Clinical Implications of the 2004 WHO Histological Classification on Non-Invasive Tumours of the Urinary Bladder

The 1973 World Health Organization (WHO) typing system for bladder tumours is still widely used despite the lack of detailed histhopathological criteria. The more recent 2004 WHO “blue book” on pathology and genetics of tumours of the urinary system and male genital aimed to improve the recognition of subgroups by setting out well defined histomorphological criteria and dividing tumours with different biological characteristics that correlate with different clinical outcomes. However, the prognostic value of the 2004 WHO classification on non-invasive urothelial lesions is under discussion and there are questions concerning the clinical relevance of this system. This review is derived from data of available clinical trials to test the validity of the 2004 WHO classification for non-invasive bladder lesions by comparing tumour recurrence, progression and survival rates between different entities. Furthermore, we tried to evaluate the prognostic use of genetic alterations and biological markers with regard to impact on clinical management decisions.In our view, the 2004 WHO classification system does identify clinically and biologically distinct groups within the spectrum of non-invasive urothelial tumours. However, until the new classification is fully validated, and those working in the field have become familiar with it, the 1973 WHO typing system for bladder tumours is best mentioned additionally in the histopathological report.