There are several classifications of tumours of the urinary bladder still being used: the WHO classification of 1973, the WHO classification of 1999, the “Scandinavian” system, the “American” system. These classifications use different names and different criteria, which cause important problems in communication. The WHO classifications published in 1999, was supposed to clarify these problems, but it was not widely accepted both by clinicians and pathologists. Especially urologists did not accept such a wide scale of tumours, with a new entity: PUNLMP (papillary urothelial neoplasm of low malignant potential). From the clinical point of view, the most important information is the clinical stage and histological grade but only on a dual scale: high grade (G2/3) or low grade (PUNLMP, papilloma, carcinoma G1). These differences between histological classifications and clinicians need to be clarified.

Molecular studies provide important information for histological and clinical classifications of the bladder tumors. Mutations of FGFR3 (fibroblast growth factor receptor 3 gene) often occur in low grade and early stage tumours, whereas they are very rare in high grade or advanced cancers. Moreover, FGFR3 mutation seems to be a better prognostic factor than histological grade and stage. Thus, FGFR3 mutations may be regarded as a “marker” of benign tumours, and as recently reported alternative genetic pathway for P53 mutations, which occur in more malignant tumours. From these studies, it seems possible that a majority of high grade, advanced tumours growth “de novo”, not on the basis of previous low grade tumour.