Skin nonmelanocytic tumor

• Skin disorder of abnormal clonal keratinization with various clinical expressions and subtypes
• Characterized by 1 or more variably sized lesions on the skin that are rimmed by a hyperkeratotic border

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• Cornoid lamella (Actas Dermosifiliogr (Engl Ed) 2020;111:545, Indian J Dermatol Venereol Leprol 2022;88:291)
  • Column of parakeratosis at 45 degree angle
  • Underlying dyskeratosis with focal loss of granular layer
• Dilated capillaries in the papillary dermis are associated with a lymphocytic infiltrate (Patterson: Weedon's Skin Pathology, 5th Edition, 2020)
  • Most prominent inflammatory changes are seen in DSAP
• Central to coronoid lamella, epidermis may be atrophic, normal thickness or acanthotic
  • Central interface dermatitis or psoriasiform dermatitis possible
• Solar elastosis possible in DSAP
• Multiple cornoid lamellae can be seen in porokeratosis ptychotropica or penoscrotal porokeratosis

Contributed by Wei-Shen Chen, M.D., Ph.D.

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• Skin, right upper arm, skin shave:
  • Porokeratosis (see comment)
  • Comment: Sections show tiers of parakeratosis overlying dyskeratotic keratinocytes. If multiple lesions are present clinically, a diagnosis of DSAP should be considered.

• Skin, right scrotum, skin shave:
  • Porokeratosis (see comment)
  • Comment: Sections show acanthosis with multifocal columns of parakeratosis overlying dyskeratotic keratinocytes. At this anatomic site, the findings are consistent with a diagnosis of penoscrotal porokeratosis.

• Porokeratoma:
  • Benign acanthoma (Am J Surg Pathol 2007;31:1897)
  • Characterized by multiple cornoid lamellae embedded within a single verrucous lesion (Am J Dermatopathol 2022;44:748)
• Verrucae:
  • Epidermal acanthosis, papillomatosis with tiers of parakeratosis and koilocytosis
• Actinic keratosis:
  • Gritty papules in sun exposed sites
  • Histology with lower keratinocyte atypia and disorder
  • Cornoid lamella uncommonly seen
• Psoriasis:
  • Regular acanthosis with parakeratosis and intracorneal neutrophils (Munro microabscesses)
• Porokeratotic eccrine ostial and dermal duct nervus:
  • An eccrine hamartoma with punctate hyperkeratotic papules affecting the palms and soles
  • Histologically and clinically could appear like punctate porokeratosis but cornoid lamellae are limited to eccrine ostia
• Tinea corporis (Am J Clin Dermatol 2022;23:37):
  • Foci of parakeratosis with intracorneal hyphae

A 40 year old woman presented with an erythematous, annular macule with a thread-like, raised border on her arm. She had several similar lesions on her extensor arms. What is the most likely diagnosis?

1. Disseminated superficial actinic porokeratosis
2. Guttate psoriasis
3. Macular seborrheic keratoses
4. Nummular eczema
5. Tinea corporis

A. Disseminated superficial actinic porokeratosis. This patient has disseminated superficial actinic porokeratosis, which classically presents as small, annular macules with thread-like raised borders. It usually presents more diffusely than other porokeratosis subtypes and frequently on sun exposed areas (posterior neck, extensor surfaces of arms, legs). The histological finding of cornoid lamella is characteristic of porokeratosis.

Answer B is incorrect because guttate psoriasis is a variant of psoriasis that presents in children and adolescents following streptococcal infection (StatPearls: Guttate Psoriasis [Accessed 7 August 2023]). Although guttate psoriasis may also present as lesions over the extensor surfaces, biopsy would reveal a psoriasiform reaction pattern. There is less acanthosis than seen in psoriasis vulgaris. Other features of psoriasis include dilated superficial blood vessels, parakeratosis and neutrophils in the stratum corneum (microabscesses of Munro) (StatPearls: Guttate Psoriasis [Accessed 7 August 2023]).

Answer C is incorrect because seborrheic keratoses are benign lesions that classically present as waxy papules or plaques with a stuck on appearance. Histologic features include hyperkeratosis, acanthosis and papillomatosis (Dermatol Online J 2019;25:13030).

Answer D is incorrect because nummular eczema is a chronic skin condition characterized by oval or coin shaped, erythematous, eczematous plaques. These lesions are usually symmetrically distributed with a predilection for the lower and upper extremities (Recent Pat Inflamm Allergy Drug Discov 2020;14:146). Predominant features of eczema are spongiosis, acanthosis and exocytosis of inflammatory cells.

Answer E is incorrect because tinea corporis is a superficial dermatophyte infection that may clinically resemble porokeratosis due to its annular appearance. Histopathology shows hyphal forms in the stratum corneum.

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Reference: Porokeratosis

A 28 year old man presented with a 7 month history of a persistent rash over the scrotum and shaft of the penis associated with erythema, burning and pruritis. Clinical examination revealed a well circumscribed, erythematous plaque with a raised border and atrophic center. Poorly defined patches were also seen on the penile shaft. A punch biopsy revealed multiple cornoid lamellae. What is the most likely diagnosis?

1. Bowen disease
2. Condyloma acuminatum
3. Penoscrotal porokeratosis
4. Verruciform xanthoma
5. Zoon balanitis

C. Penoscrotal porokeratosis. This patient's clinical pathologic presentation is consistent with a diagnosis of penoscrotal porokeratosis, a distinct variant of porokeratosis that is often self resolving. This variant is seen in young males typically during the third decade of life (Indian Dermatol Online J 2015;6:339). Histology demonstrates multiple cornoid lamellae involving a mildly hyperplastic epidermis.

Answer A is incorrect because Bowen disease is a form of in situ squamous cell carcinoma. Although Bowen disease may present similarly to porokeratosis, it is rare in patients younger than 30 years of age (Indian Dermatol Online J 2022;13:177). Histopathology would demonstrate full thickness keratinocyte atypia (Indian Dermatol Online J 2022;13:177).

Answer B is incorrect because condyloma acuminata are anogenital warts caused by the human papillomavirus (HPV), most commonly HPV strains 6 and 11 (StatPearls: Condyloma Acuminata [Accessed 19 January 2024]). Similar to porokeratosis, condyloma acuminata display hyperkeratosis on histopathological evaluation. However, distinctive koilocytes are also expected. Additionally, condyloma acuminata lesions are usually found in groups that may coalesce into larger lesions and most often present as fleshy papules that range in size.

Answer D is incorrect because verruciform xanthoma is a rare mucocutaneous verrucopapillary lesion that is not associated with dyslipidemia. Histopathology demonstrates epithelial hyperplasia with prominent parakeratinization. The histological hallmark is the presence of foam cells or xanthoma cells confined to the connective tissue papillae (J Oral Maxillofac Pathol 2019;23:43).

Answer E is incorrect because Zoon balanitis is a nonvenereal condition that most commonly affects middle aged to older uncircumcised men. It most commonly presents as a single shiny erythematous plaque on the glans penis. Early cases will reveal thickening of the epidermis, parakeratosis and a patchy lichenoid infiltrate of lymphocytes and numerous plasma cells. Atrophy of the epidermis, superficial erosions, scattered neutrophils in the upper epidermis, scant spongiosis and a denser plasmacytic infiltrate may be seen in later stages (Indian J Sex Transm Dis AIDS 2016;37:129).

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Reference: Porokeratosis