Tailoring Renal Mass Biopsy: Optimal Core Number and Location Based on Tumor Size for Enhanced Diagnostic Accuracy- A Prospective Ex-Vivo Study.

Objective: To determine the optimal number and location of biopsy cores in renal masses based on mass size in order to maximize diagnostic accuracy.

Methods: This observational study included 360 patients with renal masses, who were divided equally into six groups. Each group was matched in terms of mass size (mass size category: ≤ 4 cm (T1a), 4-7 cm (T1b), 7-10 cm (T2a), and > 10 cm (T2b)). Core needle biopsies were taken after resection of the mass in an ex-vivo setting. The masses in the first, second, third, and fourth groups underwent 1, 2, 3, and 4 peripheral biopsies, respectively. The masses in the fifth and sixth groups were subjected to 1 and 2 central biopsies, respectively. The results of the biopsies were compared with permanent histopathology results, and the impact of mass size, number of biopsy cores, and location of biopsies on the accuracy of biopsy results were analyzed.

Results: In T1a and T1b size categories, the most accurate diagnostic results were obtained with three peripheral or two central biopsies. However, in T2a and T2b size categories, the most accurate diagnostic results were obtained with four peripheral or two central biopsies. Histological characteristics of the masses did not have statistically significant effect on the diagnostic accuracy of the biopsies.

Conclusion: Our findings demonstrate that for masses ≤ 7 cm, three peripheral or two central samples provide the highest diagnostic accuracy. For masses larger than 7 cm, four peripheral or two central biopsy cores offer the best diagnostic accuracy.