Case Number : CT0047 Adam_Bates

I'm thinking giant cell tumour of tendon sheath, with paucity of giant cells. I would ask for melanocytic markers to exclude clear cell sarcoma of soft tissue.
 

The presence of small pockets of spindle to oval cells with moderately abundant clear cytoplasm and slightly but definitely atypical oval nuclei with small prominent nucleoli are highly suggestive of clear cell sarcoma (soft tissue melanoma). Mitotic figures are not seen, as expected. Sparse multinucleated giant cells are also typical features.
 

My impression is sclerosing epithelioid fibrosarcoma...
 

Agree with Mona. It is sclerosing epithelioid fibrosarcoma. Neoplastic epithelioid cells with clear cytoplasm that are arranged in strands along densely hyalinized stroma form a typical picture of this variant of fibrosarcoma.
 

I called this giant cell tumor. It appears circumscribed to me. Melanocytic markers were negative. I did not think of a sclerosing epithelioid fibrosarcoma. I will pull the case again and take another look at it.
 

I watched this case with great interest yesterday. I was thinking giant cell tumour of tendon sheath rather than digital fibromatosis (Dupuytren's). Might have considered perineurioma, cellular digital fibroma (SAF group). I could not see the typical haemorrhage and osteoclast-type giant cells though and noted a slight epithelioid look to cells in upper right image. Clear cell sarcoma and sclerosing epithelioid sarcomd did not enter my thoughts (until reading the suggestions). I might have have run some immunos (EMA, S100, SMA, CD34, Macrophage) and then signed it out as benign favouring a tendon sheath tumour (assuming IHC unhelpful). As a rule odd variants of common things are still much more common than great rarities though I appreciate the ratio is often reversed on dermpathpro!
 

Regarding sclerosing epithelioid fibrosarcoma, as far as I can tell, neither cases arising in the fingers nor giant cells have been reported. And to quote Enzinger and Weiss "In almost all cases the tumor shows foci of spindle-shaped sarcoma similar to conventional fibrosarcoma." If still in doubt, I am told MUC4 is positive in four fifths of cases.