Acute megakaryoblastic leukemia in a child with the MLL-AF4 fusion gene.

Mixed-lineage leukemia (MLL) rearrangements are commonly observed in childhood acute lymphoblastic and myeloid leukemia, as well as therapy-related leukemia. However, the occurrence of MLL rearrangements in acute megakaryoblastic leukemia (AMKL) is very rare. We report a pediatric case of AMKL with the MLL-AF4 fusion transcript. MLL-AF4 is derived from t(4;11)(q21:q23) and occurs exclusively in B-cell lineage leukemia. To our knowledge, MLL-AF4 as well as t(4;11)(q21:q23) has not been reported in adult and childhood AMKL. Thus, our case provides new insight into the molecular mechanisms of MLL-AF4-associated leukemia.