KMT2A and acute lymphoblastic leukemia: This relatively poorer outcome observed in adult B-ALL compared to childhood cases is partly attributed to the higher occurrence of high-risk molecular lesions, such as BCR-ABL1 (30-40% in adults vs. 2-5% in children) and MLL rearrangements (MLL-r, 10-20% in adults vs. 5-7% in children) 7.