HISTORY: 61 yrs old female with rectal tumor with suspition of GIST was biopsied. Our diagnosis was: "sarcoma, most probably clear cell sarcoma vs MPNST". Wide resection eith anus was performed (photo attached).  
HISTO: Vague nodules of epithelioid and spindle cells with expansive border, spreading in mucosa, muscular wall, vaginal wall. Histologically seems "melanoma like": with focal hialynised areas, focal necrosis. Metastases in 3/30 perirectal nodes are present!  
IH: S100(+/++) 70%, Vimentin (+++) 100%, Asm Actin(-), PanCK(-)(single cells <5%+), Melan A/HMB45(-), EMA(-), CD117(-)(mastocytes +), Desmin(-), CD34(-)(neovascularity +), Ki67 50% (++), Cam5.2/CK7/CK19(-), CD57(-)(T lymphos +), CD56(+) 30%, NSE(+/+++) 70%, ER(-), CD31(+)(10% (meybr phoning), CD21/CD23/CD1a(-).  
MOLECS: EWSR break FISH in progress. Any fixed/known traslocations t(12;22) ir t(2;22) for clear cell sarcoma absent. BRAF mutation absent. C-kit ex9/11/13/17 mutations absent.  
 
PROPOSAL: Clear cell sarcoma (no translocations; S100+; HMB/Melan A(-)) vs MPNST (epithelioid)(S100+; CD56+; CD57(-)).  
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