HETEROGENEITY IN BLADDER-CANCER AS DETECTED BY CONVENTIONAL CHROMOSOME ANALYSIS AND INTERPHASE CYTOGENETICS

Thirty transitional cell carcinomas (TCCs) of the bladder were examine d by classical chromosome counting to establish range, modal number, a nd percentage of metaphases with 2n, 3n, 4n, and greater-than-or-equal -to 5n chromosomes. In addition, fluorescence in situ hybridization (F ISH) was applied to interphase nuclei to detect the percentage of tumo r cells showing polyploidization and chromosome imbalance. In FISH, ce ntromere-specific DNA probes for chromosomes 1, 7, 9, and 11 were used . The tumors were analyzed flow cytometrically to determine the DNA in dex (DI). Fourteen of 21 cases (67%) having a DI = 1 showed, after cla ssical chromosome counting, in addition to a diploid model number, som e cells with a 3n and 4n chromosome count. With FISH, eight cases (38% ) showed a low percentage of cells with multiple signals for each of t he probes, thus indicating polyploidization. In 13 (62%) cases, an imb alance between different chromosomes was detected. In nine tumors havi ng a DI of 1.6 to 1.9, classical chromosome counting showed low percen tages of greater-than-or-equal-to 5n cells in four cases, in addition to a triploid modal number. With FISH in six cases, a low percentage o f cells showed five or more signals for each of the chromosomes, indic ating polyploidization. In all cases, a chromosome imbalance was detec ted. With classical chromosome counting not all tumors can be analyzed . With FISH, small percentages of polyploid cells are not recognized. Both methods complement each other in that chromosome counting allows readier detection of heterogeneity in DNA-diploid tumors after polyplo idization, whereas FISH allows efficient recognition of the chromosome s involved in the process of imbalance.