Chromosome instability and progression in urothelial cell carcinoma of the bladder.

Superficial urothelial cell carcinoma (UCC) is a heterogeneous group of neoplasia with an unpredictable clinical course. Numerical alterations of chromosomes 7, 9 and 17 in superficial and invasive UCCs were analysed to evaluate the importance of chromosome instability in the progression of these tumours. Our sample consisted of 75 patients (47 with superficial and 28 with invasive bladder tumours). In situ hybridization using centromeric probes for chromosomes 7, 9 and 17 was done for the chromosome analysis in paraffin-embedded tissues. From the results obtained it can be concluded that losses of genetic material seem to be important early events in the carcinogenesis of the urothelium, but during progression of UCCs there seems to be a selection of those cells with gains of genetic material. This chromosome instability may be due to the acquisition of mechanisms involved in aneuploidization, namely p53 function disorders.