Case Number : Case 2591 - 11 June 2020 Posted By: Saleem Taibjee

MAC

I am thinking of both DT and MAC. There are keratin cysts as well as duct formation and infiltration into the subcutaneous fat with desmoplastic stroma...not able to further differentiate these both. 
There are no obvious BCC like nests.

 Thank you for this case learning.... waiting to learn some important points

MAC

Favor DTE. I don’t see any perineurial infiltration, and  there are calcifications. 

some mitotic activity seen favor MAC

For me, MAC is not a suitable diagnosis for this superficial tumor. DTE with ductal differantiation is a more appropriate diagnosis for this superficial tumor. 

Thanks for the interesting comments.

I attach the immunohistochemistry below.

As you can see, BerEP4 was clearly positive, EMA negative, and CEA highlights the ducts evident on H&E.

This immunoprofile is a good fit for a rare example of infiltrative BCC showing ductal differentiation.

I have not come across Desmoplastic trichoepithelioma showing ductal differentiation, but can see that would be a reasonable differential diagnosis. That said, the tumour showed mitoses, as shown in the images below, and apoptotic bodies were also relatively easy to find. There is also an impression of interstitial mucin in addition to the sclerotic stroma. The tumour extends relatively deeply to the interface of dermis and subcutis. One could also request a CK20 to assess for Merkel cells, but these were not readily seen on the EMA in any case. I think overall this constellation tends to favour BCC rather than DTE. I don’t think the case is such a good fit for MAC.

and here the mitoses ....

Thanks, Saleem. I didn’t see apoptotic bodies, because many times we( I ) don’t see what we( I ) don’t want to see!

Nice case!