Incidence of benign lesions for clinically localized renal masses smaller than 7 cm in radiological diameter: influence of sex.

PURPOSE: We determined the incidence of benign renal lesions in patients undergoing definitive surgery for localized renal masses 7 cm or less in maximum radiological diameter, and assessed preoperative and clinical parameters associated with benign histology.
MATERIALS AND METHODS: The records of 1,184 patients who underwent consecutive partial or radical nephrectomies between January 2000 and January 2005 were retrospectively reviewed. We excluded 208 patients with lesions more than 7 cm in maximum radiological diameter, 17 with evidence of renal vein or vena caval invasion, 75 with suspected or documented metastatic disease, 28 with a history of renal cell carcinoma and 41 with no available imaging. Logistic regression was done to determine clinical factors associated with benign renal masses, including radiological tumor size, cystic vs solid appearance, patient sex, age, presenting symptoms and race.
RESULTS: Of 815 nephrectomies in our data set 134 (16.4%) were associated with benign lesions, including oncocytoma in 87 (10.7%), angiomyolipoma in 17 (2%), simple cysts in 10 (1.2%), metanephric adenoma in 8 (1%), cystic nephroma in 5 (0.6%) and other in 7. On multivariate logistic regression analysis only sex was significantly associated with benign histology with females having an OR of 1.8 (95% CI 1.2 to 2.6, p = 0.002). Tumor size was not independently associated with benign histology (p = 0.13).
CONCLUSIONS: A significant number (16.4%) of benign lesions less than 7 cm in radiological diameter were operated on based on suspicious preoperative imaging. Women had almost twice the likelihood of having a benign lesion.