BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Fusion of BCR exon 13 or 14 (e13/e14) with ABL1 exon 2 (a2) forms a fusion gene referred to as e13a2 (b2a2) or e14a2 (b3a2), leading to the P210BCR-ABL1 protein (M-bcr) seen in the majority of CML patients [17, 18].