Case Number : Case 4024 - 23 June 2022 Posted By: Saleem Taibjee

Trichoepithelioma

Rippled pattern Trichoep/Trichoblastoma.

Trichoepithelioma/Trichoblastoma.

Trichoblastoma, stromal clefts, papillary-mesenchimal cells, scattered Lc

At that age not common, unless nevus sebaceous association

aslo CYLD gene mutation Brooke-spiegler syndrom association

Trichoblastoma. 

Does anyone have any comments/thoughts about the cytology (before I give my response)?

BW, Saleem

The cytology looks like the blastic features well described in old books about tricho”blastoma”. Trichoepithelioma shows more mature, basaloid features. Am I wrong?

Used blastoid instead germinal, because , in this case, there might be confusion with the trichogerminoma variant ( squamoid morules ). 

So I agree with trichoblastoma. But having seen regular examples of BCC with neuroendocrine differentiation, this case immediately struck me as showing a similar cytology with large relatively nuclei with dispersed chromatin.

The immunos are shown below. There is positive staining for neurofilament, and patchy staining for CD56, focal chromogranin (negative for synaptophysin). CK20 was negative, in fact not even showing entrapped Merkel cells which we might see in trichoblastoma. CD10 nicely highlighted the aggregates of papillary mesenchymal cells, but also showed some staining of the tumour epithelium.

I have trawled through the literature, and this seems to be a very rare occurrence. I found one reference to a trichilemmal carcinoma with neuroendocrine differentation, but not a whole lot else. Has anyone else come across this? But perhaps it is more common than we appreciate... We plan to write up the case.

BW. Saleem