Renal tumor biopsy for small renal masses: a single-center 13-year experience

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. DESIGN, SETTING, AND PARTICIPANTS: This is a single-institution retrospective study of 529 patients with biopsied solid SRMs ≤4cm in diameter. RTBs were performed to aid in clinical management. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Diagnostic and concordance rates were presented using proportions. Factors that contributed to a diagnostic biopsy were identified using a multivariable logistic regression. RESULTS AND LIMITATIONS: 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. PATIENT SUMMARY: 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