Background: Facing the increasing frequency of urothelial neoplasms and stratified therapeutic strategy pathologists have to meet the demands of urologists for constantly increasing preciseness of the histopathology reports influencing the application of tailored therapeutic schemes. The WHO/ISUP consensus conference in 1998 (5) resulted into adoption of a new classification of the urothelial lesions (11). Its employment requires considering of features that can be difficult to find in the material provided. Material and methods: parallel typing of more than 200 urothelial neoplasms from the daily routine biopsy samples provided by the faculty of medicine urology clinic according to the previous Mostofi 1973 and the new WHO/ISUP 1998 classification. Results: Realizing the consultation demands we have identified some repetitive problems in the urothelium lesions diagnostics considering typing, grading, and staging of the lesions. Typing was a less frequent source of problems. It appeared in classifying lesions with inverted growth, and mucin producing urothelial neoplasms vs. adenocarcinomas. Less important typing problems are represented by uncommon rare diagnoses, as they manifest from the beginning as a specialty solvable mostly with the help of immunohistochemistry. Grading was experienced as troublesome in the following items: papillary hyperplasia vs. LG papillary ca, PUNLMP vs. LG papillary ca, HG papillary ca with a majority of LG material, monotonous types of HG flat lesions, and combined lesions. Staging difficulties applied mostly in identification of the initial unequivocal invasion and the substaging of pT1 into pT1a and pT1b with learning to find the decisive mucosa structures described in detail as late as 1983 (2). We have implemented reporting the presence/absence of the detrusor muscle in the material as a marker describing the representativness of the sample provided; we consider this approach less confusing than introduction of clinical staging terminology Ta, T1 instead of pTa, pT1. To help the practising pathologists accustomed to the previous classification system we have organized postgraduate courses dealing with the application of the new diagnostic criteria adopted by the new version WHO 2004 urothelial neoplasms classification. A slide collection from the routine biopsy material comparing the previous and the new classification and a reference image database with commented reference images are being developed in the LUCIA Net image archiving system. Free access for study is available at http://www.laboratory-imaging.com. Recently, it includes over 80 images. Conclusion: adopting the new system of urothelial lesions classification requires consideration of formerly not employed features. The learning can be simplified with both classical slide collection & e-learning image database.

        Key words: urothelial pathology – urothelial carcinoma – WHO/ISUP consensus of urothelial lesions classification