Case Number : Case 2621 - 23 July 2020 Posted By: Saleem Taibjee

To me this looks like well-differentiated invasive squamous cell carcinoma.  I am not convinced that it has originated locally as connection with the epidermis is tenuous and the overlying epidermis shows neither much in the way of dysplasia nor any sign of ulceration. Perhaps this is intravascular spread from a nearby primary SCC.

I think tumor shows squamoid and ductal differantiation.

My thought is squamoid eccrine ductal carcinoma.

Squamoid eccrine ductal carcinoma

Squamoid eccrine ductal carcinoma

immunostain below

I was thinking of a solid variant of MAC, but this looks like a high grade carcinoma. So favor a Porocarcinoma. 

Yes, I favoured squamoid eccrine ductal carcinoma. Low power shows a poorly demarcated and infiltrative tumour extending into subcutis. The superficial aspect shows focal connection with the epidermis and infundibula, with prominent squamoid differentiation. At the deep aspect the tumour is more infiltrative with ductal differentiation evident; cuticle-like lumina and intracytoplasmic vacuoles, also highlighted by the CEA. There is variable cytological atypia and mitotic activity.