Outcomes of small renal mass needle core biopsy, nondiagnostic percutaneous biopsy, and the role of repeat biopsy

Background: Percutaneous needle core biopsy has become established in the management of small renal masses ≤ 4 cm (SRMs). Recent series have reported success rates of ≥ 80%. Nondiagnostic results continue to be problematic.

Objective: To determine the results of SRM biopsy and the outcomes of nondiagnostic biopsy and repeat biopsy.

Design, setting, and participants: Patients undergoing renal tumor biopsy (RTB) for suspected renal cell carcinoma (RCC) were included in a prospectively maintained database.

Measurements: The database was analyzed retrospectively to determine the pathology and outcomes of SRM biopsy. Outcomes of patients with nondiagnostic biopsy were determined. Patients undergoing repeat biopsy were identified and their outcomes analyzed.

Results and limitations: Three hundred forty-five biopsies were performed (mean diameter: 2.5 cm). Biopsy was diagnostic in 278 cases (80.6%) and nondiagnostic in 67 cases (19.4%). Among diagnostic biopsies, 221 (79.4%) were malignant, 94.1% of which were RCC. Histologic subtyping and grading of RCC was possible in 88.0% and 63.5% of cases, respectively. Repeat biopsy was performed in 12 of the 67 nondiagnostic cases, and a diagnosis was possible in 10 (83.3%). Eight lesions were malignant and two were oncocytic neoplasms. Pathology was available for 15 masses after initial nondiagnostic biopsy; 11 (73%) were malignant. Larger tumor size and a solid nature on imaging predicted a successful biopsy on multivariate analysis. Grade 1 complications were experienced in 10.1% of cases, with no major bleeding and no seeding of the biopsy tract. There was one grade 3a complication (0.3%). This is a retrospective study and some data are unavailable on factors that may affect biopsy success rates. Repeat biopsy was not standard practice prior to this analysis.

Conclusions: RTB can be performed safely and accurately in the investigation of renal masses ≤ 4 cm. A nondiagnostic biopsy should not be considered a surrogate for the absence of malignancy. Repeat biopsy can be performed with similar accuracy, providing a diagnosis for most patients.