Comparison of accuracy of 14-, 18- and 20-G needles in ex-vivo renal mass biopsy: a prospective, blinded study.

Objective: To prospectively determine the accuracy of 14-, 18- and 20-G core needle biopsies to render the appropriate histological diagnosis of solid, enhancing renal masses, using a controlled, ex-vivo biopsy technique.
Patients and Methods: From March 2007 to September 2007, 31 patients undergoing partial or radical nephrectomy were randomly selected for biopsy. After extirpative surgery, three ex-vivo biopsies were taken from each lesion with 14-, 18- and 20-G biopsy needles. One experienced genitourinary pathologist, unaware of patient identifiers and final pathology results, determined the biopsy histology and tumour grade, based on standard haematoxylin and eosin (H&E) techniques and immunohistochemistry.
Results: The final pathological evaluation classified 21 masses (68%) as clear cell renal cell carcinoma (RCC), three (10%) as papillary RCC, three (10%) as chromophobe RCC, three (10%) as oncocytoma and one (3%) as a benign lymphoid infiltrate. The biopsy histology correlated with the final pathology in 29/31 cases (94%) with the 14-G, 30/31 cases (97%) with the 18-G and 25/31 cases (81%) with the 20-G needles. In two cases chromophobe RCC was misdiagnosed with oncocytoma, and vice versa.
Conclusion: In this study a minimum of an 18-G biopsy needle was the most accurate in determining the histological diagnosis. Clear cell and papillary RCCs were accurately diagnosed on biopsy using an 18-G, whereas oncocytoma and chromophobe RCC were difficult to differentiate using standard H&E techniques and immunohistochemistry.