Safety, reliability and accuracy of small renal tumour biopsies: results from a multi‐institution registry

Objective To validate, in a multi‐institution review, the safety, accuracy and reliability of renal tumour biopsy ( RTB ) and its role in decreasing unnecessary treatment. Materials and Methods We conducted a multi‐institution retrospective study of patients who underwent RTB to characterize a small renal mass ( SRM ) between 2011 and May 2015. Patients were identified using the prospectively maintained Canadian Kidney Cancer information system. Diagnostic and concordance rates were presented using proportions, whereas factors associated with a diagnostic RTB were identified using a logistic regression model. Results Of the 373 biopsied SRM s, the initial biopsy was diagnostic in 87% of cases. Of the 47 non‐diagnostic biopsies, 15 had a repeat biopsy of which, 80% were diagnostic. When both were combined, therefore, a diagnosis was obtained in 91% of SRM s. Of these, 18% were benign. Size was the only factor found to be associated with achieving a diagnostic biopsy. RTB histology and nuclear grade (high or low) were found to be highly concordant with surgical pathology (86 and 81%, respectively). Of the discordant tumours ( n = 16), all were upgraded from low to high grade on surgical pathology. Adverse events were rare (<1% of cases). Conclusion The present multi‐institution study confirms that RTB of SRM s is safe, accurate and reliable across institutions, while decreasing unnecessary treatment. Given our findings, RTB s may be a helpful tool with which to triage SRM s and guide appropriate management.