Pathologic features of renal masses, 4cm or less in diameter: The prevalence of benign tumors

Purpose: We examined the clinical and pathologic findings of small renal masses that were suspected to be malignant. We investigated the prevalence and the predictors of benign tumors. Materials and Methods: We retrospectively reviewed the medical records of the patients who underwent surgeries for renal lesions between September 1994 and June 2007. We analyzed the pathologic reports and medical records of 586 patients who had a renal mass that was 4cm or less. The mean patient age was 53 years (age range: 15-82). There were 418 male patients (71.3%) and 168 females (28.7%). Multiple logistic regression analysis was done to determine the clinical factors associated with benign renal masses, including the radiological tumor size, a cystic versus solid appearance, gender, age and the presenting symptoms. Results: Of the 586 renal masses, 62 (10.6%) were benign, 520 (88.7%) were renal cell carcinoma and 4 (0.7%) were other malignancies. The proportion of benign lesions was significantly higher in the females than that in the males (21.4% vs. 6.2%, respectively, p<0.001) and the proportion of benign lesions was significantly higher for the smaller masses (0-2cm) than for the 2.14cm sized tumors (14.7% vs. 9.1%, respectively, p=0.048). On multivariate analysis, gender and tumor size were significantly associated with malignant histology with the males having an odds ratio (OR) of 4.16 (95% CI 2.41-7.19, p<0.001) and the tumor size more than 2cm having an OR of 1.93 (95% CI 1.08-3.44, p=0.03). Conclusions: A considerable number (10.6%) of benign lesions 4cm or less in the radiological diameter were operated on based on suspicious preoperative imaging. The results of this study seem to help not only for counseling the patients, but also for deciding on a therapeutic modality preoperatively.