Most CML patients present a BCR-ABL1 fusion downstream of exons 13 and 14 of the BCR gene, originating transcripts with an e14 and/or an e13 junction, which drive the expression of a 210 kDa chimeric protein designated p210 BCR-ABL1 (M-BCR), although other isoform fusion proteins (namely p190 and p230) have also been described at lower frequencies in some patient subtypes [2,3,4,5,6]. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.