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.