Purpose: Percutaneous biopsy of small renal tumors has not been historically performed because of concern about complications and accuracy. We reviewed our experience with percutaneous needle biopsy of small renal masses to assess the safety and accuracy of the procedure, the potential predictors of a diagnostic result and the role of biopsy in clinical decision making.
Materials and methods: A total of 100 percutaneous needle biopsies of renal masses less than 4 cm were performed between January 2000 and May 2007 with 18 gauge needles and a coaxial technique under ultrasound and/or computerized tomography guidance. A retrospective chart review was performed to document the complication rate and the ability to obtain sufficient tissue for diagnosis. Tumor size, tumor type (solid vs cystic), image guidance, biopsy number and core length were assessed for the ability to predict a diagnostic biopsy.
Results: No tumor seeding or significant bleeding was observed. Of the core biopsies 84 (84%) were diagnostic for a malignant (66) or a benign (18) tumor. Larger tumor size and a solid pattern were significant predictors of a diagnostic result. Histological subtyping and grading were possible on core biopsies in 93% and 68% of renal cell carcinomas, respectively. A total of 20 patients underwent surgery after a diagnostic biopsy. The histological concordance of biopsies and surgical specimens was 100%.
Conclusions: Percutaneous needle biopsy of renal masses less than 4 cm is safe and provides adequate tissue for diagnosis in most cases. Larger tumor size and a solid pattern are significant predictors of a successful biopsy. Renal tumor biopsy decreases the rate of unnecessary surgery for benign tumors and can assist the clinician with treatment decision making, especially in elderly and unfit patients.