Prevalence and predictors of benign lesions in renal masses smaller than 7 cm presumed to be renal cell carcinoma

Purpose: To determine the association between preoperative parameters with final benign pathology in patients who underwent surgical removal of solitary renal masses <7 cm in diameter. Materials and Methods: A database of 450 patients without metastatic disease who underwent radical nephrectomy or nephron-sparing surgery (NSS) for removal of renal masses <7 cm between January 1990 and December 2009 was reviewed. Age, sex, symptoms, year and type of surgery, solid or cystic appearance, and tumor size were analyzed as presumed predictors of benign pathology. Multivariate analysis was performed to identify parameters associated with benign pathology. Results: In all, 88 (19.9%) of the tumors were benign, including 39 (8.7%) oncocytomas and 22 (4.9%) angiomyolipomas. The benign lesion rate for tumors ≤2, 2.1-4, and 4.1-7 cm was 30.3%, 27.1%, and 12.5%, respectively (2P <.001). For the periods of 1990-1996, 1997-2003, and 2004-2009, the frequency of benign tumors was 25%, 17.3%, and 18.4% (2P =.271), the incidental tumor rate was 48.1%, 60.4%, and 63.8% (2P =.027), mean tumor size was 5, 4.6, and 4.1 cm (2P <.001), and the NSS rate was 28.8%, 43.2%, and 52.7% (2P <.001), respectively. Logistic regression analysis revealed that female sex, NSS, surgery between 1990 and 1996, cystic components on imaging, and small tumors (<4 cm) based on radiologic examination were independently associated with benign pathology (odds ratio [OR] = 3.26, 2.56, 2.43, 2.41, and 1.96, respectively). Conclusions: The incidence of incidental and small tumors amenable to NSS increased over time. Female sex was the strongest predictor of benign pathology.