Interphase cytogenetics of a male breast cancer

Direct interphase cytogenetic analysis was performed on nuclei from a male breast tumor using fluorescence in situ hybridization (FISH). DNA probes specific for repetitive pericentromeric regions on chromosomes 1, 7, 9, 11, 15, 17, 18, X, and Y were used to determine chromosome copy numbers in interphase tumor cells. Copy number distributions varied greatly between chromosomes, showing major tumor populations with on (Y), two (X,9), three (11, 15, 18), and four (1, 7, 17) copies of the pericentromeric targets. The X chromosome was present in two copies in 84.7% of tumor nuclei, with the balance being primarily monosomic. Normal skin fibroblasts cultured from the same patient showed 99% monosomy X. The Y chromosome showed a minor population (12%) with two copies. The DNA index of the tumor was 2.0 as determined by flow cytometry. The proliferative activity of the tumor cells was simultaneously analyzed using detection of in vivo bromodeoxyuridine (BrdU) incorporation. The BrdU labeling index was 13.2%.