (HPV). This type occurs in a background of LS and/or differentiated VIN. The second is predominantly found in younger women, which is related to high-risk HPV. This type of vulvar SCC frequently is associated with the histologic subtypes of warty and basaloid differentiations and is referred to as undifferentiated VIN. There is no association with LS in these cases.^2,14,15

It has been suggested that LS and HPV may not be mutually exclusive but may act as cofactors in SCC pathogenesis.¹⁶ Infection with HPV is an early event in the multistep process of vulvar carcinogenesis, and HPV integration into host cell genome seems to be related to the progression of vulvar dysplasia.¹⁷ Viral integration generally disrupts the E2 region, resulting in enhanced expression of E6 and E7. E6 and E7 have the ability to bind and inactivate the protein p53 and retinoblastoma protein, which promotes rapid progression through the cell cycle without p53-mediated control of DNA integrity.¹⁸ However, the exact influence of HPV in vulvar SCC is uncertain, as divergent prevalence rates have been published.

In our case, histologic examination revealed the characteristic findings of LS, VIN, and SCC in succession. This sequence is evidence of progressive transition from LS to VIN and then to SCC. Consequently, this case suggests that vulvar LS may act as both an initiator and a promoter of carcinogenesis and that VIN may be the direct precursor of vulvar SCC. In conclusion, LS has a considerable risk for malignant transformation and requires continuous follow-up in all patients. Early histological detection of invasive lesions is crucial to reduce the risk for vulvar cancer.

To the Editor:
Lichen sclerosus (LS) is a chronic inflammatory disorder of unknown etiology that most commonly affects the anogenital region. Progressive sclerosis results in scarring with distortion of the normal epithelial architecture.^1,2 The lifetime risk for developing squamous cell carcinoma (SCC) as a complication of long-standing LS has been estimated as 4% to 6%.^3,4 However, there is no general agreement concerning the exact relationship between anogenital LS and SCC.¹ The coexistence of histologic findings of LS, vulvar intraepithelial neoplasia (VIN), and SCC in the same tissue is rare. We report a case of VIN and SCC developing in a region of preexisting LS.

A 76-year-old woman presented with a 7-mm nodule on the clitoris that was surrounded by a pearly white, smooth, glistening area (Figure 1). The patient reported pain and tenderness associated with the nodule. No regional lymphadenopathy was evident. We performed an excisional biopsy of the entire nodule and a small part of the whitish patch (Figure 2A). On histologic examination, the presence of hyperkeratosis, epidermal atrophy, a swollen dermal collagen bundle, and prominent edema was consistent with LS (Figure 2B). The presence of dysplastic changes with mild disturbance of the epithelial architecture as well as acanthosis and dyskeratosis in the same tissue confirmed VIN (Figure 2C). Dermal invasion and transition to SCC were seen in the part of the tissue verified as VIN. The presence of dermal tumor nests and an irregular border between the epidermis and dermis pointed to the existence of fully developed SCC (Figure 2D). To prevent the recurrence of SCC, the patient returned for follow-up periodically. There was no recurrence within 6 months after excision.

Figure 2. An excisional biopsy showed epidermal thinning on the left side and invasion of the dermis by a tumor nest on the right side (A)(H&E, original magnification ×10). Left, center, and right boxes indicate areas shown in Figures 2B, 2C and 2D, respectively. Hyperkeratosis, epidermal atrophy, a swollen dermal collagen bundle, and prominent edema was evident (B)(H&E, original magnification ×200). Dysplactic changes with mild disturbance of the epithelial architecture accompanied by acanthosis and nuclear atypia were seen (C)(H&E, original magnification ×200). Irregular masses of atypical squamous cells spread downward into the dermis representing squamous cell carcinoma of a well-differentiated type (D)(H&E, original magnification ×200).

Although LS is considered a premalignant condition, only a small portion of patients with LS ultimately develop vulvar SCC.⁵ There are a number of reasons for linking LS with the development of vulvar SCC. First, in the majority of cases of vulvar SCC, LS, squamous cell hyperplasia, or VIN is present in the adjacent epithelium. Lichen sclerosus is found in adjacent regions in up to 62% of vulvar SCC cases.⁶ Second, patients with LS may develop vulvar SCC, as frequently reported. Third, in a series of LS patients who underwent long-term follow-up, 4% to 6% were reported to have developed vulvar SCC.^3,4,7

Lichen sclerosus is an inflammatory dermatosis characterized by clinicopathologic persistence and hypocellular fibrosis.² Changes in the local environment of the keratinocyte, including chronic inflammation and sclerosis, may be responsible for the promotion of carcinogenesis.⁸ However, no molecular markers have been proven to identify the LS lesions that are at risk for developing into vulvar SCC.^9,10 It has been suggested that VIN is the direct precursor of vulvar SCC.^11,12

Histologic diagnosis of VIN is difficult. Its identification is hindered by a high degree of cellular differentiation combined with the absence of widespread architectural disorder, nuclear pleomorphism, and diffuse nuclear atypia.¹³ The atypia in VIN lesions is strictly confined to the basal and parabasal layers of the epithelium.¹¹ Vulvar intraepithelial neoplasia has seldom been diagnosed as a solitary lesion because it appears to have a short intraepithelial lifetime.

Vulvar SCC can be divided into 2 patterns. The first is found in older women, which is unrelated to human papillomavirus (HPV). This type occurs in a background of LS and/or differentiated VIN. The second is predominantly found in younger women, which is related to high-risk HPV. This type of vulvar SCC frequently is associated with the histologic subtypes of warty and basaloid differentiations and is referred to as undifferentiated VIN. There is no association with LS in these cases.^2,14,15

It has been suggested that LS and HPV may not be mutually exclusive but may act as cofactors in SCC pathogenesis.¹⁶ Infection with HPV is an early event in the multistep process of vulvar carcinogenesis, and HPV integration into host cell genome seems to be related to the progression of vulvar dysplasia.¹⁷ Viral integration generally disrupts the E2 region, resulting in enhanced expression of E6 and E7. E6 and E7 have the ability to bind and inactivate the protein p53 and retinoblastoma protein, which promotes rapid progression through the cell cycle without p53-mediated control of DNA integrity.¹⁸ However, the exact influence of HPV in vulvar SCC is uncertain, as divergent prevalence rates have been published.

In our case, histologic examination revealed the characteristic findings of LS, VIN, and SCC in succession. This sequence is evidence of progressive transition from LS to VIN and then to SCC. Consequently, this case suggests that vulvar LS may act as both an initiator and a promoter of carcinogenesis and that VIN may be the direct precursor of vulvar SCC. In conclusion, LS has a considerable risk for malignant transformation and requires continuous follow-up in all patients. Early histological detection of invasive lesions is crucial to reduce the risk for vulvar cancer.

To the Editor:
Lichen sclerosus (LS) is a chronic inflammatory disorder of unknown etiology that most commonly affects the anogenital region. Progressive sclerosis results in scarring with distortion of the normal epithelial architecture.^1,2 The lifetime risk for developing squamous cell carcinoma (SCC) as a complication of long-standing LS has been estimated as 4% to 6%.^3,4 However, there is no general agreement concerning the exact relationship between anogenital LS and SCC.¹ The coexistence of histologic findings of LS, vulvar intraepithelial neoplasia (VIN), and SCC in the same tissue is rare. We report a case of VIN and SCC developing in a region of preexisting LS.

A 76-year-old woman presented with a 7-mm nodule on the clitoris that was surrounded by a pearly white, smooth, glistening area (Figure 1). The patient reported pain and tenderness associated with the nodule. No regional lymphadenopathy was evident. We performed an excisional biopsy of the entire nodule and a small part of the whitish patch (Figure 2A). On histologic examination, the presence of hyperkeratosis, epidermal atrophy, a swollen dermal collagen bundle, and prominent edema was consistent with LS (Figure 2B). The presence of dysplastic changes with mild disturbance of the epithelial architecture as well as acanthosis and dyskeratosis in the same tissue confirmed VIN (Figure 2C). Dermal invasion and transition to SCC were seen in the part of the tissue verified as VIN. The presence of dermal tumor nests and an irregular border between the epidermis and dermis pointed to the existence of fully developed SCC (Figure 2D). To prevent the recurrence of SCC, the patient returned for follow-up periodically. There was no recurrence within 6 months after excision.

Figure 2. An excisional biopsy showed epidermal thinning on the left side and invasion of the dermis by a tumor nest on the right side (A)(H&E, original magnification ×10). Left, center, and right boxes indicate areas shown in Figures 2B, 2C and 2D, respectively. Hyperkeratosis, epidermal atrophy, a swollen dermal collagen bundle, and prominent edema was evident (B)(H&E, original magnification ×200). Dysplactic changes with mild disturbance of the epithelial architecture accompanied by acanthosis and nuclear atypia were seen (C)(H&E, original magnification ×200). Irregular masses of atypical squamous cells spread downward into the dermis representing squamous cell carcinoma of a well-differentiated type (D)(H&E, original magnification ×200).

Although LS is considered a premalignant condition, only a small portion of patients with LS ultimately develop vulvar SCC.⁵ There are a number of reasons for linking LS with the development of vulvar SCC. First, in the majority of cases of vulvar SCC, LS, squamous cell hyperplasia, or VIN is present in the adjacent epithelium. Lichen sclerosus is found in adjacent regions in up to 62% of vulvar SCC cases.⁶ Second, patients with LS may develop vulvar SCC, as frequently reported. Third, in a series of LS patients who underwent long-term follow-up, 4% to 6% were reported to have developed vulvar SCC.^3,4,7

Lichen sclerosus is an inflammatory dermatosis characterized by clinicopathologic persistence and hypocellular fibrosis.² Changes in the local environment of the keratinocyte, including chronic inflammation and sclerosis, may be responsible for the promotion of carcinogenesis.⁸ However, no molecular markers have been proven to identify the LS lesions that are at risk for developing into vulvar SCC.^9,10 It has been suggested that VIN is the direct precursor of vulvar SCC.^11,12

Histologic diagnosis of VIN is difficult. Its identification is hindered by a high degree of cellular differentiation combined with the absence of widespread architectural disorder, nuclear pleomorphism, and diffuse nuclear atypia.¹³ The atypia in VIN lesions is strictly confined to the basal and parabasal layers of the epithelium.¹¹ Vulvar intraepithelial neoplasia has seldom been diagnosed as a solitary lesion because it appears to have a short intraepithelial lifetime.

Vulvar SCC can be divided into 2 patterns. The first is found in older women, which is unrelated to human papillomavirus (HPV). This type occurs in a background of LS and/or differentiated VIN. The second is predominantly found in younger women, which is related to high-risk HPV. This type of vulvar SCC frequently is associated with the histologic subtypes of warty and basaloid differentiations and is referred to as undifferentiated VIN. There is no association with LS in these cases.^2,14,15

It has been suggested that LS and HPV may not be mutually exclusive but may act as cofactors in SCC pathogenesis.¹⁶ Infection with HPV is an early event in the multistep process of vulvar carcinogenesis, and HPV integration into host cell genome seems to be related to the progression of vulvar dysplasia.¹⁷ Viral integration generally disrupts the E2 region, resulting in enhanced expression of E6 and E7. E6 and E7 have the ability to bind and inactivate the protein p53 and retinoblastoma protein, which promotes rapid progression through the cell cycle without p53-mediated control of DNA integrity.¹⁸ However, the exact influence of HPV in vulvar SCC is uncertain, as divergent prevalence rates have been published.

In our case, histologic examination revealed the characteristic findings of LS, VIN, and SCC in succession. This sequence is evidence of progressive transition from LS to VIN and then to SCC. Consequently, this case suggests that vulvar LS may act as both an initiator and a promoter of carcinogenesis and that VIN may be the direct precursor of vulvar SCC. In conclusion, LS has a considerable risk for malignant transformation and requires continuous follow-up in all patients. Early histological detection of invasive lesions is crucial to reduce the risk for vulvar cancer.

The Diagnosis: Congenital Folliculosebaceous Cystic Hamartoma

Folliculosebaceous cystic hamartoma (FSCH) is a rare skin condition that is either congenital or acquired. It presents as a slow-growing and flesh-colored papulonodular lesion¹ that mainly occurs on the head and neck. Involvement of the nipples, perineum, back, forearms, genital areas, and subcutaneous tissue also has been reported but usually indicates a larger lesion.^1,2

Histologically, FSCH is considered a hamartoma composed of both ectodermal and mesodermal elements.¹ Folliculosebaceous cystic hamartoma is a more complex lesion composed of infundibulocystic structures connected to maloriented folliculosebaceous units surrounded by whorls of highly vascularized fibrous stroma and adipocytes. Clefts between fibroepithelial units and surrounding stroma usually are present.¹

Epithelial components contribute to the adnexal and folliculosebaceous cystic proliferations, and mesenchymal elements include vascular tissue, adipose tissue, and fibroblast-rich stroma.^1,2 Acquired lesions arising in adults have been described,^1-5 but the congenital presentation of FSCH in infancy is rare.

Histopathologically, some variations of FSCH are mainly composed of epithelial components while others are composed of nonepithelial components. Nonepithelial components include neural proliferation, muscle components, vascular proliferation, and mucin deposition.^1-4 In some cases, FSCH may coexist with other diseases, such as nevus lipomatosus cutaneous superficialis and neurofibromatosis type I.^4,5

In our case, histopathology showed several dermal infundibulocystic structures that were lined by stratified squamous epithelium and contained horny material (Figure 1). Numerous immature sebaceous lobules and rudimentary hair follicles emanated from some of the cyst walls. Mesenchymal changes around the fibroepithelial units included fibrillary bundles of collagen, clusters of adipocytes, and an increased number of small venules (Figure 2). In addition, the stroma adjacent to the malformed perifollicle contained some amount of mucin. Prominent clefts formed between fibroepithelial units and the surrounding altered stroma.
 

The differential diagnosis mainly includes sebaceous trichofolliculoma, molluscum contagiosum, dermoid cysts, pilomatrixoma, Spitz nevus, and nevus lipomatosus superficialis. The differential diagnosis between FSCH and sebaceous trichofolliculoma is challenging. Both lesions show an infundibular cyst and surrounding sebaceous nodules. According to Plewig,⁶ trichofolliculoma has a wide spectrum ranging from low to high differentiation represented by trichofolliculoma, sebaceous trichofolliculoma, and FSCH, respectively. It is not difficult to distinguish FSCH from other diseases according to its peculiar histopathologic features.

The clinicopathologic features of our case were similar to those of reported FSCH cases, except for the following unique characteristics: congenital lesion, lack of terminal hair, and no sebaceous material extrusion. These features of hair and sebaceous material may be correlated with the patient’s age and hormonal level.¹ Androgen may play a key role in sebaceous gland development at puberty, which leads to sebaceous gland hyperplasia and hypertrophy. Therefore, slight pressure from the lesions can make ivory-white sebaceous material discharge. Hence, the dermatologist and pediatrician must be poised and sensitive while making an initial diagnosis of FSCH.

The Diagnosis: Congenital Folliculosebaceous Cystic Hamartoma

Folliculosebaceous cystic hamartoma (FSCH) is a rare skin condition that is either congenital or acquired. It presents as a slow-growing and flesh-colored papulonodular lesion¹ that mainly occurs on the head and neck. Involvement of the nipples, perineum, back, forearms, genital areas, and subcutaneous tissue also has been reported but usually indicates a larger lesion.^1,2

Histologically, FSCH is considered a hamartoma composed of both ectodermal and mesodermal elements.¹ Folliculosebaceous cystic hamartoma is a more complex lesion composed of infundibulocystic structures connected to maloriented folliculosebaceous units surrounded by whorls of highly vascularized fibrous stroma and adipocytes. Clefts between fibroepithelial units and surrounding stroma usually are present.¹

Epithelial components contribute to the adnexal and folliculosebaceous cystic proliferations, and mesenchymal elements include vascular tissue, adipose tissue, and fibroblast-rich stroma.^1,2 Acquired lesions arising in adults have been described,^1-5 but the congenital presentation of FSCH in infancy is rare.

Histopathologically, some variations of FSCH are mainly composed of epithelial components while others are composed of nonepithelial components. Nonepithelial components include neural proliferation, muscle components, vascular proliferation, and mucin deposition.^1-4 In some cases, FSCH may coexist with other diseases, such as nevus lipomatosus cutaneous superficialis and neurofibromatosis type I.^4,5

In our case, histopathology showed several dermal infundibulocystic structures that were lined by stratified squamous epithelium and contained horny material (Figure 1). Numerous immature sebaceous lobules and rudimentary hair follicles emanated from some of the cyst walls. Mesenchymal changes around the fibroepithelial units included fibrillary bundles of collagen, clusters of adipocytes, and an increased number of small venules (Figure 2). In addition, the stroma adjacent to the malformed perifollicle contained some amount of mucin. Prominent clefts formed between fibroepithelial units and the surrounding altered stroma.
 

The differential diagnosis mainly includes sebaceous trichofolliculoma, molluscum contagiosum, dermoid cysts, pilomatrixoma, Spitz nevus, and nevus lipomatosus superficialis. The differential diagnosis between FSCH and sebaceous trichofolliculoma is challenging. Both lesions show an infundibular cyst and surrounding sebaceous nodules. According to Plewig,⁶ trichofolliculoma has a wide spectrum ranging from low to high differentiation represented by trichofolliculoma, sebaceous trichofolliculoma, and FSCH, respectively. It is not difficult to distinguish FSCH from other diseases according to its peculiar histopathologic features.

The clinicopathologic features of our case were similar to those of reported FSCH cases, except for the following unique characteristics: congenital lesion, lack of terminal hair, and no sebaceous material extrusion. These features of hair and sebaceous material may be correlated with the patient’s age and hormonal level.¹ Androgen may play a key role in sebaceous gland development at puberty, which leads to sebaceous gland hyperplasia and hypertrophy. Therefore, slight pressure from the lesions can make ivory-white sebaceous material discharge. Hence, the dermatologist and pediatrician must be poised and sensitive while making an initial diagnosis of FSCH.

The Diagnosis: Congenital Folliculosebaceous Cystic Hamartoma

Folliculosebaceous cystic hamartoma (FSCH) is a rare skin condition that is either congenital or acquired. It presents as a slow-growing and flesh-colored papulonodular lesion¹ that mainly occurs on the head and neck. Involvement of the nipples, perineum, back, forearms, genital areas, and subcutaneous tissue also has been reported but usually indicates a larger lesion.^1,2

Histologically, FSCH is considered a hamartoma composed of both ectodermal and mesodermal elements.¹ Folliculosebaceous cystic hamartoma is a more complex lesion composed of infundibulocystic structures connected to maloriented folliculosebaceous units surrounded by whorls of highly vascularized fibrous stroma and adipocytes. Clefts between fibroepithelial units and surrounding stroma usually are present.¹

Epithelial components contribute to the adnexal and folliculosebaceous cystic proliferations, and mesenchymal elements include vascular tissue, adipose tissue, and fibroblast-rich stroma.^1,2 Acquired lesions arising in adults have been described,^1-5 but the congenital presentation of FSCH in infancy is rare.

Histopathologically, some variations of FSCH are mainly composed of epithelial components while others are composed of nonepithelial components. Nonepithelial components include neural proliferation, muscle components, vascular proliferation, and mucin deposition.^1-4 In some cases, FSCH may coexist with other diseases, such as nevus lipomatosus cutaneous superficialis and neurofibromatosis type I.^4,5

In our case, histopathology showed several dermal infundibulocystic structures that were lined by stratified squamous epithelium and contained horny material (Figure 1). Numerous immature sebaceous lobules and rudimentary hair follicles emanated from some of the cyst walls. Mesenchymal changes around the fibroepithelial units included fibrillary bundles of collagen, clusters of adipocytes, and an increased number of small venules (Figure 2). In addition, the stroma adjacent to the malformed perifollicle contained some amount of mucin. Prominent clefts formed between fibroepithelial units and the surrounding altered stroma.
 

The differential diagnosis mainly includes sebaceous trichofolliculoma, molluscum contagiosum, dermoid cysts, pilomatrixoma, Spitz nevus, and nevus lipomatosus superficialis. The differential diagnosis between FSCH and sebaceous trichofolliculoma is challenging. Both lesions show an infundibular cyst and surrounding sebaceous nodules. According to Plewig,⁶ trichofolliculoma has a wide spectrum ranging from low to high differentiation represented by trichofolliculoma, sebaceous trichofolliculoma, and FSCH, respectively. It is not difficult to distinguish FSCH from other diseases according to its peculiar histopathologic features.

The clinicopathologic features of our case were similar to those of reported FSCH cases, except for the following unique characteristics: congenital lesion, lack of terminal hair, and no sebaceous material extrusion. These features of hair and sebaceous material may be correlated with the patient’s age and hormonal level.¹ Androgen may play a key role in sebaceous gland development at puberty, which leads to sebaceous gland hyperplasia and hypertrophy. Therefore, slight pressure from the lesions can make ivory-white sebaceous material discharge. Hence, the dermatologist and pediatrician must be poised and sensitive while making an initial diagnosis of FSCH.

Practice Gap

Warts may negatively impact a patient's quality of life, as they may cause not only discomfort and pain but also embarrassment and low self-esteem.¹ Moreover, Ciconte et al¹ demonstrated that study participants with warts on their feet were more likely to report physical discomfort than those with warts on their hands. Therefore, plantar warts should be diagnosed promptly to allow for proper treatment.

Warts may be identified by viewing the dilated capillaries that lie on their surface, which appear as small black dots to the naked eye.¹ The formation of a plantar wart obliterates the normal plantar creases, thereby flattening the skin’s natural markings. However, a plantar wart may appear clinically similar to a callus and both lesions typically form in pressure point areas, warranting the use of a tool that aids in its diagnostic evaluation.^1,2

Diagnostic Tools

Dermoscopy, a noninvasive tool that creates a microscopic visualization of lesions, is commonly used to distinguish dermatologic pathology if the clinical presentation overlaps with a similar lesion, such as a callus, corn, or plantar wart.^1,3 However, there is another way of differentiating plantar warts from calluses using a simple 2-step clinical maneuver that we learned from Dr. Lewis Kaplan at the University of Miami.

Using the thumb or index finger, apply pressure at a perpendicular angle to the lesion on the sole of the patient’s foot, which will not create substantial discomfort or pain in a patient who has a plantar wart (Figure) but will be painful in a patient who has a callus due to the underlying bony spur. The next step involves applying pressure to the left and right sides of the lesion by squeezing toward the center with the thumb and index finger at a 45° angle. This maneuver will create substantial discomfort and pain in patients with plantar warts, thus helping to confirm the diagnosis.

A plantar wart before (A) and after undergoing the squeeze maneuver (B). The patient denied feelings of discomfort or pain.

Practice Implications

Rarely, a plantar wart can progress to form a verrucous carcinoma if left untreated.² Thus, it is important to diagnose and treat plantar warts to avoid pain and potential complications. The technique discussed here, which we are coining as the “squeeze maneuver,” allows for easy diagnosis and negates the need for an expensive diagnostic tool.To submit a clinical pearl, contact our Editorial Office.

Practice Gap

Warts may negatively impact a patient's quality of life, as they may cause not only discomfort and pain but also embarrassment and low self-esteem.¹ Moreover, Ciconte et al¹ demonstrated that study participants with warts on their feet were more likely to report physical discomfort than those with warts on their hands. Therefore, plantar warts should be diagnosed promptly to allow for proper treatment.

Warts may be identified by viewing the dilated capillaries that lie on their surface, which appear as small black dots to the naked eye.¹ The formation of a plantar wart obliterates the normal plantar creases, thereby flattening the skin’s natural markings. However, a plantar wart may appear clinically similar to a callus and both lesions typically form in pressure point areas, warranting the use of a tool that aids in its diagnostic evaluation.^1,2

Diagnostic Tools

Dermoscopy, a noninvasive tool that creates a microscopic visualization of lesions, is commonly used to distinguish dermatologic pathology if the clinical presentation overlaps with a similar lesion, such as a callus, corn, or plantar wart.^1,3 However, there is another way of differentiating plantar warts from calluses using a simple 2-step clinical maneuver that we learned from Dr. Lewis Kaplan at the University of Miami.

Using the thumb or index finger, apply pressure at a perpendicular angle to the lesion on the sole of the patient’s foot, which will not create substantial discomfort or pain in a patient who has a plantar wart (Figure) but will be painful in a patient who has a callus due to the underlying bony spur. The next step involves applying pressure to the left and right sides of the lesion by squeezing toward the center with the thumb and index finger at a 45° angle. This maneuver will create substantial discomfort and pain in patients with plantar warts, thus helping to confirm the diagnosis.

A plantar wart before (A) and after undergoing the squeeze maneuver (B). The patient denied feelings of discomfort or pain.

Practice Implications

Rarely, a plantar wart can progress to form a verrucous carcinoma if left untreated.² Thus, it is important to diagnose and treat plantar warts to avoid pain and potential complications. The technique discussed here, which we are coining as the “squeeze maneuver,” allows for easy diagnosis and negates the need for an expensive diagnostic tool.To submit a clinical pearl, contact our Editorial Office.

Practice Gap

Warts may negatively impact a patient's quality of life, as they may cause not only discomfort and pain but also embarrassment and low self-esteem.¹ Moreover, Ciconte et al¹ demonstrated that study participants with warts on their feet were more likely to report physical discomfort than those with warts on their hands. Therefore, plantar warts should be diagnosed promptly to allow for proper treatment.

Warts may be identified by viewing the dilated capillaries that lie on their surface, which appear as small black dots to the naked eye.¹ The formation of a plantar wart obliterates the normal plantar creases, thereby flattening the skin’s natural markings. However, a plantar wart may appear clinically similar to a callus and both lesions typically form in pressure point areas, warranting the use of a tool that aids in its diagnostic evaluation.^1,2

Diagnostic Tools

Dermoscopy, a noninvasive tool that creates a microscopic visualization of lesions, is commonly used to distinguish dermatologic pathology if the clinical presentation overlaps with a similar lesion, such as a callus, corn, or plantar wart.^1,3 However, there is another way of differentiating plantar warts from calluses using a simple 2-step clinical maneuver that we learned from Dr. Lewis Kaplan at the University of Miami.

Using the thumb or index finger, apply pressure at a perpendicular angle to the lesion on the sole of the patient’s foot, which will not create substantial discomfort or pain in a patient who has a plantar wart (Figure) but will be painful in a patient who has a callus due to the underlying bony spur. The next step involves applying pressure to the left and right sides of the lesion by squeezing toward the center with the thumb and index finger at a 45° angle. This maneuver will create substantial discomfort and pain in patients with plantar warts, thus helping to confirm the diagnosis.

A plantar wart before (A) and after undergoing the squeeze maneuver (B). The patient denied feelings of discomfort or pain.

Practice Implications

Rarely, a plantar wart can progress to form a verrucous carcinoma if left untreated.² Thus, it is important to diagnose and treat plantar warts to avoid pain and potential complications. The technique discussed here, which we are coining as the “squeeze maneuver,” allows for easy diagnosis and negates the need for an expensive diagnostic tool.To submit a clinical pearl, contact our Editorial Office.

Porokeratosis of Mibelli (PM) is a lesion characterized by a surrounding cornoid lamella with variable nonspecific findings (eg, atrophy, acanthosis, verrucous hyperplasia) in the center of the lesion that typically presents in infancy to early childhood.¹ We report a case of PM in which a prior biopsy from the center of the lesion demonstrated papulosquamous dermatitis. We propose a 3-step technique to ensure proper orientation of a punch biopsy in cases of suspected PM.

Case Report

A 3-year-old girl presented with an erythematous, hypopigmented, scaling plaque on the posterior aspect of the left ankle surrounded by a hard rim. The plaque was first noted at 12 months of age and had slowly enlarged as the patient grew. Six months prior, a biopsy from the center of the lesion performed at another facility demonstrated a papulosquamous dermatitis.

Physical examination revealed a lesion that was 4.2-cm long, 2.2-cm wide at the superior pole, and 3.5-cm wide at the inferior pole (Figure 1). A line was drawn with a skin marker perpendicular to the rim of the lesion (Figure 2A) and a 6-mm punch biopsy was performed, centered at the intersection of the drawn line and the cornoid lamella (Figure 2B). The tissue was then bisected at the bedside along the skin marker line with a #15 blade (Figure 2C) and submitted in formalin for histologic processing. Histologic examination revealed an invagination of the epidermis producing a tier of parakeratotic cells with its apex pointed away from the center of the lesion. Dyskeratotic cells were noted at the base of the parakeratosis (Figure 3). Verrucous hyperplasia was present in the central portion of the specimen adjacent to the cornoid lamella. Based on these histopathologic findings, the correct diagnosis of PM was made.

Comment

Porokeratosis of Mibelli is a rare condition that typically presents in infancy to early childhood.¹ It may appear as small keratotic papules or larger plaques that reach several centimeters in diameter.² There is a 7.5% risk for malignant transformation (eg, basal cell carcinoma, squamous cell carcinoma, Bowen disease).³ Variable nonspecific findings (eg, atrophy, acanthosis, verrucous hyperplasia) typically are present in the center of the lesion. In our case, a biopsy from the center of the plaque demonstrated verrucous hyperplasia. The incorrect diagnosis of PM as psoriasis also has been reported.⁴

We propose a 3-step technique to ensure proper orientation of a punch biopsy in cases of suspected PM. First, draw a line perpendicular to the rim of the lesion to mark the biopsy site (Figure 2A). Second, perform a punch biopsy centered at the intersection of the drawn line and the cornoid lamella (Figure 2B). Third, section the biopsied tissue with a #15 blade along the perpendicular line at the bedside (Figure 2C). The surgical pathology requisition should mention that the specimen has been transected and the cut edges should be placed down in the cassette, ensuring that the cornoid lamella will be present in cross-section on the slides.

If the punch biopsy specimen is not bisected, it can be difficult to orient it in the pathology laboratory, especially if the cornoid lamellae are not prominent. Furthermore, the technician processing the tissue may not be aware of the importance of sectioning the specimen perpendicular to the cornoid lamella. Following this procedure, diagnosis can be confirmed in virtually every case of PM.

Porokeratosis of Mibelli (PM) is a lesion characterized by a surrounding cornoid lamella with variable nonspecific findings (eg, atrophy, acanthosis, verrucous hyperplasia) in the center of the lesion that typically presents in infancy to early childhood.¹ We report a case of PM in which a prior biopsy from the center of the lesion demonstrated papulosquamous dermatitis. We propose a 3-step technique to ensure proper orientation of a punch biopsy in cases of suspected PM.

Case Report

A 3-year-old girl presented with an erythematous, hypopigmented, scaling plaque on the posterior aspect of the left ankle surrounded by a hard rim. The plaque was first noted at 12 months of age and had slowly enlarged as the patient grew. Six months prior, a biopsy from the center of the lesion performed at another facility demonstrated a papulosquamous dermatitis.

Physical examination revealed a lesion that was 4.2-cm long, 2.2-cm wide at the superior pole, and 3.5-cm wide at the inferior pole (Figure 1). A line was drawn with a skin marker perpendicular to the rim of the lesion (Figure 2A) and a 6-mm punch biopsy was performed, centered at the intersection of the drawn line and the cornoid lamella (Figure 2B). The tissue was then bisected at the bedside along the skin marker line with a #15 blade (Figure 2C) and submitted in formalin for histologic processing. Histologic examination revealed an invagination of the epidermis producing a tier of parakeratotic cells with its apex pointed away from the center of the lesion. Dyskeratotic cells were noted at the base of the parakeratosis (Figure 3). Verrucous hyperplasia was present in the central portion of the specimen adjacent to the cornoid lamella. Based on these histopathologic findings, the correct diagnosis of PM was made.

Comment

Porokeratosis of Mibelli is a rare condition that typically presents in infancy to early childhood.¹ It may appear as small keratotic papules or larger plaques that reach several centimeters in diameter.² There is a 7.5% risk for malignant transformation (eg, basal cell carcinoma, squamous cell carcinoma, Bowen disease).³ Variable nonspecific findings (eg, atrophy, acanthosis, verrucous hyperplasia) typically are present in the center of the lesion. In our case, a biopsy from the center of the plaque demonstrated verrucous hyperplasia. The incorrect diagnosis of PM as psoriasis also has been reported.⁴

We propose a 3-step technique to ensure proper orientation of a punch biopsy in cases of suspected PM. First, draw a line perpendicular to the rim of the lesion to mark the biopsy site (Figure 2A). Second, perform a punch biopsy centered at the intersection of the drawn line and the cornoid lamella (Figure 2B). Third, section the biopsied tissue with a #15 blade along the perpendicular line at the bedside (Figure 2C). The surgical pathology requisition should mention that the specimen has been transected and the cut edges should be placed down in the cassette, ensuring that the cornoid lamella will be present in cross-section on the slides.

If the punch biopsy specimen is not bisected, it can be difficult to orient it in the pathology laboratory, especially if the cornoid lamellae are not prominent. Furthermore, the technician processing the tissue may not be aware of the importance of sectioning the specimen perpendicular to the cornoid lamella. Following this procedure, diagnosis can be confirmed in virtually every case of PM.

Porokeratosis of Mibelli (PM) is a lesion characterized by a surrounding cornoid lamella with variable nonspecific findings (eg, atrophy, acanthosis, verrucous hyperplasia) in the center of the lesion that typically presents in infancy to early childhood.¹ We report a case of PM in which a prior biopsy from the center of the lesion demonstrated papulosquamous dermatitis. We propose a 3-step technique to ensure proper orientation of a punch biopsy in cases of suspected PM.

Case Report

A 3-year-old girl presented with an erythematous, hypopigmented, scaling plaque on the posterior aspect of the left ankle surrounded by a hard rim. The plaque was first noted at 12 months of age and had slowly enlarged as the patient grew. Six months prior, a biopsy from the center of the lesion performed at another facility demonstrated a papulosquamous dermatitis.

Physical examination revealed a lesion that was 4.2-cm long, 2.2-cm wide at the superior pole, and 3.5-cm wide at the inferior pole (Figure 1). A line was drawn with a skin marker perpendicular to the rim of the lesion (Figure 2A) and a 6-mm punch biopsy was performed, centered at the intersection of the drawn line and the cornoid lamella (Figure 2B). The tissue was then bisected at the bedside along the skin marker line with a #15 blade (Figure 2C) and submitted in formalin for histologic processing. Histologic examination revealed an invagination of the epidermis producing a tier of parakeratotic cells with its apex pointed away from the center of the lesion. Dyskeratotic cells were noted at the base of the parakeratosis (Figure 3). Verrucous hyperplasia was present in the central portion of the specimen adjacent to the cornoid lamella. Based on these histopathologic findings, the correct diagnosis of PM was made.

Comment

Porokeratosis of Mibelli is a rare condition that typically presents in infancy to early childhood.¹ It may appear as small keratotic papules or larger plaques that reach several centimeters in diameter.² There is a 7.5% risk for malignant transformation (eg, basal cell carcinoma, squamous cell carcinoma, Bowen disease).³ Variable nonspecific findings (eg, atrophy, acanthosis, verrucous hyperplasia) typically are present in the center of the lesion. In our case, a biopsy from the center of the plaque demonstrated verrucous hyperplasia. The incorrect diagnosis of PM as psoriasis also has been reported.⁴

We propose a 3-step technique to ensure proper orientation of a punch biopsy in cases of suspected PM. First, draw a line perpendicular to the rim of the lesion to mark the biopsy site (Figure 2A). Second, perform a punch biopsy centered at the intersection of the drawn line and the cornoid lamella (Figure 2B). Third, section the biopsied tissue with a #15 blade along the perpendicular line at the bedside (Figure 2C). The surgical pathology requisition should mention that the specimen has been transected and the cut edges should be placed down in the cassette, ensuring that the cornoid lamella will be present in cross-section on the slides.

If the punch biopsy specimen is not bisected, it can be difficult to orient it in the pathology laboratory, especially if the cornoid lamellae are not prominent. Furthermore, the technician processing the tissue may not be aware of the importance of sectioning the specimen perpendicular to the cornoid lamella. Following this procedure, diagnosis can be confirmed in virtually every case of PM.

The best diagnosis is:

a. granular cell tumor
b. intradermal nevus
c. Langerhans cell disease
d. mastocytosis
e. multicentric reticulohistiocytosis

Monomorphic cell infiltrate in the upper dermis (H&E, original magnification ×100).

A closer view reveals cuboidal or spindle cells with basal hyperpigmentation (H&E, original magnification ×200).

Continue to the next page for the diagnosis >>

Mastocytosis

Mastocytosis is a clonal proliferation of mast cells in the skin and various systems of the body including the bone marrow, liver, lymph nodes, and gastrointestinal tract.^1,2 Mast cell proliferation is closely associated with germline and acquired activating KIT mutations.^3-5 Adult-onset mastocytosis is likely to involve several organs, whereas pediatric mastocytosis usually affects only the skin and is self-limiting. Patients with profound mast cell infiltration in the skin or other organs are likely to have attacks of flushing, palpitation, or diarrhea resulting from the degranulation of mast cells and release of histamine.^6,7 In a majority of patients with advanced systemic mastocytosis, mast cells are positive for the Ki-1 antigen (CD30), whereas in most patients with indolent systemic mastocytosis, only a few mast cells are positive for CD30.⁸ Recently, CD30 was reported as a new drug target in patients with CD30⁺ advanced systemic mastocytosis.⁹ Because the skin frequently is involved and easily accessible in comparison with other organs, skin biopsy often is performed to establish a diagnosis of mastocytosis. Cutaneous mastocytosis comprises urticaria pigmentosa, solitary mastocytoma, diffuse cutaneous mastocytosis, and telangiectasia macularis eruptiva perstans; approximately 80% of all cases have urticaria pigmentosa.^10-12 In cutaneous mastocytosis, skin biopsy typically shows monomorphous mast cell infiltrate mostly in the upper third of the dermis. The density of mast cells varies according to the clinical variant. For example, a lesion of telangiectasia macularis eruptiva perstans has only a perivascular mast cell infiltrate, whereas a solitary mastocytoma has sheets of mast cells in the dermis, sometimes extending into the subcutis. A skin biopsy of the brown macule on the waist showed a number of cuboidal or spindle mast cells in the upper dermis with occasional eosinophils. These mast cells are monomorphous, and no mitotic figures, necrotic cells, or atypical cells are seen. Mast cells have metachromatic granules in the cytoplasm, which can be seen with toluidine blue or Giemsa stain. CD117 (c-kit) also is positive. Mast cells in urticaria pigmentosa easily may be mistaken for nevus cells. Hyperpigmentation of the basal layer, a characteristic feature seen in urticaria pigmentosa, also may erroneously suggest a diagnosis of a melanocytic nevus.

Granular cell tumors predominantly affect the oral cavity, but the skin also can be involved. It comprises a fascicular infiltrate of large and polygonal cells with characteristic eosinophilic granular cytoplasm in the dermis (Figure 1).¹³ Cell membranes are not always distinct. Although the nuclei usually are small and centrally located, irregular and plump nuclei with distinct nucleoli also may be seen. The overlying epidermis tends to be hyperplastic. Granular cell tumor is considered a group of lesions of varying histogenesis. Cases in which tumors originated from a neural crest–derived peripheral nerve–related cell as well as a Schwann cell have been reported.^14,15 The origin of granular cell tumors is controversial.

Figure 1. Granular cell tumor showing fascicles of large and polygonal cells with characteristic eosinophilic granular cytoplasm in the dermis (H&E, original magnification ×200).

Figure 2. Intradermal nevus showing nests with melanin in the uppermost area of the lesion and neurotized nevus cells in the lower part (H&E, original magnification ×100). Pseudovascular spaces are seen on the right side.

Intradermal nevus usually has nests and cords of nevus cells in the upper dermis. The uppermost melanocytes often contain a moderate amount of melanin, whereas nevus cells in the mid and lower dermis usually do not contain melanin (Figure 2). Shrinkage during tissue processing maycause clefts between nevus cells, resulting in pseudovascular spaces.¹⁶ The deeper dermis may have a neuroid appearance with spindle-shaped cells and Meissner corpuscle–like structures.¹⁷

Although Langerhans cell disease was formerly known as Langerhans cell histiocytosis and subdivided into several clinical subtypes, including Letterer-Siwe disease, Hand-Schüller-Christian disease, and eosinophilic granuloma, these clinical subtypes commonly overlapped. Langerhans cell disease is now used as a terminology that encompasses all subtypes.^18,19 Langerhans cell disease is characterized by a proliferation of Langerhans cells with a variable mixture of other inflammatory cells. The constituent cells are large and ovoid with a distinct folded or lobulated, often kidney-shaped nucleus.²⁰ Langerhans cells usually infiltrate the upper dermis and occasionally the epidermis (Figure 3). CD1a, HLA-DR, S-100 protein, and langerin are positive in Langerhans cells.²¹

Figure 3. Langerhans cell disease showing an infiltrate of large and ovoid Langerhans cells with a distinct folded or lobulated, often kidney-shaped nucleus in the upper dermis and epidermis (H&E, original magnification ×200).

Figure 4. Multicentric reticulohistiocytosis showing a mixture of mononuclear and multinucleate histiocytes with abundant eosinophilic and finely granular cytoplasm (H&E, original magnification ×200).

Multicentric reticulohistiocytosis is characterized by a combination of papulonodular cutaneous lesions and severe arthropathy.²² An irregular mixture of mononuclear and multinucleate histiocytes showing abundant eosinophilic and finely granular cytoplasm, often with a ground-glass appearance, is seen along with lymphocytic infiltration (Figure 4).²³ A few giant cells may be seen in early lesions; older lesions more commonly have giant cells and fibrosis.

The best diagnosis is:

a. granular cell tumor
b. intradermal nevus
c. Langerhans cell disease
d. mastocytosis
e. multicentric reticulohistiocytosis

Monomorphic cell infiltrate in the upper dermis (H&E, original magnification ×100).

A closer view reveals cuboidal or spindle cells with basal hyperpigmentation (H&E, original magnification ×200).

Continue to the next page for the diagnosis >>

Mastocytosis

Mastocytosis is a clonal proliferation of mast cells in the skin and various systems of the body including the bone marrow, liver, lymph nodes, and gastrointestinal tract.^1,2 Mast cell proliferation is closely associated with germline and acquired activating KIT mutations.^3-5 Adult-onset mastocytosis is likely to involve several organs, whereas pediatric mastocytosis usually affects only the skin and is self-limiting. Patients with profound mast cell infiltration in the skin or other organs are likely to have attacks of flushing, palpitation, or diarrhea resulting from the degranulation of mast cells and release of histamine.^6,7 In a majority of patients with advanced systemic mastocytosis, mast cells are positive for the Ki-1 antigen (CD30), whereas in most patients with indolent systemic mastocytosis, only a few mast cells are positive for CD30.⁸ Recently, CD30 was reported as a new drug target in patients with CD30⁺ advanced systemic mastocytosis.⁹ Because the skin frequently is involved and easily accessible in comparison with other organs, skin biopsy often is performed to establish a diagnosis of mastocytosis. Cutaneous mastocytosis comprises urticaria pigmentosa, solitary mastocytoma, diffuse cutaneous mastocytosis, and telangiectasia macularis eruptiva perstans; approximately 80% of all cases have urticaria pigmentosa.^10-12 In cutaneous mastocytosis, skin biopsy typically shows monomorphous mast cell infiltrate mostly in the upper third of the dermis. The density of mast cells varies according to the clinical variant. For example, a lesion of telangiectasia macularis eruptiva perstans has only a perivascular mast cell infiltrate, whereas a solitary mastocytoma has sheets of mast cells in the dermis, sometimes extending into the subcutis. A skin biopsy of the brown macule on the waist showed a number of cuboidal or spindle mast cells in the upper dermis with occasional eosinophils. These mast cells are monomorphous, and no mitotic figures, necrotic cells, or atypical cells are seen. Mast cells have metachromatic granules in the cytoplasm, which can be seen with toluidine blue or Giemsa stain. CD117 (c-kit) also is positive. Mast cells in urticaria pigmentosa easily may be mistaken for nevus cells. Hyperpigmentation of the basal layer, a characteristic feature seen in urticaria pigmentosa, also may erroneously suggest a diagnosis of a melanocytic nevus.

Granular cell tumors predominantly affect the oral cavity, but the skin also can be involved. It comprises a fascicular infiltrate of large and polygonal cells with characteristic eosinophilic granular cytoplasm in the dermis (Figure 1).¹³ Cell membranes are not always distinct. Although the nuclei usually are small and centrally located, irregular and plump nuclei with distinct nucleoli also may be seen. The overlying epidermis tends to be hyperplastic. Granular cell tumor is considered a group of lesions of varying histogenesis. Cases in which tumors originated from a neural crest–derived peripheral nerve–related cell as well as a Schwann cell have been reported.^14,15 The origin of granular cell tumors is controversial.

Figure 1. Granular cell tumor showing fascicles of large and polygonal cells with characteristic eosinophilic granular cytoplasm in the dermis (H&E, original magnification ×200).

Figure 2. Intradermal nevus showing nests with melanin in the uppermost area of the lesion and neurotized nevus cells in the lower part (H&E, original magnification ×100). Pseudovascular spaces are seen on the right side.

Intradermal nevus usually has nests and cords of nevus cells in the upper dermis. The uppermost melanocytes often contain a moderate amount of melanin, whereas nevus cells in the mid and lower dermis usually do not contain melanin (Figure 2). Shrinkage during tissue processing maycause clefts between nevus cells, resulting in pseudovascular spaces.¹⁶ The deeper dermis may have a neuroid appearance with spindle-shaped cells and Meissner corpuscle–like structures.¹⁷

Although Langerhans cell disease was formerly known as Langerhans cell histiocytosis and subdivided into several clinical subtypes, including Letterer-Siwe disease, Hand-Schüller-Christian disease, and eosinophilic granuloma, these clinical subtypes commonly overlapped. Langerhans cell disease is now used as a terminology that encompasses all subtypes.^18,19 Langerhans cell disease is characterized by a proliferation of Langerhans cells with a variable mixture of other inflammatory cells. The constituent cells are large and ovoid with a distinct folded or lobulated, often kidney-shaped nucleus.²⁰ Langerhans cells usually infiltrate the upper dermis and occasionally the epidermis (Figure 3). CD1a, HLA-DR, S-100 protein, and langerin are positive in Langerhans cells.²¹

Figure 3. Langerhans cell disease showing an infiltrate of large and ovoid Langerhans cells with a distinct folded or lobulated, often kidney-shaped nucleus in the upper dermis and epidermis (H&E, original magnification ×200).

Figure 4. Multicentric reticulohistiocytosis showing a mixture of mononuclear and multinucleate histiocytes with abundant eosinophilic and finely granular cytoplasm (H&E, original magnification ×200).

Multicentric reticulohistiocytosis is characterized by a combination of papulonodular cutaneous lesions and severe arthropathy.²² An irregular mixture of mononuclear and multinucleate histiocytes showing abundant eosinophilic and finely granular cytoplasm, often with a ground-glass appearance, is seen along with lymphocytic infiltration (Figure 4).²³ A few giant cells may be seen in early lesions; older lesions more commonly have giant cells and fibrosis.

The best diagnosis is:

a. granular cell tumor
b. intradermal nevus
c. Langerhans cell disease
d. mastocytosis
e. multicentric reticulohistiocytosis

Monomorphic cell infiltrate in the upper dermis (H&E, original magnification ×100).

A closer view reveals cuboidal or spindle cells with basal hyperpigmentation (H&E, original magnification ×200).

Continue to the next page for the diagnosis >>

Mastocytosis

Mastocytosis is a clonal proliferation of mast cells in the skin and various systems of the body including the bone marrow, liver, lymph nodes, and gastrointestinal tract.^1,2 Mast cell proliferation is closely associated with germline and acquired activating KIT mutations.^3-5 Adult-onset mastocytosis is likely to involve several organs, whereas pediatric mastocytosis usually affects only the skin and is self-limiting. Patients with profound mast cell infiltration in the skin or other organs are likely to have attacks of flushing, palpitation, or diarrhea resulting from the degranulation of mast cells and release of histamine.^6,7 In a majority of patients with advanced systemic mastocytosis, mast cells are positive for the Ki-1 antigen (CD30), whereas in most patients with indolent systemic mastocytosis, only a few mast cells are positive for CD30.⁸ Recently, CD30 was reported as a new drug target in patients with CD30⁺ advanced systemic mastocytosis.⁹ Because the skin frequently is involved and easily accessible in comparison with other organs, skin biopsy often is performed to establish a diagnosis of mastocytosis. Cutaneous mastocytosis comprises urticaria pigmentosa, solitary mastocytoma, diffuse cutaneous mastocytosis, and telangiectasia macularis eruptiva perstans; approximately 80% of all cases have urticaria pigmentosa.^10-12 In cutaneous mastocytosis, skin biopsy typically shows monomorphous mast cell infiltrate mostly in the upper third of the dermis. The density of mast cells varies according to the clinical variant. For example, a lesion of telangiectasia macularis eruptiva perstans has only a perivascular mast cell infiltrate, whereas a solitary mastocytoma has sheets of mast cells in the dermis, sometimes extending into the subcutis. A skin biopsy of the brown macule on the waist showed a number of cuboidal or spindle mast cells in the upper dermis with occasional eosinophils. These mast cells are monomorphous, and no mitotic figures, necrotic cells, or atypical cells are seen. Mast cells have metachromatic granules in the cytoplasm, which can be seen with toluidine blue or Giemsa stain. CD117 (c-kit) also is positive. Mast cells in urticaria pigmentosa easily may be mistaken for nevus cells. Hyperpigmentation of the basal layer, a characteristic feature seen in urticaria pigmentosa, also may erroneously suggest a diagnosis of a melanocytic nevus.

Granular cell tumors predominantly affect the oral cavity, but the skin also can be involved. It comprises a fascicular infiltrate of large and polygonal cells with characteristic eosinophilic granular cytoplasm in the dermis (Figure 1).¹³ Cell membranes are not always distinct. Although the nuclei usually are small and centrally located, irregular and plump nuclei with distinct nucleoli also may be seen. The overlying epidermis tends to be hyperplastic. Granular cell tumor is considered a group of lesions of varying histogenesis. Cases in which tumors originated from a neural crest–derived peripheral nerve–related cell as well as a Schwann cell have been reported.^14,15 The origin of granular cell tumors is controversial.

Figure 1. Granular cell tumor showing fascicles of large and polygonal cells with characteristic eosinophilic granular cytoplasm in the dermis (H&E, original magnification ×200).

Figure 2. Intradermal nevus showing nests with melanin in the uppermost area of the lesion and neurotized nevus cells in the lower part (H&E, original magnification ×100). Pseudovascular spaces are seen on the right side.

Intradermal nevus usually has nests and cords of nevus cells in the upper dermis. The uppermost melanocytes often contain a moderate amount of melanin, whereas nevus cells in the mid and lower dermis usually do not contain melanin (Figure 2). Shrinkage during tissue processing maycause clefts between nevus cells, resulting in pseudovascular spaces.¹⁶ The deeper dermis may have a neuroid appearance with spindle-shaped cells and Meissner corpuscle–like structures.¹⁷

Although Langerhans cell disease was formerly known as Langerhans cell histiocytosis and subdivided into several clinical subtypes, including Letterer-Siwe disease, Hand-Schüller-Christian disease, and eosinophilic granuloma, these clinical subtypes commonly overlapped. Langerhans cell disease is now used as a terminology that encompasses all subtypes.^18,19 Langerhans cell disease is characterized by a proliferation of Langerhans cells with a variable mixture of other inflammatory cells. The constituent cells are large and ovoid with a distinct folded or lobulated, often kidney-shaped nucleus.²⁰ Langerhans cells usually infiltrate the upper dermis and occasionally the epidermis (Figure 3). CD1a, HLA-DR, S-100 protein, and langerin are positive in Langerhans cells.²¹

Figure 3. Langerhans cell disease showing an infiltrate of large and ovoid Langerhans cells with a distinct folded or lobulated, often kidney-shaped nucleus in the upper dermis and epidermis (H&E, original magnification ×200).

Figure 4. Multicentric reticulohistiocytosis showing a mixture of mononuclear and multinucleate histiocytes with abundant eosinophilic and finely granular cytoplasm (H&E, original magnification ×200).

Multicentric reticulohistiocytosis is characterized by a combination of papulonodular cutaneous lesions and severe arthropathy.²² An irregular mixture of mononuclear and multinucleate histiocytes showing abundant eosinophilic and finely granular cytoplasm, often with a ground-glass appearance, is seen along with lymphocytic infiltration (Figure 4).²³ A few giant cells may be seen in early lesions; older lesions more commonly have giant cells and fibrosis.

The Diagnosis: Bilateral Auricular Tophaceous Gout

Histopathologic evaluation with hematoxylin and eosin staining demonstrated clusters of abundant granular amorphous material within the subcutaneous tissue (Figure 1). The overlying epidermis and dermis were unremarkable. The granular amorphous material demonstrated numerous monosodium urate crystals under polarized light (Figure 2). At a return visit following the biopsy results, the patient reported a history of a single episode of monoarticular gouty arthritis involving the right hallux approximately 6 months after the onset of the skin lesions. With the added clinical history and the biopsy results, his serum uric acid level was obtained and was found to be elevated at 9.2 mg/dL (reference range, 3.5–8 mg/dL).

In our patient, the clinical differential diagnosis included calcium deposits, weathering nodules, and tophaceous gout. The differential diagnosis of auricular lesions is broad, and benign lesions may mimic cancerous entities such as basal cell carcinoma and squamous cell carcinoma.¹ Therefore a detailed history, thorough physical examination, and tissue sampling are key to establishing the correct diagnosis. Our patient’s history of monoarticular gouty arthritis was only elucidated after a diagnosis of bilateral auricular tophaceous gout was made based on the biopsy results.

Subcutaneous tophi represent a chronic state of hyperuricemia and tend to manifest after long-standing polyarthritis and repeated acute gout attacks.^2-5 These lesions develop in approximately 50% of gout patients and usually occur an average of 11.6 years after the onset of disease.² There is a subset of individuals that are at higher risk for developing tophi, including elderly and female patients, diuretic and chronic nonsteroidal anti-inflammatory drug users, patients with a history of cyclosporine therapy, and patients with underlying chronic renal insufficiency.^2,6,7 The most commonly affected tissues are those with poor blood supply and lower temperatures, such as the ear helix and first metacarpal joint.⁴ The auricle is the most common site of tophi on the head and neck. Tophi of the helices are generally asymptomatic and nontender; however, tophi can become large, inflamed, and ulcerated, causing pressure and discomfort.² Combination treatment with dietary modification and antihyperuricemic therapy (eg, allopurinol) has been shown to reduce the size of lesions and prevent future tophi formation. However, these results may take months, warranting excision of large and symptomatic lesions.^4,8

Our case is unusual in that the onset of the auricular lesions predated the articular gout by 6 months. Gouty tophi as the initial presentation of hyperuricemia is rare; however, tophi formation without concomitant arthritis has been reported.^2,3,7,9 Wernick et al⁷ described 6 patients presenting with tophi before the onset of inflammatory arthritis that they attributed to changes in active inflammation by age (eg, elderly patients were more commonly immunosuppressed), chronic illnesses, and anti-inflammatory medications (eg, nonsteroidal anti-inflammatory drugs). Another possible explanation for this atypical presentation is misdiagnosis caused by other forms of arthritis (eg, rheumatoid arthritis, osteoarthritis) masking acute gout episodes. It also has been reported that monosodium urate crystals can be found in synovial fluid with no inflammation and therefore no symptoms.⁷

Tophi, although rare, may be the sole clinical manifestation of underlying gouty disease. It is important to be aware of this atypical presentation to prevent misdiagnosis and provide appropriate treatment.

The Diagnosis: Bilateral Auricular Tophaceous Gout

Histopathologic evaluation with hematoxylin and eosin staining demonstrated clusters of abundant granular amorphous material within the subcutaneous tissue (Figure 1). The overlying epidermis and dermis were unremarkable. The granular amorphous material demonstrated numerous monosodium urate crystals under polarized light (Figure 2). At a return visit following the biopsy results, the patient reported a history of a single episode of monoarticular gouty arthritis involving the right hallux approximately 6 months after the onset of the skin lesions. With the added clinical history and the biopsy results, his serum uric acid level was obtained and was found to be elevated at 9.2 mg/dL (reference range, 3.5–8 mg/dL).

In our patient, the clinical differential diagnosis included calcium deposits, weathering nodules, and tophaceous gout. The differential diagnosis of auricular lesions is broad, and benign lesions may mimic cancerous entities such as basal cell carcinoma and squamous cell carcinoma.¹ Therefore a detailed history, thorough physical examination, and tissue sampling are key to establishing the correct diagnosis. Our patient’s history of monoarticular gouty arthritis was only elucidated after a diagnosis of bilateral auricular tophaceous gout was made based on the biopsy results.

Subcutaneous tophi represent a chronic state of hyperuricemia and tend to manifest after long-standing polyarthritis and repeated acute gout attacks.^2-5 These lesions develop in approximately 50% of gout patients and usually occur an average of 11.6 years after the onset of disease.² There is a subset of individuals that are at higher risk for developing tophi, including elderly and female patients, diuretic and chronic nonsteroidal anti-inflammatory drug users, patients with a history of cyclosporine therapy, and patients with underlying chronic renal insufficiency.^2,6,7 The most commonly affected tissues are those with poor blood supply and lower temperatures, such as the ear helix and first metacarpal joint.⁴ The auricle is the most common site of tophi on the head and neck. Tophi of the helices are generally asymptomatic and nontender; however, tophi can become large, inflamed, and ulcerated, causing pressure and discomfort.² Combination treatment with dietary modification and antihyperuricemic therapy (eg, allopurinol) has been shown to reduce the size of lesions and prevent future tophi formation. However, these results may take months, warranting excision of large and symptomatic lesions.^4,8

Our case is unusual in that the onset of the auricular lesions predated the articular gout by 6 months. Gouty tophi as the initial presentation of hyperuricemia is rare; however, tophi formation without concomitant arthritis has been reported.^2,3,7,9 Wernick et al⁷ described 6 patients presenting with tophi before the onset of inflammatory arthritis that they attributed to changes in active inflammation by age (eg, elderly patients were more commonly immunosuppressed), chronic illnesses, and anti-inflammatory medications (eg, nonsteroidal anti-inflammatory drugs). Another possible explanation for this atypical presentation is misdiagnosis caused by other forms of arthritis (eg, rheumatoid arthritis, osteoarthritis) masking acute gout episodes. It also has been reported that monosodium urate crystals can be found in synovial fluid with no inflammation and therefore no symptoms.⁷

Tophi, although rare, may be the sole clinical manifestation of underlying gouty disease. It is important to be aware of this atypical presentation to prevent misdiagnosis and provide appropriate treatment.

The Diagnosis: Bilateral Auricular Tophaceous Gout

Histopathologic evaluation with hematoxylin and eosin staining demonstrated clusters of abundant granular amorphous material within the subcutaneous tissue (Figure 1). The overlying epidermis and dermis were unremarkable. The granular amorphous material demonstrated numerous monosodium urate crystals under polarized light (Figure 2). At a return visit following the biopsy results, the patient reported a history of a single episode of monoarticular gouty arthritis involving the right hallux approximately 6 months after the onset of the skin lesions. With the added clinical history and the biopsy results, his serum uric acid level was obtained and was found to be elevated at 9.2 mg/dL (reference range, 3.5–8 mg/dL).

In our patient, the clinical differential diagnosis included calcium deposits, weathering nodules, and tophaceous gout. The differential diagnosis of auricular lesions is broad, and benign lesions may mimic cancerous entities such as basal cell carcinoma and squamous cell carcinoma.¹ Therefore a detailed history, thorough physical examination, and tissue sampling are key to establishing the correct diagnosis. Our patient’s history of monoarticular gouty arthritis was only elucidated after a diagnosis of bilateral auricular tophaceous gout was made based on the biopsy results.

Subcutaneous tophi represent a chronic state of hyperuricemia and tend to manifest after long-standing polyarthritis and repeated acute gout attacks.^2-5 These lesions develop in approximately 50% of gout patients and usually occur an average of 11.6 years after the onset of disease.² There is a subset of individuals that are at higher risk for developing tophi, including elderly and female patients, diuretic and chronic nonsteroidal anti-inflammatory drug users, patients with a history of cyclosporine therapy, and patients with underlying chronic renal insufficiency.^2,6,7 The most commonly affected tissues are those with poor blood supply and lower temperatures, such as the ear helix and first metacarpal joint.⁴ The auricle is the most common site of tophi on the head and neck. Tophi of the helices are generally asymptomatic and nontender; however, tophi can become large, inflamed, and ulcerated, causing pressure and discomfort.² Combination treatment with dietary modification and antihyperuricemic therapy (eg, allopurinol) has been shown to reduce the size of lesions and prevent future tophi formation. However, these results may take months, warranting excision of large and symptomatic lesions.^4,8

Our case is unusual in that the onset of the auricular lesions predated the articular gout by 6 months. Gouty tophi as the initial presentation of hyperuricemia is rare; however, tophi formation without concomitant arthritis has been reported.^2,3,7,9 Wernick et al⁷ described 6 patients presenting with tophi before the onset of inflammatory arthritis that they attributed to changes in active inflammation by age (eg, elderly patients were more commonly immunosuppressed), chronic illnesses, and anti-inflammatory medications (eg, nonsteroidal anti-inflammatory drugs). Another possible explanation for this atypical presentation is misdiagnosis caused by other forms of arthritis (eg, rheumatoid arthritis, osteoarthritis) masking acute gout episodes. It also has been reported that monosodium urate crystals can be found in synovial fluid with no inflammation and therefore no symptoms.⁷

Tophi, although rare, may be the sole clinical manifestation of underlying gouty disease. It is important to be aware of this atypical presentation to prevent misdiagnosis and provide appropriate treatment.

The Diagnosis: Acquired Acrodermatitis Enteropathica

Acquired acrodermatitis enteropathica (AAE) is a rare disorder caused by severe zinc deficiency. Although acrodermatitis enteropathica is an autosomal-recessive disorder that typically manifests in infancy, AAE also can result from poor zinc intake, impaired absorption, or accelerated losses. There are reports of AAE in patients with zinc-deficient diets,¹ eating disorders,² bariatric and other gastrointestinal surgeries,³ malabsorptive diseases,⁴ and nephrotic syndrome.⁵

Zinc plays an important role in DNA and RNA synthesis, reactive oxygen species attenuation, and energy metabolism, allowing for proper wound healing, skin differentiation, and proliferation.⁶ Zinc is found in most foods, but animal protein contains higher concentrations (Table).⁷ Approximately 85% of zinc is stored in muscles and bones, with only a small amount of accessible zinc available in the liver. Liver stores can be depleted as quickly as 1 week.⁸ Total parenteral nutrition without trace element supplementation can quickly predispose patients to AAE.

Diagnosis of this condition requires triangulation of clinical presentation, histopathology examination, and laboratory findings. Acrodermatitis enteropathica typically is characterized by dermatitis, diarrhea, and epidermal appendage findings. In its early stages, the dermatitis often manifests with angular cheilitis and paronychia.⁹ Patients then develop erythema, erosions, and occasionally vesicles or psoriasiform plaques in periorificial, perineal, and acral sites (Figure 1). Epidermal appendage effects include generalized alopecia and thinning nails with white transverse ridges. Although dermatologic and gastrointestinal manifestations are the most obvious, severe AAE may cause other symptoms, including mental slowing, hypogonadism, and impaired immune function.⁹

Histopathology of AAE skin lesions is similar to other nutritional deficiencies. Early changes are more specific to deficiency dermatitis and include cytoplasmic pallor and ballooning degeneration of keratinocytes in the stratum spinosum and granulosum.⁹ Necrolysis results in confluent keratinocyte necrosis developing into subcorneal bulla. Later in the disease course, the presentation becomes psoriasiform with keratinocyte dyskeratosis and confluent parakeratosis¹⁰ (Figure 2). Dermal edema with dilated tortuous vessels and a neutrophilic infiltrate may be present throughout disease progression.

Common laboratory abnormalities used to confirm zinc deficiency are decreased plasma zinc and alkaline phosphatase levels. Plasma zinc levels should be drawn after fasting because zinc levels decrease after food intake.⁹ Concurrent albumin levels should be drawn to correct for low levels caused by hypoalbuminemia. Acquired acrodermatitis enteropathica has been seen in patients with only mildly decreased plasma zinc levels or even zinc levels within reference range.¹¹ Alkaline phosphatase metalloenzyme synthesis requires zinc and a decreased level suggests zinc deficiency even with a plasma zinc level within reference range. Alkaline phosphatase levels usually can be ascertained in a matter of hours, while the zinc levels take much longer to result.

Acquired acrodermatitis enteropathica is treated with oral elemental zinc supplementation at 1 to 2 mg/kg daily.¹² Diarrhea typically resolves within 24 hours, but skin lesions heal in 1 to 2 weeks or longer. Although there is no consensus on when to discontinue zinc replacement therapy, therapy generally is not lifelong. Once the patient is zinc replete and the inciting factor has resolved, patients can discontinue supplementation without risk for recurrence.

Trace elements had not been added to our patient’s total parenteral nutrition prior to admission. Basic nutrition laboratory results and zinc levels returned markedly low: 14 μg/dL (reference range, 60–120 μg/dL). Alkaline phosphatase, a zinc-dependent protein, also was low at 12 U/L (reference range, 40–150 U/L). We added trace elements and vitamins and began empiric zinc replacement with 440 mg oral zinc sulfate daily (100 mg elemental zinc). Cephalexin was prescribed for impetiginized skin lesions. The patient noted skin improvement after 3 days on zinc replacement therapy.

The Diagnosis: Acquired Acrodermatitis Enteropathica

Acquired acrodermatitis enteropathica (AAE) is a rare disorder caused by severe zinc deficiency. Although acrodermatitis enteropathica is an autosomal-recessive disorder that typically manifests in infancy, AAE also can result from poor zinc intake, impaired absorption, or accelerated losses. There are reports of AAE in patients with zinc-deficient diets,¹ eating disorders,² bariatric and other gastrointestinal surgeries,³ malabsorptive diseases,⁴ and nephrotic syndrome.⁵

Zinc plays an important role in DNA and RNA synthesis, reactive oxygen species attenuation, and energy metabolism, allowing for proper wound healing, skin differentiation, and proliferation.⁶ Zinc is found in most foods, but animal protein contains higher concentrations (Table).⁷ Approximately 85% of zinc is stored in muscles and bones, with only a small amount of accessible zinc available in the liver. Liver stores can be depleted as quickly as 1 week.⁸ Total parenteral nutrition without trace element supplementation can quickly predispose patients to AAE.

Diagnosis of this condition requires triangulation of clinical presentation, histopathology examination, and laboratory findings. Acrodermatitis enteropathica typically is characterized by dermatitis, diarrhea, and epidermal appendage findings. In its early stages, the dermatitis often manifests with angular cheilitis and paronychia.⁹ Patients then develop erythema, erosions, and occasionally vesicles or psoriasiform plaques in periorificial, perineal, and acral sites (Figure 1). Epidermal appendage effects include generalized alopecia and thinning nails with white transverse ridges. Although dermatologic and gastrointestinal manifestations are the most obvious, severe AAE may cause other symptoms, including mental slowing, hypogonadism, and impaired immune function.⁹

Histopathology of AAE skin lesions is similar to other nutritional deficiencies. Early changes are more specific to deficiency dermatitis and include cytoplasmic pallor and ballooning degeneration of keratinocytes in the stratum spinosum and granulosum.⁹ Necrolysis results in confluent keratinocyte necrosis developing into subcorneal bulla. Later in the disease course, the presentation becomes psoriasiform with keratinocyte dyskeratosis and confluent parakeratosis¹⁰ (Figure 2). Dermal edema with dilated tortuous vessels and a neutrophilic infiltrate may be present throughout disease progression.

Common laboratory abnormalities used to confirm zinc deficiency are decreased plasma zinc and alkaline phosphatase levels. Plasma zinc levels should be drawn after fasting because zinc levels decrease after food intake.⁹ Concurrent albumin levels should be drawn to correct for low levels caused by hypoalbuminemia. Acquired acrodermatitis enteropathica has been seen in patients with only mildly decreased plasma zinc levels or even zinc levels within reference range.¹¹ Alkaline phosphatase metalloenzyme synthesis requires zinc and a decreased level suggests zinc deficiency even with a plasma zinc level within reference range. Alkaline phosphatase levels usually can be ascertained in a matter of hours, while the zinc levels take much longer to result.

Acquired acrodermatitis enteropathica is treated with oral elemental zinc supplementation at 1 to 2 mg/kg daily.¹² Diarrhea typically resolves within 24 hours, but skin lesions heal in 1 to 2 weeks or longer. Although there is no consensus on when to discontinue zinc replacement therapy, therapy generally is not lifelong. Once the patient is zinc replete and the inciting factor has resolved, patients can discontinue supplementation without risk for recurrence.

Trace elements had not been added to our patient’s total parenteral nutrition prior to admission. Basic nutrition laboratory results and zinc levels returned markedly low: 14 μg/dL (reference range, 60–120 μg/dL). Alkaline phosphatase, a zinc-dependent protein, also was low at 12 U/L (reference range, 40–150 U/L). We added trace elements and vitamins and began empiric zinc replacement with 440 mg oral zinc sulfate daily (100 mg elemental zinc). Cephalexin was prescribed for impetiginized skin lesions. The patient noted skin improvement after 3 days on zinc replacement therapy.

The Diagnosis: Acquired Acrodermatitis Enteropathica

Acquired acrodermatitis enteropathica (AAE) is a rare disorder caused by severe zinc deficiency. Although acrodermatitis enteropathica is an autosomal-recessive disorder that typically manifests in infancy, AAE also can result from poor zinc intake, impaired absorption, or accelerated losses. There are reports of AAE in patients with zinc-deficient diets,¹ eating disorders,² bariatric and other gastrointestinal surgeries,³ malabsorptive diseases,⁴ and nephrotic syndrome.⁵

Zinc plays an important role in DNA and RNA synthesis, reactive oxygen species attenuation, and energy metabolism, allowing for proper wound healing, skin differentiation, and proliferation.⁶ Zinc is found in most foods, but animal protein contains higher concentrations (Table).⁷ Approximately 85% of zinc is stored in muscles and bones, with only a small amount of accessible zinc available in the liver. Liver stores can be depleted as quickly as 1 week.⁸ Total parenteral nutrition without trace element supplementation can quickly predispose patients to AAE.

Diagnosis of this condition requires triangulation of clinical presentation, histopathology examination, and laboratory findings. Acrodermatitis enteropathica typically is characterized by dermatitis, diarrhea, and epidermal appendage findings. In its early stages, the dermatitis often manifests with angular cheilitis and paronychia.⁹ Patients then develop erythema, erosions, and occasionally vesicles or psoriasiform plaques in periorificial, perineal, and acral sites (Figure 1). Epidermal appendage effects include generalized alopecia and thinning nails with white transverse ridges. Although dermatologic and gastrointestinal manifestations are the most obvious, severe AAE may cause other symptoms, including mental slowing, hypogonadism, and impaired immune function.⁹

Histopathology of AAE skin lesions is similar to other nutritional deficiencies. Early changes are more specific to deficiency dermatitis and include cytoplasmic pallor and ballooning degeneration of keratinocytes in the stratum spinosum and granulosum.⁹ Necrolysis results in confluent keratinocyte necrosis developing into subcorneal bulla. Later in the disease course, the presentation becomes psoriasiform with keratinocyte dyskeratosis and confluent parakeratosis¹⁰ (Figure 2). Dermal edema with dilated tortuous vessels and a neutrophilic infiltrate may be present throughout disease progression.

Common laboratory abnormalities used to confirm zinc deficiency are decreased plasma zinc and alkaline phosphatase levels. Plasma zinc levels should be drawn after fasting because zinc levels decrease after food intake.⁹ Concurrent albumin levels should be drawn to correct for low levels caused by hypoalbuminemia. Acquired acrodermatitis enteropathica has been seen in patients with only mildly decreased plasma zinc levels or even zinc levels within reference range.¹¹ Alkaline phosphatase metalloenzyme synthesis requires zinc and a decreased level suggests zinc deficiency even with a plasma zinc level within reference range. Alkaline phosphatase levels usually can be ascertained in a matter of hours, while the zinc levels take much longer to result.

Acquired acrodermatitis enteropathica is treated with oral elemental zinc supplementation at 1 to 2 mg/kg daily.¹² Diarrhea typically resolves within 24 hours, but skin lesions heal in 1 to 2 weeks or longer. Although there is no consensus on when to discontinue zinc replacement therapy, therapy generally is not lifelong. Once the patient is zinc replete and the inciting factor has resolved, patients can discontinue supplementation without risk for recurrence.

Trace elements had not been added to our patient’s total parenteral nutrition prior to admission. Basic nutrition laboratory results and zinc levels returned markedly low: 14 μg/dL (reference range, 60–120 μg/dL). Alkaline phosphatase, a zinc-dependent protein, also was low at 12 U/L (reference range, 40–150 U/L). We added trace elements and vitamins and began empiric zinc replacement with 440 mg oral zinc sulfate daily (100 mg elemental zinc). Cephalexin was prescribed for impetiginized skin lesions. The patient noted skin improvement after 3 days on zinc replacement therapy.

Lichen striatus (LS) is a benign, uncommon, self-limited, linear inflammatory skin disorder that primarily affects children up to 15 years of age, most commonly around 2 to 3 years of age, and is seen more frequently in girls.¹ It presents with a sudden eruption of asymptomatic small, flat-topped, lichenoid, scaly papules in a linear array on a single extremity. The lesions may be erythematous, flesh colored, or hypopigmented.^1,2 Multiple lesions appear over days to weeks and coalesce into linear plaques in a continuous or interrupted pattern along the lines of Blaschko, indicating possible somatic mosaicism.¹ Although typically asymptomatic, it may be pruritic. Most cases spontaneously resolve within 1 year.³ Recurrences are unusual. Digital involvement may result in onycholysis, longitudinal ridging, splitting, and nail loss.¹ The underlying cause of LS may be an abnormal immunologic reaction or genetic predisposition that is precipitated by some trigger such as a viral infection, trauma, hypersensitivity reaction, vaccine, seasonal variation, medication, or pregnancy.^1,2 An association with atopy has been described. Treatment is not necessary but options include topical steroids, topical retinoids, and topical calcineurin inhibitors.²

Histologically, findings in LS are somewhat variable but typically show a combination of spongiotic and lichenoid interface dermatitis with a perivascular and periadnexal lymphocytic infiltrate (Figure 1). Epidermal changes include intercellular and intracellular edema, focal spongiosis, lymphocytic exocytosis, parakeratosis, patchy hyperkeratosis, and keratinocyte necrosis (Figure 2A).^1,3 The epidermis is normal or slightly acanthotic, and dyskeratotic keratinocytes can be found in the granular and horny layers or at the dermoepidermal junction.² The lymphohistiocytic infiltrate in the superficial and deep dermis surrounds vascular plexuses and cutaneous adnexa such as eccrine glands and hair follicles.¹ Perivascular lymphoid aggregates and eccrine coil involvement are particularly distinctive of LS (Figure 2B).⁴ Pigment incontinence also may be seen.

Another condition that distributes linearly along the lines of Blaschko is linear epidermolytic hyperkeratosis (EHK). Similar to LS, histology shows hyperkeratosis, focal parakeratosis, and acanthosis of the epidermis.⁵ However, EHK shows epidermolysis, acantholysis, and perinuclear vacuolization in spinous and granular layers (Figure 3).⁵ The lack of perivascular and periadnexal inflammation also can help differentiate EHK from LS.

Linear lichen planus (LLP), similar to LS, histologically shows a lichenoid lymphocytic bandlike infiltrate obscuring the dermoepidermal junction, vacuolization of the basal cell layer, and pigment incontinence.^1,2 Although LS and LLP can have histologic overlap, the absence of adnexal or perieccrine lymphocytic inflammation can help distinguish the two.³ The histopathologic changes of intercellular edema or mild spongiosis, exocytosis, and parakeratosis present in LS also are typically absent in LLP. Linear lichen planus characteristically consists of wedge-shaped hypergranulosis and irregular acanthosis with saw-toothed rete ridges (Figure 4).² In addition, lobular eosinophilic deposits known as cytoid or Civatte bodies representing degenerated keratinocytes can be visualized at the dermoepidermal junction in LLP.² Immunofluorescence will highlight Civatte bodies with IgM, IgG, and C3, also helping to differentiate these 2 conditions.¹

Linear porokeratosis can be mistaken for the linear lesion of LS. Both entities may reveal perivascular lymphocytes in the dermis, and porokeratosis can be lichenoid in the central portion of the lesion.⁶ However, porokeratosis is unique in that it contains a cornoid lamella, characterized by a thin column of tightly packed parakeratotic cells extending from an invagination of the epidermis through the adjacent stratum corneum (Figure 5).⁶ Beneath the cornoid lamella, the granular layer is either absent or markedly attenuated, and pyknotic keratinocytes with perinuclear edema are present in the spinous layer.⁶ The epidermis in the central portion of the porokeratotic lesion may be normal, hyperplastic, or atrophic with effacement of rete ridges.

Similar to LS, linear psoriasis follows lines of Blaschko clinically. However, it is distinguished by its characteristic psoriatic epidermal changes as well as its lack of lichenoid or perieccrine inflammation.³ Typical findings in linear psoriasis include hyperkeratosis, confluent parakeratosis with entrapped neutrophilic microabscesses, acanthosis with regular elongation of rete ridges, intraepidermal neutrophils, thinned suprapapillary plates, dilated capillaries in the tips of the dermal papillae, and a chronic dermal inflammatory infiltrate (Figure 6).⁴

Lichen striatus (LS) is a benign, uncommon, self-limited, linear inflammatory skin disorder that primarily affects children up to 15 years of age, most commonly around 2 to 3 years of age, and is seen more frequently in girls.¹ It presents with a sudden eruption of asymptomatic small, flat-topped, lichenoid, scaly papules in a linear array on a single extremity. The lesions may be erythematous, flesh colored, or hypopigmented.^1,2 Multiple lesions appear over days to weeks and coalesce into linear plaques in a continuous or interrupted pattern along the lines of Blaschko, indicating possible somatic mosaicism.¹ Although typically asymptomatic, it may be pruritic. Most cases spontaneously resolve within 1 year.³ Recurrences are unusual. Digital involvement may result in onycholysis, longitudinal ridging, splitting, and nail loss.¹ The underlying cause of LS may be an abnormal immunologic reaction or genetic predisposition that is precipitated by some trigger such as a viral infection, trauma, hypersensitivity reaction, vaccine, seasonal variation, medication, or pregnancy.^1,2 An association with atopy has been described. Treatment is not necessary but options include topical steroids, topical retinoids, and topical calcineurin inhibitors.²

Histologically, findings in LS are somewhat variable but typically show a combination of spongiotic and lichenoid interface dermatitis with a perivascular and periadnexal lymphocytic infiltrate (Figure 1). Epidermal changes include intercellular and intracellular edema, focal spongiosis, lymphocytic exocytosis, parakeratosis, patchy hyperkeratosis, and keratinocyte necrosis (Figure 2A).^1,3 The epidermis is normal or slightly acanthotic, and dyskeratotic keratinocytes can be found in the granular and horny layers or at the dermoepidermal junction.² The lymphohistiocytic infiltrate in the superficial and deep dermis surrounds vascular plexuses and cutaneous adnexa such as eccrine glands and hair follicles.¹ Perivascular lymphoid aggregates and eccrine coil involvement are particularly distinctive of LS (Figure 2B).⁴ Pigment incontinence also may be seen.

Another condition that distributes linearly along the lines of Blaschko is linear epidermolytic hyperkeratosis (EHK). Similar to LS, histology shows hyperkeratosis, focal parakeratosis, and acanthosis of the epidermis.⁵ However, EHK shows epidermolysis, acantholysis, and perinuclear vacuolization in spinous and granular layers (Figure 3).⁵ The lack of perivascular and periadnexal inflammation also can help differentiate EHK from LS.

Linear lichen planus (LLP), similar to LS, histologically shows a lichenoid lymphocytic bandlike infiltrate obscuring the dermoepidermal junction, vacuolization of the basal cell layer, and pigment incontinence.^1,2 Although LS and LLP can have histologic overlap, the absence of adnexal or perieccrine lymphocytic inflammation can help distinguish the two.³ The histopathologic changes of intercellular edema or mild spongiosis, exocytosis, and parakeratosis present in LS also are typically absent in LLP. Linear lichen planus characteristically consists of wedge-shaped hypergranulosis and irregular acanthosis with saw-toothed rete ridges (Figure 4).² In addition, lobular eosinophilic deposits known as cytoid or Civatte bodies representing degenerated keratinocytes can be visualized at the dermoepidermal junction in LLP.² Immunofluorescence will highlight Civatte bodies with IgM, IgG, and C3, also helping to differentiate these 2 conditions.¹

Linear porokeratosis can be mistaken for the linear lesion of LS. Both entities may reveal perivascular lymphocytes in the dermis, and porokeratosis can be lichenoid in the central portion of the lesion.⁶ However, porokeratosis is unique in that it contains a cornoid lamella, characterized by a thin column of tightly packed parakeratotic cells extending from an invagination of the epidermis through the adjacent stratum corneum (Figure 5).⁶ Beneath the cornoid lamella, the granular layer is either absent or markedly attenuated, and pyknotic keratinocytes with perinuclear edema are present in the spinous layer.⁶ The epidermis in the central portion of the porokeratotic lesion may be normal, hyperplastic, or atrophic with effacement of rete ridges.

Similar to LS, linear psoriasis follows lines of Blaschko clinically. However, it is distinguished by its characteristic psoriatic epidermal changes as well as its lack of lichenoid or perieccrine inflammation.³ Typical findings in linear psoriasis include hyperkeratosis, confluent parakeratosis with entrapped neutrophilic microabscesses, acanthosis with regular elongation of rete ridges, intraepidermal neutrophils, thinned suprapapillary plates, dilated capillaries in the tips of the dermal papillae, and a chronic dermal inflammatory infiltrate (Figure 6).⁴

Lichen striatus (LS) is a benign, uncommon, self-limited, linear inflammatory skin disorder that primarily affects children up to 15 years of age, most commonly around 2 to 3 years of age, and is seen more frequently in girls.¹ It presents with a sudden eruption of asymptomatic small, flat-topped, lichenoid, scaly papules in a linear array on a single extremity. The lesions may be erythematous, flesh colored, or hypopigmented.^1,2 Multiple lesions appear over days to weeks and coalesce into linear plaques in a continuous or interrupted pattern along the lines of Blaschko, indicating possible somatic mosaicism.¹ Although typically asymptomatic, it may be pruritic. Most cases spontaneously resolve within 1 year.³ Recurrences are unusual. Digital involvement may result in onycholysis, longitudinal ridging, splitting, and nail loss.¹ The underlying cause of LS may be an abnormal immunologic reaction or genetic predisposition that is precipitated by some trigger such as a viral infection, trauma, hypersensitivity reaction, vaccine, seasonal variation, medication, or pregnancy.^1,2 An association with atopy has been described. Treatment is not necessary but options include topical steroids, topical retinoids, and topical calcineurin inhibitors.²

Histologically, findings in LS are somewhat variable but typically show a combination of spongiotic and lichenoid interface dermatitis with a perivascular and periadnexal lymphocytic infiltrate (Figure 1). Epidermal changes include intercellular and intracellular edema, focal spongiosis, lymphocytic exocytosis, parakeratosis, patchy hyperkeratosis, and keratinocyte necrosis (Figure 2A).^1,3 The epidermis is normal or slightly acanthotic, and dyskeratotic keratinocytes can be found in the granular and horny layers or at the dermoepidermal junction.² The lymphohistiocytic infiltrate in the superficial and deep dermis surrounds vascular plexuses and cutaneous adnexa such as eccrine glands and hair follicles.¹ Perivascular lymphoid aggregates and eccrine coil involvement are particularly distinctive of LS (Figure 2B).⁴ Pigment incontinence also may be seen.

Another condition that distributes linearly along the lines of Blaschko is linear epidermolytic hyperkeratosis (EHK). Similar to LS, histology shows hyperkeratosis, focal parakeratosis, and acanthosis of the epidermis.⁵ However, EHK shows epidermolysis, acantholysis, and perinuclear vacuolization in spinous and granular layers (Figure 3).⁵ The lack of perivascular and periadnexal inflammation also can help differentiate EHK from LS.

Linear lichen planus (LLP), similar to LS, histologically shows a lichenoid lymphocytic bandlike infiltrate obscuring the dermoepidermal junction, vacuolization of the basal cell layer, and pigment incontinence.^1,2 Although LS and LLP can have histologic overlap, the absence of adnexal or perieccrine lymphocytic inflammation can help distinguish the two.³ The histopathologic changes of intercellular edema or mild spongiosis, exocytosis, and parakeratosis present in LS also are typically absent in LLP. Linear lichen planus characteristically consists of wedge-shaped hypergranulosis and irregular acanthosis with saw-toothed rete ridges (Figure 4).² In addition, lobular eosinophilic deposits known as cytoid or Civatte bodies representing degenerated keratinocytes can be visualized at the dermoepidermal junction in LLP.² Immunofluorescence will highlight Civatte bodies with IgM, IgG, and C3, also helping to differentiate these 2 conditions.¹

Linear porokeratosis can be mistaken for the linear lesion of LS. Both entities may reveal perivascular lymphocytes in the dermis, and porokeratosis can be lichenoid in the central portion of the lesion.⁶ However, porokeratosis is unique in that it contains a cornoid lamella, characterized by a thin column of tightly packed parakeratotic cells extending from an invagination of the epidermis through the adjacent stratum corneum (Figure 5).⁶ Beneath the cornoid lamella, the granular layer is either absent or markedly attenuated, and pyknotic keratinocytes with perinuclear edema are present in the spinous layer.⁶ The epidermis in the central portion of the porokeratotic lesion may be normal, hyperplastic, or atrophic with effacement of rete ridges.

Similar to LS, linear psoriasis follows lines of Blaschko clinically. However, it is distinguished by its characteristic psoriatic epidermal changes as well as its lack of lichenoid or perieccrine inflammation.³ Typical findings in linear psoriasis include hyperkeratosis, confluent parakeratosis with entrapped neutrophilic microabscesses, acanthosis with regular elongation of rete ridges, intraepidermal neutrophils, thinned suprapapillary plates, dilated capillaries in the tips of the dermal papillae, and a chronic dermal inflammatory infiltrate (Figure 6).⁴