Case Number : Case 2005 - 12 Feb 2018 Posted By: Limin Yu

favor basal cell carcinoma

Agree. Strongly in favour of a rather indolent appearing nodular BCC (trichoepithelioma-like). CD10 (epithelial dominant staining), CK20 (reactive Merkel cells limited to trapped follicles only) and BerEP4 (diffuse & strong throughout sparing only central keratocysts) can be helpful.

Infundibulocystic BCC? Kind of big to consider basaloid follicular hamartoma.

Agree with BCC.

What do the pale pink cells suggest? Can we call it a BCC with isthmic differentiation?

Thank everyone!  I signed out this case as an Infundibulocystic BCC. TE is a close ddx.

Nice case!

 Yes agree. I call them Infundibulocytic BCC (when tumorous and large as pointed above). There are others who shy away from the term as the number of infundibular cysts are variable and sometimes scant but the circumscription, central eosinophilic cords and peripheral basaloid nubbins are suggestive (for me). If I remember correctly Dr Ackerman's in his book on follicular tumors says these can even have papillary mesenchymal bodies and absence of clefts. 
In smaller lesions basaloid follicular hamartomas is a d/d. 
Infundibulocystic BCC are most often sporadic; however its is a variant associated with Gorlin syndrome or the multiple hereditary infundibulocytic basal cell carcinoma syndrome.  

On ‎14‎/‎02‎/‎2018 at 06:55, Anil Patki said:

What do the pale pink cells suggest? Can we call it a BCC with isthmic differentiation?

Dear Anil,

I don't see why not.

More generally I personally prefer nodular ("infundibulo-cystic" or "TE-like" I only mention to my friends as I prefer not confuse the clinical colleagues) BCC's and have observed that they are very much more commonly located in the nasolabial and delicate areas of the face. I have seen several examples mis-reported as trichoepitheliomas. Remember I have said previously every time you want to diagnose a TE in a patient >50y on the face 19 of 20 cases will be BCC. I don't think I have seen convincing papillary mesenchymal cells in this variant of BCC and a big clue is that they are almost always >80% epithelial compared with TE (that almost always do have PMCs) that are usually 50:50 stroma:epithelium (usually with stromal clefts). If in doubt have it excised with narrow margins. I've seen these wrongly reported very indolent lesions deep in the facial muscles by the time the penny dropped. Also stromal keratin derived amyloid is not stroma so watch out for that too in these lesions.

Thanks Richard for the elaborate exposition