Percutaneous biopsy of primary tumor in metastatic renal cell carcinoma to predict high risk pathological features: comparison with nephrectomy assessment.

PURPOSE As treatment options evolve for metastatic renal cell carcinoma, there is a need for predictive information to help guide therapy. We assessed the accuracy of percutaneous primary tumor biopsy for metastatic renal cell carcinoma by comparing biopsy findings to final nephrectomy pathology in patients undergoing cytoreductive nephrectomy. MATERIALS AND METHODS Using an institutional database we reviewed the records of patients who underwent percutaneous primary tumor biopsy before cytoreductive nephrectomy. In patients who underwent biopsy elsewhere pathology findings were re-reviewed at our institution. Differences in accuracy based on biopsy technique, imaging modality and biopsy period were determined by chi-square analysis. RESULTS We identified 166 patients who underwent percutaneous biopsy of the primary tumor before cytoreductive nephrectomy between 1991 and 2007, and had data available for review. Median pathological tumor size was 9.1 cm (range 3 to 32). Median time from biopsy to surgery was 46 days (range 6 to 717). Of 104 patients in whom biopsy was assigned a Fuhrman nuclear grade 33 (31.7%) had the same grade in the nephrectomy specimen, including 74 of 109 (67.9%) when considering only high or low grade. Grade change by more than 2 points was seen in 18 of 104 patients (17.3%). Sarcomatoid features were present in 34 of 166 nephrectomy specimens (20.5%) but only 4 (11.8%) were identified preoperatively. CONCLUSIONS In patients with metastatic renal cell carcinoma percutaneous renal biopsy has poor accuracy to assess Fuhrman nuclear grade or sarcomatoid features. Physicians should use caution when using biopsy data to guide therapy.