Incidental renal tumours: the frequency of benign lesions and the role of preoperative core biopsy

OBJECTIVE: To determine the incidence of benign renal lesions in incidentally discovered small renal tumours, increasingly detected by the widespread use of abdominal imaging, and to evaluate whether preoperative renal core biopsy is effective in identifying benign lesions. MATERIALS AND METHODS: In a retrospective study, renal core biopsies for incidental tumours over a 5-year period were analysed. The biopsies were correlated with the final pathology of the nephrectomy specimens, or with patient follow-up if nephrectomy was avoided. RESULTS: Of 70 diagnostic core biopsies, a third of cases were considered benign. The sensitivity and specificity for both benign and malignant lesions when compared to definitive pathology was 100% in all cases subjected to nephrectomy. Of the 30 non-diagnostic biopsies, three were proved to be benign, and 18 likely to be benign. The only complication of renal biopsy was one case of bleeding after biopsy. CONCLUSION: A higher than previously anticipated proportion of incidentally detected small renal masses are benign. Given the high sensitivity and specificity, there is value in taking a core biopsy of small incidental renal lesions, a procedure with a low complication rate (1%). When analysed by a pathologist familiar with renal biopsy, this might avoid radical nephrectomy in many patients.