Chromophobe renal cell carcinoma: the impact of tumor grade on outcome.

It has been reported that Fuhrman grading is not appropriate for chromophobe renal cell carcinoma (RCC). The objective of this study was to determine whether nucleolar grading and the recently described chromophobe RCC grading system by Paner and colleagues provide prognostic information. Pathologic features of 185 patients with chromophobe RCC treated surgically between 1970 and 2006 were reviewed, including nucleolar grade, chromophobe RCC grade, the 2010 TNM groupings, sarcomatoid differentiation, and coagulative tumor necrosis. Cancer-specific (CS) survival was estimated using the Kaplan-Meier method, and associations with CS survival were evaluated using Cox proportional hazard regression models. Twenty-three patients died from RCC at a mean of 3.0 years after surgery (median 1.3; range 0 to 16) with estimated CS rates (95% confidence interval) of 89% (84 to 94), 86% (81 to 92), and 85% (78 to 91) at 5, 10, and 15 years after surgery. Univariate associations with CS survival included the 2010 TNM stage groupings, sarcomatoid differentiation, coagulative tumor necrosis, chromophobe RCC grade, and nucleolar grade (all P<0.001). These last 4 features remained significantly associated with CS survival after adjusting for the 2010 TNM stage groupings. When the analysis was restricted to the 155 patients with nonsarcomatoid TNM stage groupings I and II chromophobe RCC, only stage grouping (I vs. II) was significantly associated with CS survival (P=0.03). Although the chromophobe RCC grading system described by Paner and colleagues and nucleolar grade are associated with CS survival in chromophobe RCC, they add no additional prognostic information once TNM stage and sarcomatoid differentiation are assessed.