Pathological Concordance and Surgical Outcomes of Sporadic Synchronous Unilateral Multifocal Renal Masses Treated with Partial Nephrectomy

Purpose: Patients with unilateral synchronous multifocal renal masses represent a unique population with renal cell carcinoma. While pathological concordance rates have been studied for bilateral cases, limited data exist on unilateral multifocal disease. We characterized pathological concordance rates in this population and evaluated the outcomes of nephron preservation. Materials and Methods: Patients who underwent surgery from 2000 to 2012 for unilateral synchronous multifocal renal masses were identified from a prospectively maintained database. Demographic, surgical and pathological outcomes of this cohort were analyzed. Malignant concordance rates were defined as agreement of all malignant tumor types in a single renal unit. Histological concordance was defined as agreement of all resected mass histologies, eg all clear cell carcinomas. Nuclear grade was considered concordant if all tumors excised were low (Fuhrman 1 or 2, type 1) or high (Fuhrman 3 or 4, type 2) grade. Results: Using our institutional database of 2,569 patients with renal tumors we identified 97 with unilateral synchronous multifocal renal masses. Malignant and benign concordance rates were 77.2% and 48.6%, and histological and grade concordance rates were 58.8% and 51.5%, respectively. In this cohort we identified 76 patients (76.3% male) with a median age of 62.5 years who had a total of 241 unilateral synchronous multifocal renal masses and underwent nephron sparing surgery. Median mass size was 2.0 cm (IQR 1.1-3.1), there was a median of 3 tumors per patient and median followup was 24 months (IQR 13-40). Identified renal cell carcinoma histologies included clear cell in 49.4% of cases, papillary in 33.5%, mixed in 4.5% and chromophobe in 2.8%. Conclusions: In what is to our knowledge the largest published report of unilateral synchronous multifocal renal masses we document low pathological concordance rates. As such, percutaneous biopsy of a single renal mass in these patients may not help inform treatment decisions. Nephron sparing surgery may be performed with acceptable oncological and functional results in patients with unilateral synchronous multifocal renal masses.