Case Number : Case 2061 - 1 May 2018 Posted By: Uma Sundram

A difficult case! ?metastatic Merkel cell carcinoma(lymphovascular infiltration in pic1)...? metastatic prostatic carcinoma ( lymphovascular infiltration in pic1 )...?Sebaceous carcinoma(poorly differentiated type)...?metastatic melanoma(last but not least).

Merkel for me

Poorly diff Sebaceous ca 

Very difficult to come to a single diagnosis. The list of small blue cell tumors is too exhaustive!

Agreed that this is tough. I favored merkel cell carcinoma because: 1) it was a cohesive, rather than discohesive, infiltrate, which somewhat argues against melanoma and lymphoma; 2) no real squamous differentiation was seen; the histologic features of BCC were not present (although that can be tricky); 3) on high power examination, it seemed more like a neuroendocrine tumor. The pictures don't project well but Figure 2 seems particularly convincing. Sebaceous carcinoma, an unusual cutaneous adnexal carcinoma, and metastatic adenocarcinoma were all in the differential.

The tumor cells express both CK20 and CKAE1 in a perinuclear 'dot like' pattern, suggesting Merkel cell carcinoma. TTF1 and CK7 were negative.

Well done Raul. 

Late, but I thought too of Merkel!

Nice case!

looks quite small round/blue cell tumor.