Renal Mass Biopsy

Renal mass biopsy is gaining acceptance, especially as a tool in the diagnostic algorithm of small renal masses as currently advised in the major kidney tumor/renal cell carcinoma guidelines. Both core biopsy or fine needle aspiration (FNA) can be performed with CT or ultrasound guidance, depending on tumor visualization and setting. The interpretation of results is confounded by the use of different nomenclatures, the heterogeneity of the series, and lack of a uniform standard for comparison. Besides a full body of literature, several systematic reviews show that the pooled nondiagnostic rate is low (8–14%) and that sensitivity and specificity in distinguishing malign from benign tumors is 98% and 95%, respectively. However, negative predictive value remains low at 63% when biopsy results are compared with the surgical specimen. Those results are slightly lower when FNA is considered. Concordance between biopsy and surgical specimen is good/substantial for subtype determination but remains fair for grade determination with a concordance for grade of 63%. Complications after renal mass biopsy are rare and present in up to 8% of patients. The most common complication is perinephric hematoma (5%), although only 1% of patients require transfusion. Lastly biopsy is strongly recommended prior to or during renal mass ablation, not only for diagnostic purposes but also to adapt follow-up.