Accuracy and implications of percutaneous renal biopsy in the management of renal masses.

INTRODUCTION Percutaneous renal biopsy in patients with renal masses is increasing. We investigated the accuracy of percutaneous renal mass biopsy results in patients undergoing evaluation of solid renal masses. METHODS A retrospective review was performed of patients in the Kaiser Permanente Southern California Region who underwent computed tomography or ultrasound-guided percutaneous renal biopsy of a solid renal mass between January 2005 and December 2009. Patients were stratified by size of mass (≤ 4 cm vs > 4 cm). Initial biopsy results were correlated with final pathology specimens after extirpation. RESULTS Medical records of 126 patients (129 renal units with 132 biopsies) were reviewed. Initial diagnostic biopsies revealed 87 (66%) malignant, 38 (29%) benign, and 7 (5%) nondiagnostic lesions. Sixty-three patients (50%) ultimately underwent extirpative surgery (23 partial and 40 radical nephrectomies). Of these patients, the diagnostic accuracy of the initial percutaneous renal mass biopsy was 76%, with an overall sensitivity and specificity of 75.4% and 100%, respectively. The biopsy concordance to final histologic tumor subtype was 93%. Larger tumor size (odds ratio [OR], 2.20; 95% confidence interval [CI], 0.55 to 8.88) and increasing number of biopsies (OR, 2.50; 95% CI, 0.59 to 10.69) were associated with increasing accuracy of a biopsy result to predict cancer; however, these associations were not statistically significant. CONCLUSION Percutaneous renal mass biopsy is diagnostically accurate and has good sensitivity, specificity, and concordance with final pathologic renal cell carcinoma subtype. This diagnostic modality can assist in management of select renal masses as treatment options are expanding.