Monarch Disease Ontology entry MONDO_0019460 (acute leukemia of ambiguous lineage) is an acute leukemia in which the blasts lack sufficient evidence to classify as myeloid or lymphoid or they have morphologic and/or immunophenotypic characteristics of both myeloid and lymphoid cells. (WHO, 2001). Also known as: acute leukaemia of indeterminate lineage, acute leukemia of indeterminate lineage, hybrid acute leukaemia, hybrid acute leukemia, mixed lineage acute leukaemia, mixed lineage acute leukemia.