To further assess the performance of FISH probes targeting small genomic loci in MM cell lines, we assessed the human MM cell lines LP-1, U266, and NCI–H929 (characterized by hyperdiploidy with 61–69 chromosomes and a variety of structural abnormalities) and the CML cell line K562 (characterized by hyperdiploidy and multiple BCR-ABL fusion gene amplifications). The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.