Case Number : Case 2751 - 21 January 2021 Posted By: Saleem Taibjee

Porocarcinoma vs Sebaceous Carcinoma (I favor the first)

BCC. 

Cannot decide, but this malignant-looking tumour has epidermal connection with a nodular-cystic silhouette and cells with nuclear pleomorphism, frequent mitoses and small amount of cytoplasm (some vacuolated). Necrosis is also seen. Not very obvious ductal lumina seen intracytoplasmically, and pre-existing poroma or other tumours not too obvious? Thinking we need to exclude a strange-looking BCC or sebaceous carcinoma, or something distinctive which I am not familiar with... 

Not sure- may be metatypical BCC or basaloid SCC

This has poroid features but also peripheral pallisading and retraction artifact. Diff: BCC vs porocarcinoma. I favour BCC with poroid features over porocarcinoma. 

I think that the cellular stroma makes a BCC highly unlikely...it is actually making me think of a malignant tumor of hair follicle origin, even though porocarcinoma is also a good differential. Looking forward to finding out the diagnosis!

By the way, I am Carmen, a pathology resident from Romania and I am happy I am able to be part of this community! Thank you for sharing all these amazing cases!

Ciao Carmen, I’m Vincenzo from Italy, general pathologist.   

BCC vs. Porocarcinoma

Thanks for all the interesting dialogue on this case. This is a BCC with neuroendocrine differentiation. I did post a different example of this a few months ago. I think it is under-recognised, and can be spotted on routine sign out by areas of more typical BCC contrasting with a 'high grade' cytology. As far as the literature seems to indicate, the prognosis should be excellent i.e. minimal if any metastatic potential. But I still tend to have a slightly nervous feeling about this when signing out such cases and discussing at MDT meetings!

Some of the immunos are shown below. But in summary, BerEP4 is positive, EMA negative, as for BCC in general, expression of neuroendocine markers such as CD56, synaptophysin and chromogranin. CK20 was negative. Some do express CAM5.2, but without dot positivity. BW Saleem

Amazing case, Saleem. It hadn’t even occurred to me that might be a neuroendocrine variant. Thanks for the learning points. 

That's a nice case, Saleem. Thanks for sharing with us.

Just read a nice review of neuroendocrine tumours in Am J Derm Path Dec 2020