Low incidence of benign lesions in resected suspicious renal masses greater than 2 cm: Single‐center experience from Japan

Objective: To assess the incidence of benign renal lesions in our Japanese clinical experience with surgical resection. Methods: A total of 411 renal masses harvested by radical or partial nephrectomy between January 1991 and April 2011 at our institution were retrospectively assessed. The incidence of benign lesions in 1‐cm increments in diameter was determined, and a logistic regression model was used to assess relationships between the incidence of benign lesions and other factors. Results: Histological examination confirmed a total of 18 (4.4%) benign lesions. The incidence of benign lesions was 42.8% for nodules <1 cm and 10.0% for nodules 1 to <2 cm. In contrast, the incidence of benign lesions in each 1‐cm increment between 2 and 6 cm was 4.1–4.9%. The incidence of benign lesions 2 to <4 cm was 4.8% and of benign nodules ≥6 cm was just 0–1.0%. The incidence of benign lesions ≥2 cm (3.5%) was significantly lower than that of masses <2 cm (16.2%; P < 0.001). Multivariate analysis showed that female gender (odds ratio 3.68) and smaller mass size (<2 cm; odds ratio 4.84) were significant predictors for benign lesions. Conclusions: The incidence of benign lesions among renal masses ≥2 cm in diameter was found to be much lower than previously reported. This should be taken into account when designing strategies for the management of suspicious small renal masses.