Rearrangements of the histone‐lysine‐N‐methyltransferase (KMT2A), previously referred to as mixed‐lineage leukemia (MLL), are among the most common chromosomal abnormalities in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), involving numerous different fusion partners. Here, KMT2A is linked to acute lymphoblastic leukemia.