Algorithm-Based Approach to the Histological Routine Diagnosis of Renal Oncocytic Tumors in Core Biopsy Specimens

Purpose of Review A growing number of tumor entities with badly defined limits are enlarging in the last years the family of oncocytic tumors in the kidney. Recent Findings Chromophobe renal cell carcinoma (ChRCC) and renal oncocytoma (RO) are classically well-known tumors, but the borderland between them, and their precise connection, remains a matter of debate. Aside from that, other emerging and provisional entities, like eosinophilic solid and cystic renal cell carcinoma (ESC RCC), eosinophilic vacuolated tumor (EVT), low-grade oncocytic tumor (LOT), and papillary renal neoplasm with reverse polarity (PRRP), have been recently described. This spectrum of tumors remains a diagnostic challenge in renal pathology, especially if the specimen obtained is scarce. Summary This review focuses on practical diagnostic problems when managing core biopsies and proposes a diagnostic algorithm maximizing the information provided by both morphology and immunohistochemistry. So, a combination of morphologic features on hematoxylin-eosin and six antibodies (CK7, CD117, CK20, CD10, GATA-3, and cathepsin K) is advised to be used in a stepwise fashion.