Moreover, a study using bacterial artificial chromosome (BAC) array comparative genomic hybridization on CML cell lines and patients [9] revealed unexpected gains of the 9q34 region affecting BCR/ABL1 fusion and part of the sequences telomeric to the fusion gene, which could not be explained as due to a simple duplication of the Ph chromosome. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.