Renal tumor biopsies for evaluation of small renal tumors: why, in whom, and how?

CONTEXT: Renal tumor biopsies (RTBs) gained popularity in the evaluation of small renal tumors (SRTs) because imaging alone is insufficient to show the underlying aggressiveness of SRTs and more ablative therapies without definitive histology are available.
OBJECTIVE: To describe why, in whom, and how RTB should be performed for the evaluation of SRTs. EVIDENCE ACQUISITION: Data were obtained from English-language studies on the use of RTB for the evaluation of solid SRTs in vivo listed in PubMed. EVIDENCE SYNTHESIS: The reasons for RTBs are (1) the increasing incidence of SRTs; (2) the finding that a significant number of SRTs (20%) are benign; (3) the availability of new management options, such as ablative therapy and surveillance strategies; and (4) the fact that imaging alone is unable to predict biologic behavior. In addition, advances in pathologic evaluation have improved the ability of RTB to differentiate the underlying tumor. Three studies of RTB for SRTs in vivo performed under computed tomography (CT) guidance together with a complete histopathologic evaluation gave accuracies for predicting malignancy, grading, and renal cell cancer subtype of 92-96%, 70-76%, and 78-92%, respectively. RTB was insufficient or inconclusive in 3-21% of cases. RTB was underutilized in ablative therapies of SRT (20-45% had no or inconclusive histology). The use of RTB was limited in multiple renal tumors and hybrid tumors. The complication rate was low (<5%), major complications were very rare (<1%), and tumor spreading has been reported only anecdotally. RTB are recommended to help in differentiating benign from malignant SRTs prior or during ablative therapies and in follow-up, especially after radiofrequency (RF) ablation.
CONCLUSIONS: RTB is a safe and accurate procedure by which to evaluate SRTs. RTB can help in defining patient management-especially the use of ablative surgery-and to find benign renal tumors.