ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: While B-cell receptor (BCR)-ABL1 fusion protein following the Philadelphia translocation t (9; 22) (q34; q11.2) is a hallmark of chronic myeloid leukemia and is also common in precursor B-cell ALL (B-ALL) [158], BCR-ABL1-positive T-ALL patients are exceptionally rare [159].