Case Number : Case 2434 - 31 October 2019 Posted By: Saleem Taibjee

Does the last figure show some ducts in this basaloid lesion?

yes basaloid cells with ducts and some what clear cytoplasm in the basaloid cells

Tumor of basaloid cells with mitoses, peripheral palisading and ulceration. Inflammatory infiltrate contains plasma cells which is a feature associated with ulceration of a BCC. Last but one picture shows stromal amyloid. I think it's a BCC although no retraction artifact is seen. 

CD34, BerEP4, EMA

Poroma with an unusual bcc-like peripheral component  

Found this in Kazakov book:....
strands of more basophilic cells resembling follicular germinative cells, palisaded at the periphery of the neoplastic nodules in the deeper portion or form- ing structures reminiscent of follicular germs. Even much rarer is the focal presence of stroma forming an abortive follicular papilla adjacent to the germ- like aggregations. These basaloid cells usually show abrupt transition from poroid cells, but occasion- ally, serial sections reveal a close admixture of poroid and basaloid cells....

Desmoplastic trichilemmoma

I thought about trichilemmoma but favor BCC - too basaloid for trichilemmoma.

Thanks for the interesting comments on this case. John Zhang's comments are extremely pertinent. 'Too basaloid for trichilemmoma'. Having recognised that trichilemmoma is a distinct possibility and a great mimick of BCC (clues on H&E; arises and blends from overlying epidermis (c.f. BCC is usually demarcated from the overlying epidermis), subtle clear cell change, peripheral palisading common to both, basement membrane-like material around lobules), it is then necessary to be aware of the particular pitfall of the 'basaloid variant' of trichilemmoma. a series of which we published last year: Turnbull et al. CD34 and BerEP4 Are Helpful to Distinguish Basaloid Tricholemmoma From Basal Cell Carcinoma. Am J Dermatopathol 2018;40:561–566.

For some reason, I have noticed that many general histopathologists and dermpath trainees seem to have a blindspot for trichilemmoma, particularly the desmoplastic and basaloid variants. Indeed going at speed, I was not too far off nearly reporting this case as BCC until paying attention to the H&E features above, and being aware of this basaloid variant pitfall.

Here is the confirmatory immunohistochemistry below (useful simple panel is CD34, BerEP4, EMA). CD34 will be positive in trichilemmoma, as clearly in this case (but may be only focal in some cases), whereas in BCC we find that BerEP4 will usually be diffusely positive (but rather minimal in this case) and EMA completely negative.

Have a good weekend. I'm about to settle down to watch the Rugby World Cup final.

BW 
Saleem

Good one Dr

Great case and comments Dr Saleem.

Good case. Thanks for sharing.