Case Number : Case 1975 - 27 Dec 2017 Posted By: Limin Yu

No clefts or mucin/amyloid stromal changes. A cellular, specialized peritumoral stroma with some subtle PMB-appearance...and with demarcation from the surrounding dermis. I think this lesion is in the Trichoblastoma\Trichoepithelioma spectrum. I'd like to call this superficial TB.

Agree with Vincenzo- trichoblastoma

Cutaneous lymphadenoma. A type of trichoblastoma.

Favour BCC. I have a personal adage that for every time you think of TE/TB on the central face in a patient of this age (>50y) it's a BCC >19 times out of 20. Obviously normal rules don't necessarily apply in dermpathpro but for me the tumour is strongly favoured to be a BCC on morphological gounds in any case. You could do CK20, CD10 - I find it quite helpful but not sure I'd have bothered on this case as the lesion appears small and out in any case (on these images). I like the little leaping dog!

I'd also be interested in the BerEP4 pattern (my cutaneous lymphadenomas have had rather distinctive peripheral staining only (unpublished), that would be very uncommon for a BCC, I demonstrated reactive Merkel cells in one cutaneous lymphadenoma but only photographed it on one case it appears). Cutaneous lymphadenomas are pretty rare so a small collection with IHC would be of interest for publication.

I like BCC too, and probably would not have gone down any other road. I find CK20 to be helpful in difficult cases.

Looks like a Trichoepithelioma but I would also like to see a CK20

I favor adamantinoid trichoblastoma based on morphology. If it is a new lesion in a 56 year old BCC is more likely, but if it is a lesion with 20 year history it can certainly be trichoblastoma. 

At first, I apologize for overlooking this case and not providing the feedback in a timely manner. This case was posted during Christmas break and fell through the cracks.  That wasn't my excuse -- my apologies. 

Your insightful discussion reflects my debate with myself. This is a circumscribed basaloid neoplasm. My first impression was to call it BCC. Something bothered me and stopped me from signing it our as a BCC. The stromal  changes are more fibrotic than what's usually seen in BCC. I finally called it cutaneous lymphadenoma, which is type of trichoblastoma.  Your points are well-taken. And I don't believe there are reliable histologic features distinguishing BCC from TB/TE. This case underscores the hypothesis that some BCC and TE/TB are in the same spectrum.