Renal oncocytoma: Multifocality, bilateralism, metachronous tumor development and coexistent renal cell carcinoma

Purpose: We analyzed a large series of cases of renal oncocytoma to define the incidence of coexistent renal cell carcinoma, multifocality, bilaterali sm and metachronous tumor development. Materials and Methods: Between 1980 and 1997, 100 men and 38 women with a m ean age of 68 years with oncocytoma, were treated surgically at oar institu tion. We analyzed tumor characteristics and reviewed specimens for coexiste nt renal cell carcinoma. Results: Tumors were discovered incidentally in 58% of the cases. Specimens were obtained from 84 radical and 70 partial nephrectomies. Tumor size ran ged from 0.3 to 14.5 cm. (median 3.2). Oncocytoma was unilateral in 131 cas es (95%) and bilateral in 7 (5%), while there were multiple oncocytomas in 8 (6%). Mean followup was 41 months (range 0 to 200). The disease specific survival rate was 100% and no patient had metastasis. In 6 patients (4%) me tachronous oncocytoma developed during followup. No patient had locally rec urrent oncocytoma after partial nephrectomy for a solitary renal oncocytoma . Renal cell carcinoma and oncocytoma were found in 14 patients (10%), incl uding unilateral synchronous disease in 9 and bilateral synchronous disease in 5. Conclusions: Our data support the benign nature of renal oncocytoma. Multif ocality, bilateralism and metachronous tumor develop in approximately 4 to 6% of all cases. Renal cell carcinoma coexisted in 10% of oncocytoma cases.