RCCFMS is short for renal cell carcinoma with fibromyomatous stroma. The top ddx are clear cell RCC and ELOC-mutated RCC. RCCFMS showed cup CAIX similar in clear cell papillary renal cell tumor. A key part of the panel is that clear cell RCC is negative for CK7 and both ELOC and RCCFMS showed some positivity for CK7.
What WHO says if you can't do molecular?
"clear cell RCCs with prominent fibromuscular septations and CK7 positivity, and give a differential diagnosis"
Pictures credit: Ren Dong, MD, PGY-3, UC Irvine.
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