Eccrine Carcinoma in Situ Arising in Eccrine Poroma

The background lesion is an eccrine poroma with a prominent intraepidermal component (hidroacanthoma simplex-like). Such lesions can exhibit variable atypia and as well carcinomas can arise in pre-existing eccrine poromas. In this particular case there is indeed supervening severe epithelial cell atypia whereby there are many positive staining cells for Ki67. The lesion is best treated and categorized as evolving eccrine carcinoma in situ arising in a background of eccrine poroma. As the lesion is in situ without invasion complete excision without sentinel lymph node sampling is reasonable.

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Slide 1: 79 year-old woman with a right foot bleeding papule. The excision specimen shows a fairly broad based intraepidermal squamous proliferative lesion.

Slide 2: The lesion assumes an interanastomosing growth pattern with a hypervascular stromal background.

Slide 3: There are clear cut duct structures within this lesion. The lesion does exhibit a clonal growth pattern with focal severe atypia albeit of a monotypic form.