title: Active Surveillance for Renal Neoplasms with Oncocytic Features is Safe.
abstract: OBJECTIVE
  Oncocytomas are benign tumors often diagnosed incidentally on imaging. Small case series have suggested that the growth kinetics of oncocytomas are similar to those of malignant renal tumors. Biopsy material may be insufficient to exclude a diagnosis of chromophobe renal cell carcinoma. We evaluated and compared the growth rates of oncocytoma and chromophobe renal cell carcinoma to improve our understanding of their natural history.
  
  
  METHODS
  This was a single center, retrospective study of patients diagnosed with lesions suggestive of oncocytoma or chromophobe renal cell carcinoma between 2003 and 2014. The growth rates were estimated using a mixed effect linear model. Patient and lesion characteristics were tested using a similar model for association with growth rate.
  
  
  RESULTS
  Of the 95 lesions (oncocytoma 81, chromophobe renal cell carcinoma 14) included in the analysis 98% were diagnosed on biopsy. The annual growth rate was 0.14 cm and 0.38 cm for oncocytoma (median followup 34 months) and chromophobe renal cell carcinoma (median followup 25 months), respectively (p=0.5). Baseline lesion size was significantly associated with growth (p <0.001). The majority of oncocytomas (74%) and chromophobe renal cell carcinomas (67%) followed up to the 3-year mark had grown. Of these, 8 underwent surgery (6 in the chromophobe renal cell carcinoma group). The initial diagnosis was confirmed in all. Overall 5 patients died, all of nonrenal related causes.
  
  
  CONCLUSIONS
  Although the majority of oncocytic renal neoplasms will grow with time, surveillance appears to remain safe. Patients opting for this strategy should be made aware that a diagnosis of oncocytoma following biopsy is associated with some degree of uncertainty due to the difficulty of differentiating them from other oncocytic renal neoplasms.
authors.affiliation: Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Patrick O
authors.initials: PO
authors.lastname: Richard
authors.affiliation: Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Michael A S
authors.initials: MA
authors.lastname: Jewett
authors.affiliation: Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jaimin R
authors.initials: JR
authors.lastname: Bhatt
authors.affiliation: Department of Laboratory Medicine and Pathobiology, Toronto General Hospital, University Health Network and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Evans
authors.affiliation: Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Narhari
authors.initials: N
authors.lastname: Timilsina
authors.affiliation: Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, Toronto, Ontario, Canada. Electronic address: antonio.finelli@uhn.ca.
authors.forename: Antonio
authors.initials: A
authors.lastname: Finelli
mesh_terms: D018249:Adenoma, Oxyphilic / Q000473:pathology* / Q000628:therapy*; D002292:Carcinoma, Renal Cell / Q000473:pathology* / Q000628:therapy*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology* / Q000628:therapy*; D008297:Male; D061214:Patient Safety; D012189:Retrospective Studies; D057832:Watchful Waiting
keywords: biopsy; carcinoma; growth; oncocytoma; renal; renal cell