MTOR and renal cell carcinoma: In this morphological scenario, cathepsin-K (clone 3F9) is a useful tool for differentiating renal oncocytoma, chromophobe RCC, and LOT which are negative for cathepsin-K (clone 3F9), from ESC-RCC, EVT, and mTOR-mutated eosinophilic RCC which are positive for this marker [28].