A CRITICAL APPRAISAL OF THE CLASSIFICATION OF UROTHELIAL TUMOURS: TIME FOR A CHANGE, BUT NOT THE CHANGE PROPOSED

A recent proposal that noninvasive bladder tumours should not be considered as ‘cancer’ has challenged urological pathology dogma [1]. This bold proposal is based on the fact that, despite publication of the 1998 WHO/ International Society of Urological Pathology (ISUP) consensus classification for the grading of noninvasive bladder neoplasms, pathological categorization of these lesions remains elusive [2]. Nine years after adoption, these most recent recommendations have not achieved widespread acceptance, and many pathologists continue to report the 1973 nomenclature of non-muscle-invasive papillary lesions as papilloma, grade 1, 2 and 3, rather than the 1998 ‘Consensus’ recommendations of papilloma, papillary urothelial neoplasm of low malignant potential (PUNLMP), and lowand high-grade papillary urothelial carcinoma (PUC). A comparison between the 1973 and 1998 WHO classification schemes [3], that examined the risk of progression as defined by lamina propria or muscularis propria invasion or the subsequent development of UC in situ (flat CIS), has identified utility in the new classification scheme. In particular, the 1998 classification scheme more specifically identifies the morphological criteria that define those patients with high-grade PUC and therefore with a greater risk of progression. Furthermore, the stratification of a subset of noninvasive PUCs into lowand high-grade groups based on strict morphological criteria has yielded important insights into the molecular pathogenesis of these lesions, including the involvement of the KRAS/FGFR3 pathway in low-grade lesions and the p53/RB pathway in highgrade lesions.