Clear cell renal cell carcinoma: Validation of WHO/ISUP grading

In 2012, the International Society of Urological Pathology (ISUP) introduced a novel grading system for clear cell and papillary renal cell carcinoma (RCC) based upon increasing nucleolar prominence in grades 1 to 3, with the presence of extreme nuclear pleomorphism and/or tumour giant cells and/or sarcomatoid and/or rhabdoid differentiation as criteria for grade 4. This system is now incorporated in the latest World Health Organization renal tumour classification, being designated WHO/ISUP grading.

This study was undertaken to compare WHO/ISUP and Fuhrman grading and to validate WHO/ISUP grading as a prognostic parameter in a series of clear cell RCC. Analysis of 681 cases of clear cell RCC showed that 144 tumours could not be assigned a Fuhrman grade on the basis of ambiguous grading features.

The application of WHO/ISUP grading resulted in a general down-grading of cases when compared with Fuhrman grading. In a sub-group of 376 cases, for which outcome data were available, 9.3% were WHO/ISUP grade 1, 50.0% were grade 2, 24.2% grade 3 and 16.5% grade 4, while the distribution of Fuhrman grades was 0.4% grade 1, 48.7% grade 2, 29.4% grade 3 and 21.5% grade 4. There were no recurrence/metastases amongst patients with WHO/ISUP grade 1 tumours and there was a significant difference in outcome for WHO/ISUP grades 2, 3 and 4. For Fuhrman grading the cancer-free survival was not significantly different for grade 2 and grade 3 tumours. On multivariate analysis WHO/ISUP grade and pT staging category were found to retain prognostic significance. This article is protected by copyright. All rights reserved.

Histopathology. 2017 Jul 18 [Epub ahead of print]

Julien Dagher, Brett Delahunt, Nathalie Rioux-Leclercq, Lars Egevad, John R Srigley, Geoffrey Coughlin, Nigel Dunglinson, Troy Gianduzzo, Boon Kua, Greg Malone, Ben Martin, John Preston, Morgan Pokorny, Simon Wood, John Yaxley, Hemamali Samaratunga

Aquesta Specialized Uropathology, Brisbane, QLD, Australia., Rennes University Hospital, Rennes, France., Department of Oncology-Pathology, Karolinska Institute, Stockholm, Sweden., Wesley Hospital, Brisbane, Qld, Australia., Greenslopes Hospital, Brisbane, Qld, Australia., Holy Spirit Northside Hospital, Brisbane, Qld, Australia.