Introduction: The historical incidence of benign pathology after partial nephrectomy (PN) has ranged from 15-30%. In contemporary practice, advances in imaging modalities have improved the ability to differentiate benign renal masses such as lipid poor AMLs and benign complex renal cysts. We sought to examine the incidence of benign pathology in a contemporary cohort of patients undergoing PN for presumed RCC.
Methods: We reviewed the records of patients who underwent PN between January 1st 2006 and December 31st, 2019 for suspected RCC. Patients with cystic renal masses or definitive benign pathology on pre-operative imaging were excluded from analysis. Pre-operative characteristics for patients with benign and malignant pathologies were collated. Trends in the incidence and type of benign pathology were analyzed. Statistical analysis was performed using Student’s T test for continuous variables, Chi-Squared for categorical variables, and univariate linear regression for trendlines.
Results: 1083 patients were included in the analysis, with 210 patients (19.4%) identified to have benign disease on final pathology. Of the patients with benign disease, 49 patients (23%) had AML and 135 patients (64%) had oncocytoma. On univariate analysis, patients with benign pathology were more likely to be female (46% vs 28%, p<0.001), have a tumor size = 4 cm (85% vs 79%, p<0.05) and more likely to have multifocal disease (8% vs 5%, p<0.01). When reviewing PN pathology between 2006 to 2019, there was a significant increase in the incidence of benign pathology (R2=0.29, p<0.05). When examining 3-year averages over this same time period, the incidence of oncocytoma increased (51% to 59%) while the incidence of AML decreased (49% to 30%).
Conclusions: The incidence of benign pathology in this contemporary cohort of patients undergoing PN for presumed RCC did not decline over time. Despite improvements in imaging, benign renal masses, particularly oncocytoma, continue to pose a diagnostic challenge in patients with solid small renal masses.
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