Pathologic grading is an important prognostic correlate and is only applicable to clear cell renal cell carcinoma and papillary renal cell carcinoma. In the previous WHO classification versions, the most commonly used classification was the 1982 Fuhrman 4-grade classification, and in 1998, the WHO recommended to combine grades I and II of the Fuhrman classification into one grade, i.e., highly differentiated, grade III as moderately differentiated, and grade IV as poorly differentiated or undifferentiated. The WHO/ISUP pathology grading system (Table 3) has been further adjusted from the original Fuhrman four-grade grading system, and objective evaluation criteria have been added to form the WHO/ISUP pathology grading system, making it more operable and reproducible in practice.
Table 3 WHO/ISUP Nuclear Grading Criteria for Renal Cell Carcinoma, 2016 Edition