A possible specific chromosome change in transitional cell carcinoma of the bladder.

Chromosome changes were ascertained in nine tumor samples from seven untreated patients with transitional cell carcinoma of the urinary bladder. All tumors analyzed showed abnormal karyotypes. In one tumor, a single numerical abnormality (+7) was the sole detectable change. From 1 to 19 structurally abnormal chromosomes could be identified in the remaining 8 tumors. The same abnormality, an isochromosome of the short arm of chromosome #5, was found in five tumors from four patients. We have previously described the presence of this marker chromosome in three of nine cases of transitional cell carcinoma of the bladder. We therefore conclude that i(5p) constitutes the most consistent nonrandom chromosome abnormality in this malignancy. Other chromosomes most frequently involved in structural changes in the present series of tumors were chromosomes #1, #6, #11, and #13.