Résumé
Purpose: We determined the accuracy of renal biopsy in predicting histological subtype and final Fuhrman nuclear grade in small (4 cm or smaller) renal cancers, and evaluated the concordance between renal biopsy and surgery for these 2 criteria.
Materials and Methods: A total of 187 percutaneous needle biopsies of small renal tumors, guided by computerized tomography with gauge needles and a coaxial technique, were consecutively performed between 2006 and 2011. Renal cell carcinoma was diagnosed in 132 tumors. Partial or radical nephrectomy was performed for 61 of these carcinomas. Preoperative biopsy results for the operative specimens were compared with respect to histological subtype and Fuhrman nuclear grade. In addition, Kappa values were calculated as a measure of agreement between biopsy and surgical specimens, with correction for chance agreement to evaluate the concordance between biopsy and surgical classification for these criteria.
Results: Biopsy accuracy and the concordance between biopsy and surgery were excellent for determining histological subtype. The biopsy correctly identified the grade in 75% of cases, and in 93% when pooling renal cell carcinoma in low (1 or 2) and high (3 or 4) grade cases. The agreement between biopsy and surgery for Fuhrman nuclear grade was moderate (Kappa = 0.52) and substantial (Kappa = 0.71) when pooling low and high grade carcinoma, respectively.
Conclusions: Although the concordance between grading on biopsy and with surgical specimens was moderate, likely because of the reproducibility of the grading system, the accuracy of biopsy for differentiating high and low grade small renal tumors was high, which may greatly impact decision making in cases of small renal cancer.