Renal tumour size measured radiologically before surgery is an unreliable variable for predicting histopathological features: benign tumours are not necessarily small

OBJECTIVE To compare histopathological findings as a function of radiological tumour size, as published data suggest that small renal tumours are often benign and large tumours are renal cell cancer (RCC). PATIENTS AND METHODS Data from 543 surgically treated patients with solid renal tumours were analysed retrospectively. Tumour size measured by computed tomography (CT) before surgery was stratified into seven subgroups (cm): 0-2, 2.1-3, 3.1-4, 4.1-5, 5.1-6, 6.1-7 and > 7, and correlated with final histology. RESULTS In all, 80 lesions (14.7%) were benign on final histology; tumour size did not correlate with benign histology (P = 0.660). Histopathological tumour size was not statistically significant different (P = 0.521) from measured tumour size on CT, and there was no statistical significance between CT and histopathological tumour size (P = 0.528). Only 13 (17%) of lesions were correctly defined as benign on CT before surgery, whereas 67 (83%) were considered to be suspicious for malignant disease. Only one patient with a tumour correctly defined as benign had a radical nephrectomy; by contrast, 28 of 67 (42%) had a radical nephrectomy for benign lesions not correctly identified as benign on CT before surgery (P < 0.001). CONCLUSION Substantially many renal masses are benign, independent of tumour size. Radical nephrectomy could potentially have been avoided in 42% of patients with benign renal tumours. These data provide a good argument for the use of a more refined preoperative diagnostic evaluation, in particular needle biopsy.