Percutaneous Renal Biopsies for Small Renal Masses: Complex Tumors on Nephrometry Should Be the First Targets

Abstract Objective To assess the diagnostic yield, accuracy, and complications rate for computed tomography (CT)-guided renal biopsies for solid renal masses (SRM); to analyze predictive factors for diagnostic biopsies. Patients and Methods We performed a single-center, retrospective study based on a pathologic database query for CT-guided, percutaneous renal biopsies. Inclusion criteria included presence of SRM; exclusion criteria included the presence of metastases, non-cT1a or higher cancer (> 4 cm), and non-CT-guided techniques. Of 119 patients who underwent renal biopsies, 40 (34%) were excluded from the study; 79 (66%) biopsy outcomes were analyzed. Clinical, radiologic (RENAL score), and pathologic features were reported. Differences between contributive and noncontributive biopsies were tested with Mann-Whitney U or chi-square tests, as appropriate. Multiple-variable analyses searching for predicting factors of biopsy contribution were performed with binary logistic regressions. Results CT-guided renal biopsies for SRM present a high yield (88.6%) and high accuracy for differentiating malignant from benign tumors (96%). They are less accurate for histologic subtype (93%) and unreliable for Fuhrman grading (64%). CT-guided renal biopsy is safe (minor complication rate, 2.5%) and helped prevent unnecessary surgery in 30.4% of the cohort. Tumor complexity with high RENAL score was a predictive factor ( P  = .02) of contributive biopsy. Conclusion SRM biopsy is a safe, reliable procedure that can help determine the best treatment strategy for patients. It seems more beneficial for nephrometry complex tumors when surgical extirpation is more likely to be complicated. SRM biopsy might be encouraged in clinical practice for complex tumors.