[Small incidental renal tumors. Evaluation and biological parameters].

Tumor size is a prognostic marker and correlates to survival after surgical therapy. Of 287 patients with small (<or=4 cm) renal tumors, 19.5% had a benign lesion and thus harmless. All others were renal cell cancers; 4.9% of tumors were detected because of metastases and consecutively treated. Tumors with a diameter <or=3 cm showed a tumor stage >or=pT3a in 10.9%, a high Fuhrman grade >or=3, multifocality in 8.5%, and metastases in 2.4%. Tumors with a diameter of 3.1-4 cm showed dramatically more aggressive parameters; 35.7% had stage >or=pT3a, 25.5% Fuhrman grade >or=G3, and 8.4% metastases (M+). However, evaluation of the tumor diameter on CT has an error of about +/-0.3 cm, which will lead to an even more pronounced error in volume determination. Therefore, determination of growth in follow-up imaging is unreliable. With the exception of the typical angiomyolipoma, determination of dignity for small solid kidney lesions is unreliable even with modern imaging. Only 17% of 80 benign lesions in our series were assessed as benign on preoperative CT. Thus, preoperative evaluation not only based on imaging seems to be valuable, especially in patients with higher surgical risk. Percutaneous renal mass biopsy has an accuracy of over 90% for detecting benign lesions and can influence therapeutic decisions, especially in patients with higher surgical risk.