Mixed phenotypic acute leukemia with two immunophenotypically distinct blast populations: report of an unusual case.

Mixed phenotypic acute leukemia (MPAL) is a rare disorder with an incidence of less than 2% of all acute leukemia using the recent 2008 WHO criteria. Common subtypes encountered are the B/myeloid and T/myeloid; B/T or trilineage MPAL being an exception. We discuss here a case of 20-year-male patient who presented with pallor and generalised lymphadenopathy. Peripheral blood smear examination showed presence of 61% blasts of lymphoid morphology. Immunophenotyping by multicolor flow cytometry showed two distinct populations of blasts with T and B phenotype respectively. He was diagnosed as MPAL with two distinct blast lineages. Conventional karyotyping done on bone marrow sample showed t(9;22)(q34;q11)(Ph +). Induction was started using ALL based protocol. The patient is on follow up with post induction marrow being in morphological remission.