Case Number : Case 3041 - 03 March 2022 Posted By: Saleem Taibjee

Epithelioid blue nevus VS PEM. Those large "RS-like" cells with prominent nucleoli are expected in PEM. PRKAR1A status for confirmation.

Cellular/epithelioid blue naevus.

PEM

On 03/03/2022 at 02:20, Shawn said:

Epithelioid blue nevus VS PEM. Those large "RS-like" cells with prominent nucleoli are expected in PEM. PRKAR1A status for confirmation.

Agree

Favor PEM. Thought of DPN also, but, as pointed out by Shawn, RS-like cells are definitely in keeping with PEM. 

Challenging. The entire gamut of epithelioid blue nevus, PEM and BLITZ (Blue+Sptiz) or called as superficial variant of DPN by some, are overlapping. PRAKAR1 and Beta-Catenin will be helpful. 

Yes, very well done. This is indeed pigmented epithelioid melanocytoma.

This case had already been signed out by another pathologist as blue naevus. I reviewed this case prior to MDT, when the small focus of epithelioid cells which show prominent nucleoi - 'fried eggs' - caught my attention, and which are highlighted above.

You can appreciate my excitement when I learned at the MDT that the patient has facial freckling and other pigmented lesions, and a history of angiomyxoma of the vulva previously, and the clinician was suspecting Carney complex. This information had not appeared on the original clinical request form. But, of course, on discovering this information, this puts this lesion more firmly into the PEM category. These are lesions which historically were called epithelioid blue naevus in the context of Carney, but this is no longer the appropriate term.

I show the Melan-A and S100 below. The Melan-A makes the fried egg cells really 'pop out'. The S100 also stains quite strongly. As you know this is indirect evidence that this is not a blue naevus (in which S100 is often diminished).

I have since heard that the patient now has genetically confirmed Carney complex.

I don't have access to IHC / tissue testing for PRKAR1A, and so have sent this case on to Arnaud de la Fouchardiere in Lyon; he has also confirmed loss of PRKAR1A on IHC.

BW
Saleem

Great case, Saleem. And many learning points. Thanks.