MLLT1 and acute myeloid leukemia: Even though KMT2A can fuse to a variety of genes, over 90% of KMT2A rearrangements involve nine specific gene fusions, notably fusions to AF4 (AFF1), AF9 (MLLT3), and ENL (MLLT1) accounting for 36%, 19%, and 13% of all AML cases with KMT2A-, respectively [30].