Computed tomography-guided biopsy for small renal masses before or immediately after tumor ablation: factors affecting diagnostic yield.

Purpose: To evaluate the diagnostic yield of percutaneous renal mass biopsy (RMB) before and after ablation.

Materials And Methods: In total, 333 renal masses in 332 consecutive patients underwent computed tomography (CT)-guided biopsies and were included in this study. All biopsies were performed with 18-gauge core needles with CT fluoroscopic guidance before ablation (n  =  234) or immediately after radiofrequency ablation (RFA) (n  =  40) or cryoablation (CA) (n  =  59). The safety and diagnostic yield of RMB were evaluated. Both univariate and multivariate analyses were used to identify factors affecting diagnostic yield.

Results: No major complication occurred. The 281 specimens (84%) were diagnostic. There were 257 renal cell carcinomas (77%), 21 benign masses (6%), and 3 metastases (1%). The remaining 52 specimens (16%) were nondiagnostic. The diagnostic yields before ablation, after RFA, and CA were 91% (212/234), 80% (32/40), and 63% (37/59), respectively. Small masses (P  =  0.050 and 0.006), cystic masses (P < 0.001 and < 0.001), and post-CA (P < 0.001 and < 0.001) were independent and significant factors affecting the nondiagnostic results in both univariate and multivariate analyses.

Conclusion: CT-guided RMB can be nondiagnostic when the tumor is small, cystic, or biopsied immediately after CA.