KMT2A-MLLT3 is a fusion between the KMT2A (lysine (K)-specific methyltransferase 2A, also known as MLL) gene and the MLLT3 (myeloid/lymphoid or mixed-lineage leukemia (trithorax homolog, Drosophila); translocated to, 3) gene. The KMT2A-MLLT3 fusion has been observed in AML and B lymphoblastic leukemia/lymphoma (Takachi et al. 2011; Metzler et al. 2004). The KMT2A-MLLT3 fusion gene, t(9;11)(p22;q23), results in a protein that prevents normal maturation of hematopoietic cells (Mueller et al. 2009). However, additional mutations are likely required for leukemogenesis (Pession et al. 2003).