An acute leukemia of ambiguous lineage characterized by blasts which coexpress myeloid and T or B lineage antigens or concurrent B and T lineage antigens. (WHO, 2001). The disease is Monarch Disease Ontology identifier MONDO_0020322 (acute biphenotypic leukemia). Also known as: B- and T-cell mixed leukaemia, B- and T-cell mixed leukemia.