Fuhrman grade provides higher prognostic accuracy than nucleolar grade for papillary renal cell carcinoma

Recent evidence suggests that nucleolar grade but not Fuhrman grade is applicable to papillary renal cell carcinoma. We tested this hypothesis in an independent large series from a single institution.

One dedicated uropathologist regraded 158 cases of papillary renal cell carcinoma by nucleolar and Fuhrman grades. The prognostic value and predictive accuracy of these grading systems to predict disease specific survival were analyzed by Cox proportional hazards models and the concordance index.

There were 39 papillary renal cell carcinoma related deaths (25%) at a mean followup of 50 months. On univariate analysis nucleolar grade predicted disease specific survival with a concordance index of 67.8% but the survival difference between grades 1 and 2 did not attain statistical significance (p = 0.1441). Fuhrman grade predicted disease specific survival significantly better (concordance index 74.7%, p <0.001). Comparison of survival estimates between the grades revealed statistical significance across each grade category (each p <0.05). Fuhrman but not nucleolar grade was retained as an independent prognostic factor on multivariate analysis (p = 0.027 and 0.128, respectively).

Each grading system performs well but the predictive accuracy of Fuhrman grade is statistically superior to that of nucleolar grade and only Fuhrman grade provides independent prognostic information on patients with papillary renal cell carcinoma. Thus, Fuhrman grade should be the standard grading system for papillary renal cell carcinoma.