Grading of bladder cancer: updates, controversies and practical solutions

Bladder cancer grading provides important prognostic information to clinicians, and the assigned grade is used as a variable in risk stratification models. There have been multiple proposed grading schemes over the last century, with the most widely utilized in contemporary practice being the World Health Organization (WHO) 1973 and 2004 schemes, with WHO 2004 used almost exclusively in North America, and dual grading using both 2004 and 1973 is in widespread use in Europe. Recently, there has been increased interest in hybrid grading schemes for papillary bladder cancer. These combine features from both aforementioned schemes and have demonstrated prognostic performance that exceeds WHO 2004 and WHO 1973. In this article, we review the historical background and new concepts in bladder cancer grading, highlight the opinions and perspectives of clinicians and pathologists, and assess the challenges along with evidence for and against different grading schemes. We discuss the potential contribution of hybrid 3-tier grading of bladder cancer and how this could impact the classification of papillary urothelial neoplasms and shape future grading scheme proposals.