What is the ISUP/WHO grading system for renal cell carcinoma (RCC)?

Updated: Jul 02, 2019
  • Author: YiFen Zhang, MD, PhD; Chief Editor: Liang Cheng, MD  more...
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In 2012, the International Society of Urologic Pathologists (ISUP) proposed a novel, validated grading system for clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) that has been implemented by the World Health Organization (WHO). [3, 4] This system is based primarily on the nucleoli assessment of the tumors, as follows [4] :

  • Grade 1: Inconspicuous nucleoli at ×400 magnification and basophilic
  • Grade 2: Clearly visible nucleoli at ×400 magnification and eosinophilic
  • Grade 3: Clearly visible nucleoli at ×100 magnification
  • Grade 4: Extreme pleomorphism or rhabdoid and/or sarcomatoid morphology

The ISUP/WHO grading system has been shown to provide superior prognostic information in cases of ccRCC compared with the Fuhrman grading system. [5]  A study of 681 cases of ccRCC found that 144 tumors (21.1%) could not be assigned a Fuhrman grade owing to ambiguous grading features. [5]

Studies suggest that adding the presence of tumor-associated necrosis into the ISUP/WHO grading system improves outcome predictions as it is an independent prognostic factor for ccRCC. [3, 6]

Although the ISUP/WHO grading system is not validated as a prognostic parameter for other tumor subtypes, it has utility for descriptive purposes. [3, 4] This grading system and the Fuhrman grading system are not recommended for grading chromophobe renal cell carcinomas (RCCs), [3, 4] as validation studies did not demonstrate a correlation between grade and outcome with both grading systems. [3]

See Renal Cell Carcinoma: Recognition and Follow-up, a Critical Images slideshow, to help evaluate renal masses and determine when and what type of follow-up is necessary.

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