Renal oncocytoma treated by surgical enucleation: a case report.

We experienced a case of renal oncocytoma, in a 46-year-old woman. At a health examination, ultrasonography revealed a right renal tumor, and she was admitted to our hospital for evaluation. From the ultrasonogram, computerized tomography (CT) and angiography, we suspected a renal oncocytoma, but renal cell carcinoma was not completely ruled out. Since the location of the tumor seemed suitable for a local resection, we scheduled a surgical enucleation, but we intended to switch to a radical nephrectomy if examination of a frozen-section suggested renal cancer. Because the frozen findings were suggestive of an oncocytoma without malignancy, the surgical enucleation procedure was completed as scheduled. Pathological findings of the resected specimens were characterized by granular eosinophilic cytoplasm, and rounded nuclei without nuclear pleomorphism or mitotic figures. Electron microscopic studies revealed an increased number of mitochondria. The patient was accordingly diagnosed as having renal oncocytoma. We also reviewed the literature to elaborate procedures for a preoperative diagnosis and therapy for renal oncocytoma.