[Clonal origin of multiple foci of urinary bladder cancer]

To analyze the pattern of molecular damages in urinary bladder cancer (UBC), the authors studied allelic imbalance of chromosome loci 9p21 and 17p13 in 22 patients diagnosed as having multiple primary UBC (2 to 5 foci in each patient). The state of markers has no informative value in 3 (13.6%) cases; in 9 (47.4%) of 19 informative cases, deletion of the same allele was determined in at least one of the loci in question in all tumor nodules, which may point to the monoclonal origin of multiple tumors in these patients. Five (26.3%) of the 19 patients exhibited deletion of the same allele in different tumor nodules, which is suggestive of the active process of clonal evolution and the feasibility of tumor subcloning, which does not preclude the possibility of monoclonal origin. Five (26.3%) of the 19 patients had an imbalance of different alleles in varying nodules, which may show the oligoclonal origin of the tumor nodules concerned. The concordant and discordant patterns of molecular damages are encountered virtually with the same frequency in the tumors of multiple primary UBC, which supports the view that its synchronous tumors can develop both monoclonally through intraluminal dissemination of tumor cells and when there are cancerization fields that determine the occurrence of oligoclonal tumors.