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.