Update on oncocytoma.

Oncocytoma is the most common benign solid renal tumor, comprising roughly 5% of resected renal masses. Typically discovered incidentally, oncocytoma is generally asymptomatic and very rarely metastasizes; however, multifocal disease and coexistence with renal cell carcinoma can occur. No currently used imaging techniques can reliably distinguish between oncocytoma and malignant lesions; therefore, patients must undergo resection, or in certain circumstances, biopsy, to definitively establish diagnosis. Careful attention to pathologic features and the adjunctive use of immunostains can aid in discriminating oncocytoma from other renal tumors characterized by granular, eosinophilic cytoplasm, especially chromophobe renal cell carcinoma. Nephron-sparing and laparoscopic surgical approaches can be used to treat appropriately selected patients.