Case Number : Case 2606 - 02 July 2020 Posted By: Saleem Taibjee

Clear Cell Sarcoma of Soft Parts. Nice fibrovascular septal organization. And nice nucleolar prominence. 

Cellular blue naevus?

Agree with clear cell sarcoma

Clear cell sarcoma

Clear cell sarcoma

Clear cell sarcoma

Clear cell sarcoma

Sorry for the delay on this case.

Yes this is indeed Clear Cell sarcoma.

As Vincenzo points out, the prominent fibrous septae are a good clue, as well prominent nucleoli. I could not identify wreath like giant cells (an additional clue) despite careful scrutiny.

As you probably all know, immunohistochemistry isn't so helpful in such cases, because clear cell sarcoma is often positive for melanocytic markers.

EWSR1 rearrangement was confirmed in this case, supporting the diagnosis.

Saleem, are the cells dissecting the collagen in the upper dermis also part of the tumour, as they look so different?

I think these are tumour cells also. I was reading that occasionally clear cell sarcoma can include a superficial component, and even a junctional/pseudo-junctional component, adding to the potential for misdiagnosis as melanocytic.