Cytogenetic analysis and FISH experiments with specific BAC/PAC probes for the ABL1 and BCR genes allowed us to detect 50 (11.1%) out of 452 cases, that identify 3 main subgroups of CML patients showing variant t(9;22) rearrangements, the occurrence of cryptic insertions of the ABL1 in the BCR region (or vice versa), and the presence of additional chromosomal abnormalities, respectively (Table 1). This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.