Case Number : Case 1985 - 12 Jan 2018 Posted By: Dr. Richard Carr

Looks like porocarcinoma

Agreed. But the the stroma looks strange in the last figure. Maybe with mitoses. Need higher power to evaluate mitoses in the stroma. I'm thinking of a carcinosarcoma. 

First hypothesis is sebaceous carcinoma, sebaceoma like (rippled pattern, pagetoid infiltration of the epidermis, ulceration). Another a lot less likely hypothesis is BCC with sebaceous differentiation

Sebaceous carcinoma is a good thought.

Tough one. We may need some help with immuno-stains, perhaps? The cells seem small for a straightforward sebaceous carcinoma but with the intraepidermal involvement and facial location, it seems like a good thought. There are areas with 'bubbly' cytoplasm. I am favoring an adnexal neoplasm of some kind - eccrine carcinoma? I haven't been able to banish basal cell carcinoma of some kind, common things being common.

There is some IHC hopefully it will be posted soon.  Thanks for all the comments.

I favor sebaceous carcinoma, although the Ber-EP4 positivity. Nice sebaceoma like rippled  pattern. 

Thanks for all the suggestions. I agree the rippled pattern would be suggestive of sebaceoma but given the tumour arose in the proximity and in direct continuity with bowenoid epidermal dysplasia and that I could not see any clear cut sebaceous differentiation I opted for a undifferentiated (bowenoid) SCC. We've noted previously that basaloid bowens & SCC not infrequently show moderate strength BerEP4 expression but it lacks strong and accentuated peripheral palisading seen in BCC. We've also found that in contrast to sebaceoma, which are generally BerEP4 negative, sebaceous carcinomas show dual positive expression with BerEP4 and EMA in most cases. There is a small published study in peri-ocular sebaceous carcinoma that had a similar finding. Given that tumour had pushing only borders I commented that it might not be associated with a high risk for metastasis despite the thickness. One might even wonder if, for practical purposes, it was in situ still.

Interesting case

I forgot to say neuroendocrine markers were negative. We are finding a few "non-Merkel" carcinomas with neuroendocrine differentiation typically arising in association with Bowen's or basaloid SCC (sometimes follicular) that lack the polyoma virus and are typically CK20 negative. Keep an eye out for them as they need to be collected in to a substantial series. Unlike classical Merkel's they are usually quite cohesive / epithelial sheet-like in pattern.