Case Number : Case 2301 - 9 April 2019 Posted By: Uma Sundram

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Malignant (cellular atypia, infiltrative borders) epithelioid neoplasm. My differential diagnoses include metastatic carcinoma (due to limited connection to the epidermis), primary cutaneous squamous cell carcinoma (I can almost see a hint of intercellular bridges), or a melanoma. I would obtain history, p63, S100 and Mart1. Other opinions please.

Agree with the differential.

I favor Melanoma because there is an intraepithelial component (i think). Also, de dermis look quite fibrotic. Could be a recurrence?

Cells have spitzoid morphology- I would consider BAP-1 inactivated melanocytic tumor

Great comments! We too favored melanoma but thought it was a difficult case. The patient has no other history of melanoma and this is not a recurrence to our knowledge. CGH had a complex series of chromosomal changes, and BAP1 was retained.

S100 and MART1 were both positive.

I'd be holding back as I can't see dermal mitosis. There is a slightly lentiginous prolieration in the junction. STUMP, p16, HMB45, patterns of melanA, Ki67, BRAF VE1. If these don't resolve may have to consider the next steps as a patient would get a SLNBx if its not Spitz Group. MBAIT are usually combined but would be reasonable to consider. 

Apologies to Uma I think I must have mis-read the comment about CGH which is clearly supportive of malignant diagnosis. Although I'm also wondering if we were posting simultaneously!