Alternatively, breakpoints might occur between exon 1 of BCR and exon 2 of ABL1 (e1a2), thus encoding a protein of 190 kDa (p190), which is more frequently found in acute lymphoblastic leukemia (>75%), and more rarely in acute myeloid leukemia (2%) and in CML (<1%) (4, 5). This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.