Aneusomy and tumor heterogeneity in metastatic breast cancer detected by fluorescence in situ hybridization

Direct interphase cytogenetic analysis was performed on nuclei of metastatic effusions from breast cancer using fluorescence ill situ hybridization (FISH). DNA probes specific for repetitive pericentromeric regions on chromosomes 6, 8, 17, and human midi-satellite probe specific for one locus on the short arm of chromosome 1 were used to determine chromosome copy numbers in interphase tumor cells. The analysis showed cytogenetic heterogeneity in most nuclei examined with multiple subpopulations and a range of 0-6 chromosome signals per cell. The presence of subclones in these fluids, their correlation with highly malignant phenotypes and the diagnostic and prognostic applications of this method is discussed.