Case Number : Case 2075 - 21 May 2018 Posted By: Limin Yu

Trichoepithelioma (racemiform trichoblastoma)

Difficult case of adnexal cutaneous tumor. It looks like a trichifolliculoma, but my first spot is of INFUNDIBULOCYSTIC BCC. There is an epithelial stromal retraction and a myxoid stroma. 

Pigmented trichoblastoma

pigmented infundibulocystic (organoid) basal cell carcinoma. 

IFC BCC vs Basaloid follicular hamartoma 

The best diagnosis in BCC (infundibulocystic/TE-like). Remember TE tend to have about 50% stroma c/w epithelium this case is more like 70:30 infavour of epithelium. Also no papillary mesenchymal cells to my eye in these images. My "limited" IHC of choice CD10 (epithelium predominant supports BCC while stromal predominant supports TE) and CK20 (30% of TE have numerous reactive dendritic Merkel cells). Also at this age you will see probably 20+ TE-like BCC for every TE.

Thank everyone for the insightful discussion. It is a "tough" case, both TE and BCC are in the differential diagnosis. My vote is that this is a BCC (infundibulocystic growth pattern).