Facial HPV6-Positive in Situ Squamous Cell Carcinoma With Small Cell Features Mimicking Merkel Cell Carcinoma.

We describe a previously unreported variant of cutaneous squamous cell carcinoma in situ (SCCis) with small cell morphology mimicking intraepidermal Merkel cell carcinoma. The lesion, arising on the upper lip of an 86-year-old man, displayed biphasic histology: a predominant population of small basaloid cells and a superficial bowenoid component. Immunohistochemistry showed divergent expression patterns, and PCR confirmed HPV6. Complete spontaneous regression occurred post-biopsy. This case expands the histopathologic spectrum of SCCis and suggests an intraepidermal basaloid variant potentially linked to low-risk alpha HPV.