Activating mutations of NOTCH1 are present in at least 60% of T-ALL [7], while rare additional rearrangements result in the expression of chimeric fusion genes involving Lysine Methyltransferase 2A (KMT2A)/Mixed Lineage Leukemia 1 (MLL1), HOXA genes, and tyrosine kinase genes such as Abelson murine leukemia viral oncogene homolog 1 (ABL1) [32,33]. Here, KMT2A is linked to acute lymphoblastic leukemia.