Case Number : Case 2646 - 27 August 2020 Posted By: Saleem Taibjee

Epidermal hyperplasia with horn cysts and sebaceous glands looking like sebaceous nevus now showing basaloid proliferation and something like a trichelemmoma with mitosis

Coexistent Nevus sebaceous-associated and focally desmoplastic, trichilemmoma, trichiepithelioma and pigmented trichoblastoma. 

Nevus sebacous with basaloid proliferation, desmoplastic trichilemmoma and trichoblastoma.

Agree with @vincenzo

Please note the clinical photo. The main nodule is pearly with surface telangiectasia. There is a more subtle surrounding yellowish warty plaque within the scalp.

Here are the immunostains (I requested a limited panel only):

CD10 showed staining of the tumour epithelium (mainly peripheral staining pattern) within the larger basaloid nodule, and focal accentuation of staining in the stroma only. No evidence of Merkel cells within the main nodule (noting positive control of Merkel cells in the adjacent follicular infundibula and epidermis).

What's wrong with a BCC arising in a sebaceous naevus?  Thay's what it looks like clinically, and the CD10 staining is compatible.

4 hours ago, Richard Logan said:

What's wrong with a BCC arising in a sebaceous naevus?  Thay's what it looks like clinically, and the CD10 staining is compatible.

Agree... 

18 hours ago, Richard Logan said:

What's wrong with a BCC arising in a sebaceous naevus?  Thay's what it looks like clinically, and the CD10 staining is compatible.

Agree

can we tell that nevus sebaceous with basal cell carcinoma and trichelemmoma [ ? malignant]

Could it be a basaloid type of fSCC? ( ...I don’t know much about this pathology area ). 

Hi. This is a recent patient on whom I operated. The clinical photo shows a pearly nodule with telangiectasia suggestive of BCC, but there is a subtle adjacent yellow warty change.

For me this is an uncommon example of Basal cell carcinoma arising in naevus sebaceous. In the majority of cases we see trichoblastoma arising in NS, rather than BCC. However,  this is an uncommon exception. Features favouring BCC include the multifocal connection to overlying epidermis, tumour-derived amyloid, relative absence of stromal cell aggregates adjacent to tumour. The immunostains also support BCC in showing peripheral tumour staining with CD10 (as opposed to absent tumour staining, but mesenchymal staining in  trichoblastoma), and absence of Merkel cells. However, it is not possible to fully exclude 'hybrid' features. I did not show, but BerEP4 is strongly positive, EMA completely negative, and CD34 essentially negative, also supporting BCC rather than any of the differentials such as trichilemmoma, follicular SCC, etc.

Trichoblastoma (superficial areas) with BCC-like nodule. I've yet to see a convincingly "infiltrative or deeply invasive nodular BCC" in NS. These BCC-like nodular lesions are hard to distinguish from BCC and it's probably academic although would be nice if there was a reliable marker.