title: Renal oncocytoma: multifocality, bilateralism, metachronous tumor development and coexistent renal cell carcinoma.
abstract: OBJECTIVE
  We analyzed a large series of cases of renal oncocytoma to define the incidence of coexistent renal cell carcinoma, multifocality, bilateralism and metachronous tumor development.
  
  
  METHODS
  Between 1980 and 1997, 100 men and 38 women with a mean age of 68 years with oncocytoma, were treated surgically at our institution. We analyzed tumor characteristics and reviewed specimens for coexistent 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 ranged from 0.3 to 14.5 cm. (median 3.2). Oncocytoma was unilateral in 131 cases (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%) metachronous oncocytoma developed during followup. No patient had locally recurrent oncocytoma after partial nephrectomy for a solitary renal oncocytoma. Renal cell carcinoma and oncocytoma were found in 14 patients (10%), including unilateral synchronous disease in 9 and bilateral synchronous disease in 5.
  
  
  CONCLUSIONS
  Our data support the benign nature of renal oncocytoma. Multifocality, bilateralism and metachronous tumor develop in approximately 4 to 6% of all cases. Renal cell carcinoma coexisted in 10% of oncocytoma cases.
authors.affiliation: Department of Urology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Dechet
authors.forename: D G
authors.initials: DG
authors.lastname: Bostwick
authors.forename: M L
authors.initials: ML
authors.lastname: Blute
authors.forename: S C
authors.initials: SC
authors.lastname: Bryant
authors.forename: H
authors.initials: H
authors.lastname: Zincke
mesh_terms: D018249:Adenoma, Oxyphilic / Q000453:epidemiology* / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000453:epidemiology* / Q000473:pathology; D005260:Female; D006801:Humans; D015994:Incidence; D007680:Kidney Neoplasms / Q000453:epidemiology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009378:Neoplasms, Multiple Primary / Q000453:epidemiology* / Q000473:pathology