title: Renal Tumor Biopsy for Small Renal Masses: A Single-center 13-year Experience.
abstract: BACKGROUND
  Renal tumor biopsy (RTB) for the characterization of small renal masses (SRMs) has not been widely adopted despite reported safety and accuracy. Without pretreatment biopsy, patients with benign tumors are frequently overtreated.
  
  
  OBJECTIVE
  To assess the diagnostic rate of RTBs, to determine their concordance with surgical pathology, and to assess their impact on management.
  
  
  METHODS
  This is a single-institution retrospective study of 529 patients with biopsied solid SRMs ≤4 cm in diameter. RTBs were performed to aid in clinical management.
  
  
  METHODS
  Diagnostic and concordance rates were presented using proportions. Factors that contributed to a diagnostic biopsy were identified using a multivariable logistic regression.
  
  
  CONCLUSIONS
  The first biopsy was diagnostic in 90% (n=476) of cases. Of the nondiagnostic biopsies, 24 patients underwent a second biopsy of which 83% were diagnostic. When both were combined, RTBs yielded an overall diagnostic rate of 94%. Following RTB, treatment could have been avoided in at least 26% of cases because the lesion was benign. Tumor size and exophytic location were significantly associated with biopsy outcome. RTB histology and nuclear grade were highly concordant with final pathology (93% and 94%, respectively). Adverse events were low (8.5%) and were all self-limited with the exception of one. Although excellent concordance between RTB and final pathology was observed, only a subset of patients underwent surgery following biopsy. Thus it is possible that some patients were misdiagnosed.
  
  
  CONCLUSIONS
  RTB of SRMs provided a high rate of diagnostic accuracy, and more than a quarter were benign. Routine RTB for SRMs informs treatment decisions and diminishes unnecessary intervention. Our results support its systematic use and suggest that a change in clinical paradigm should be considered.
  
  
  RESULTS
  Renal tumor biopsy (RTB) for pretreatment identification of the pathology of small renal masses (SRMs) is safe and reliable and decreases unnecessary treatment. Routine RTB should be considered in all patients with an indeterminate SRM for which treatment is being considered.
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 Medical Imaging, Toronto General Hospital, University Health Network and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: John R
authors.initials: JR
authors.lastname: Kachura
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; Division of Urology, Department of Surgery, Mount Sinai Hospital and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Alexandre R
authors.initials: AR
authors.lastname: Zlotta
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: Thomas
authors.initials: T
authors.lastname: Hermanns
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: Tristan
authors.initials: T
authors.lastname: Juvet
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: D000368:Aged; D001706:Biopsy; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors; D047368:Tumor Burden
keywords: Renal cell carcinoma; Renal tumor biopsies; Small renal mass