title: Renal oncocytoma growth rates before intervention.
abstract: OBJECTIVE
  To describe the growth rates of oncocytomas before treatment with surgical resection or percutaneous ablation.
  
  
  METHODS
  This single-institution retrospective study included 33 consecutive, pathologically proven renal oncocytomas with serial contrast-enhanced computed tomography scans spanning at least 1 year before intervention, from 2000 to 2009. Tumours were measured by two radiologists, and growth rates and interobserver variability were calculated. The mean (range) pre-procedural imaging surveillance period was 36 (12-124) months (median 33 months).
  
  
  RESULTS
  The mean (SD) oncocytoma size was 17 (11) mm (range 4-47 mm, median 15 mm) in maximum transverse diameter on initial imaging and grew to a mean (SD) of 26 (5) mm (range 10-83 mm, median 23 mm) by the time of treatment. Overall, the mean (SD) and median growth rates were 2.9 (2.6) mm/year and 2.7 mm/year, respectively (range -1.2-10.9 mm/year). After weighting by the se of each tumour's growth rate, the mean (SD) change was 2.1 (1.2) mm/year. The mean (range) interobserver variability for each tumour measurement was 1 (0-7) mm with an intraclass correlation coefficient of 0.99.
  
  
  CONCLUSIONS
  Renal oncocytomas grow at a rate similar to reported growth rates of renal cell carcinoma. As the observation of growth does not distinguish between benign and malignant renal tumours, growth of small renal masses under active surveillance should be carefully considered before a switch is made to intervention.
authors.affiliation: Departments of Radiology, Mayo Clinic, Rochester, MN 55902, USA. kurup.anil@mayo.edu
authors.forename: Anil Nicholas
authors.initials: AN
authors.lastname: Kurup
authors.forename: R Houston
authors.initials: RH
authors.lastname: Thompson
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Leibovich
authors.forename: W Scott
authors.initials: WS
authors.lastname: Harmsen
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Sebo
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Callstrom
authors.forename: Akira
authors.initials: A
authors.lastname: Kawashima
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Atwell
mesh_terms: D018249:Adenoma, Oxyphilic / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000175:diagnosis; D017115:Catheter Ablation; D003452:Cryosurgery; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D010535:Laparoscopy; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy; D014057:Tomography, X-Ray Computed