Verrucous psoriasis: A rare variant of psoriasis masqueradin
Verrucous psoriasis (VP) is a rare variant of psoriasis characterized by hyperkeratotic, papillomatous plaques that clinically resemble verrucous carcinoma (VC) in lesion appearance and distribution. It is amenable to medical treatments. Conversely, VC, a rare subtype of well-differentiated squamous cell carcinoma, is treated with surgical excision. Histologically, they may be difficult to differentiate.

An 81-year-old white man with a history of mild plaque psoriasis, nonmelanoma skin cancer, and alcohol use presented for evaluation of a lesion on the foot that had been enlarging over several months. It was causing tenderness and difficulty walking. He had no recent travel history. Relevant dermatologic medications included clobetasol cream for psoriasis, but he had not been using it because his skin disease had been quiescent.

Physical examination was unremarkable except for a 2×2.5 cm, verrucous, well-circumscribed, tan-tobrown plaque on the medial left heel with surrounding erythema. The differential diagnosis favored squamous cell carcinoma versus a deep fungal infection. Two punch biopsies were performed. Histopathology showed an atypical squamous proliferation; the tissue culture result was negative for a fungal infection. Two months later, the patient returned because the lesion had grown to 4 cm.

Source: JAAD case reports

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