Multilocular Cystic Renal Cell Carcinoma: Pathological T Staging Makes No Difference to Favorable Outcomes and Should be Reclassified.

PURPOSE We evaluated survival outcomes of cystic/multilocular cystic renal cell carcinomas in a long-term population based study based on size and pathological tumor stage. MATERIALS AND METHODS We retrospectively reviewed a provincial cancer registry of all histologically proven cases of multilocular cystic renal cancers treated surgically between 1995 and 2008. All cases of cystic necrosis were excluded from study. Primary end points were overall and cancer specific survival estimated using Kaplan-Meier curves. Cox proportional hazards models of univariable and multivariable analyses were used to assess for factors associated with survival. RESULTS Of 172 cases of cystic renal cancers 168 with complete data were analyzed, of which 98% were multilocular cystic. Median patient age at treatment was 55 years and 58% of the patients were male. More than 40% of cases were pT1b or greater, 15% were pT2 or greater and most cases were low Fuhrman grade (1-2). At a median followup of 9.75 years overall and cancer specific survival was 82.1% and 100%, respectively. No difference was noted in higher pathological T stage, size or grade. Limitations inherent in population based studies include under ascertainment of cause of death, lack of data on histologically benign cysts that are treated surgically and a lack of central pathology review. CONCLUSIONS Multilocular cystic renal cell carcinoma has an excellent prognosis, which remains unchanged regardless of tumor size or pathological T stage. This suggests a strong case for nephron and adrenal sparing surgery when indicated, and nonsurgical management when feasible. Since postoperative followup protocols are dictated by staging, we propose that for this entity pathological T staging should be abandoned or reassigned as pT1c to guide clinicians.