Context: Tumour grade is an important prognostic indicator in non-muscle-invasive bladder cancer (NMIBC). Histopathological classifications are limited by interobserver variability (reproducibility), which may have prognostic implications.
European Association of Urology NMIBC guidelines suggest concurrent use of both 1973 and 2004/2016 World Health Organization (WHO) classifications. Objective: To compare the prognostic performance and reproducibility of the 1973 and 2004/2016 WHO grading systems for NMIBC.