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What you should know about grading in RCC: Fuhrman grade has been replaced by the new ISUP classification

Roberta Lucianò, Nazario Pio Tenace

The 4-tiered Fuhrman grading system for renal cell carcinoma (RCC) has been traditionally employed to assess aggressiveness of neoplastic cells. However, its scarce interobserver reproducibility, together with a questionable prognostic significance, has pushed the International Society of Urological Pathology (ISUP) to propose a new grading system (i.e. the ISUP grading), which has been implemented in the latest 2016 version of the WHO “blue book” on urogenital tumors. In this novel ISUP classification, which applies to clear cell and papillary RCC, grade 1–3 tumors are assessed based on nucleolar prominence, whereas grade 4 is defined by the presence of tumor cells with sarcomatoid and/or rhabdoid morphology and/or tumors containing tumor giant cells or showing extreme nuclear pleomorphism. As nucleolar grading has been shown superior to traditional Fuhrman grading as prognostic predictor, the current ISUP grading must be present in the pathologic report for clear cell and papillary RCC.

Figure 1 – Examples of different ISUP grades (Grade 1-4, a-d)