OBJECTIVETo highlight the current understanding of mixed phenotype acute leukemia (MPAL).

DATA SOURCESWe collected the relevant articles in PubMed (from 1985 to present), using the terms "mixed phenotype acute leukemia", "hybrid acute leukemia", "biphenotypic acute leukemia", and "mixed lineage leukemia". We also collected the relevant studies in WanFang Data base (from 2000 to present), using the terms "mixed phenotype acute leukemia" and "hybrid acute leukemia".

STUDY SELECTIONWe included all relevant studies concerning mixed phenotype acute leukemia in English and Chinese version, with no limitation of research design. The duplicated articles are excluded.

RESULTSMPAL is a rare subgroup of acute leukemia which expresses the myeloid and lymphoid markers simultaneously. The clinical manifestations of MPAL are similar to other acute leukemias. The World Health Organization classification and the European Group for Immunological classification of Leukaemias 1998 criteria are most widely used. MPAL does not have a standard therapy regimen. Its treatment depends mostly on the patient's unique immunophenotypic and cytogenetic features, and also the experience of individual physician. The lack of effective treatment contributes to an undesirable prognosis.

CONCLUSIONOur understanding about MPAL is still limited. The diagnostic criteria have not been unified. The treatment of MPAL remains to be investigated. The prognostic factor is largely unclear yet. A better diagnostic criteria and targeted therapeutics will improve the therapy effect and a subsequently better prognosis.