A novel orthotopic bladder tumor model with predictable localization of a solitary tumor.

An ideal bladder tumor model consists in an orthotopic solitary tumor with a well-defined localization and stage, as well as unaltered normal mucosa. None of the existing models covers all these requirements. We have created a new model, suitable for diagnostic and therapeutic purposes. Female Fisher rats were divided into different groups according to bladder preconditioning and tumor cell (AY27) administration. Generalized desepithelialization was obtained by an intravesical instillation of HCl, neutralized by NaOH. Localized desepithelialization of the bladder fundus was the result of application of a micro-swab, imbibed with the same chemicals. Tumor cells administration was either generalized (intravesical instillation) or focal (micro swab). No bladder perforations were observed. Generalized desquamation always produced multifocal tumors, whereas focal application of HCl/NaOH resulted in solitary tumors of the bladder fundus, irrespective of the method of tumor cell administration. Only hyperplasia could be detected at day 3. AY27 cells were covered by umbrella cells at day 5 and subepithelial AY 27 tumor nests, covered by full thickness epithelium were observed day 7.