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Aims: The aims of this study were to evaluate the impact of tumour‐associated necrosis (TAN) on metastasis‐free survival for clear cell renal cell carcinoma (RCC), and to determine whether TAN provides survival information additional to World Health Organization (WHO)/International Society of Urological Pathology (ISUP) grading. Methods and results: The study consisted of 376 cases of clear cell RCC treated by nephrectomy, for which follow‐up was available. WHO/ISUP grade was assigned, and sections were assessed for the presence of TAN. American Joint Committee on Cancer (AJCC) pT staging category and tumour size were also recorded. The development of metastatic disease was taken as the clinical endpoint, and survival analyses, utilising univariate and multivariate models, were performed. WHO/ISUP grades were: grade 1, 35 cases (9.3%); grade 2, 188 cases (50.0%); grade 3, 91 cases (24.2%); and grade 4, 62 cases (16.5%). Staging categories were pT1–pT2 [234 tumours (62.2%)] and pT3–pT4 [139 tumours (37.0%)]. TAN was seen in 128 cases (34.0%). Neither TAN nor metastases were seen in grade 1 tumours. Among grade 2–4 tumours, those with TAN had a significantly worse prognosis than those without TAN (P = 0.017, P = 0.04, and P = 0.006, respectively). Multivariate analysis (WHO/ISUP grade, pT staging category, and TAN) showed all three variables to be independently associated with outcome (P = 0.009, P = 0.005, and P = 0.001, respectively). For all tumour grades and pT staging categories, it was found that the presence of TAN was associated with a 2.91‐fold greater risk of metastatic disease. Conclusion: Tumour‐associated necrosis is an important prognostic factor for clear cell RCC, independently of WHO/ISUP grade. This supports the suggestion that TAN could be incorporated into tumour grading criteria. [ABSTRACT FROM AUTHOR]

Grading of renal cell carcinoma (RCC) has been recognised as a prognostic factor for almost 100 years. Numerous grading systems have been proposed, initially focusing upon a constellation of cytological features and more recently on nuclear morphology. It has been recommended that grading of RCC should be based upon nucleolar prominence/eosinophilia for grades 1–3, while grade 4 requires nuclear anaplasia (including tumour giant cells, sarcomatoid differentiation and/or rhabdoid morphology). The grading system was adopted formally by the International Society of Urological Pathology (ISUP) and subsequently by the World Health Organisation (WHO), being designated the WHO/ISUP grading classification in the fourth edition of the WHO classification tumours of the urinary system and male genital organs (2016). This grading system has been validated for both clear cell and papillary RCC. Validation studies for chromophobe RCC failed to demonstrate a correlation between grade and outcome for both the superseded Fuhrman grading system and the WHO/ISUP grading classification, and it has been recommended that these tumours not be graded. The WHO/ISUP system has been incorporated into the structured reports of the International Cancer Collaboration on Cancer Reporting for both clear cell and papillary RCC. It is also noted that other types of RCC may be graded, but it must be emphasised in the report that this is for descriptive and diagnostic purposes, and not outcome prediction. More recent studies have shown the incorporation of the presence of tumour necrosis into RCC grading to improve outcome prediction, and this has been validated in several studies. [ABSTRACT FROM AUTHOR]