Oncocytoma

Oncocytoma is the most important benign renal tumor. It originates from intercalated cells of the tubules. The name comes from the tumor cells are oncocytes, cells with large eosinophilic cytoplasm due to high content of mitochondria. The tumor is brownish on macroscopy. It can be hard to distinguish from chromophobe renal cell carcinoma, for which we must use cytogenetics. In most cases, oncocytoma is suspected to be RCC and is therefore treated as it. It may also transform into oncocytic RCC.