Partial Nephrectomy for Presumed Renal-Cell Carcinoma: Incidence, Predictors, and Perioperative Outcomes of Benign Lesions

Background: The aim of this study was to investigate the incidence of benign histology after partial nephrectomy (PN) in patients with presumed malignancy from preoperative imaging. Furthermore, preoperative predictors of benign lesions and perioperative outcomes were also assessed. Methods: A series of patients undergoing PN for renal masses was identified using a prospectively maintained database. Patients were excluded for known genetic conditions, if more than one renal mass was resected, or if standard preoperative imaging was not suspicious for renal-cell carcinoma (RCC). Differences in characteristics between patients with benign and malignant pathology were assessed. Results: A total of 916 patients were identified who underwent PN between 2007 and 2015, including 129 (14.1%) patients with a final diagnosis of benign disease. The most common types of benign pathology were oncocytoma (n = 66, 51.2%), angiomyolipoma (n = 37, 28.7%), and complex cysts (n = 10, 7.8%). Low body mass index (BMI) [0.96 (0.92-0.99) p = 0.02], low R.E.N.A.L. score [0.86 (0.76-0.96) p = 0.007], and low preoperative creatinine [0.37 (0.14-0.91) p = 0.04] predicted benign histology in multivariate analysis. Tumor size was a significant predictor in additional modeling [0.81 (0.69-0.94) p = 0.008]. Patients with benign histology had significantly shorter operative times (p < 0.001) and less estimated blood loss (p < 0.001), and there was no difference in complication (p = 0.93) or blood transfusion (0.24) rates. Conclusions: In this study, the rate of benign pathology after PN for presumed RCC is 14.1%. BMI, R.E.N.A.L. score, and preoperative creatinine are predictive of benign histology, but the ability of different variables to predict benign lesions may be influenced by the distribution of benign tumor subtypes, reflecting potential unidentified selection bias.