OBJECTIVETo investigate the clinical and biological characteristics and prognosis of mixed phenotype acute leukemia (MPAL).

METHODSThirty two patients were diagnosed as MPAL by bone marrow examination, immunophenotyping, cytogenetic and molecular assay and were treated with combined chemotherapy regimens for both acute lymphoblastic and acute myeloid leukemia. Two cases were received allogeneic hematopoietic stem cell transplantation (allo-HSCT).

RESULTS(1) The incidence of MPAL in acute leukemias was 2.6%. There were 16 cases (50.0%) of mixed myeloid and B-lymphoid (M/B), 14(43.8%) myeloid and T-lymphoid (M/T), one each (3.1%) of trilineage (M/B/T) and B- and T-lymphoid (B/T) phenotype. (2) The positive rates of CD34 and HLA-DR were 87.5% and 62.5%, respectively. (3) Abnormal karyotypes were detected in 70.0% of 30 MPAL patients, which were structural and numerical abnormalities including t(9;22), 11q23 and complex karyotypes. (4) The total complete remission (CR) rate was 75.0% and the overall survival (OS) and disease-free survival (DFS) at 2 years were 14.8% and 14.2% respectively. The CR rates for M/B and M/T cases were 75.0% and 71.4% respectively. No statistical difference was observed in OS and DFS between M/B and M/T cases.

CONCLUSIONSMPAL is a rare type of acute leukemia with a high heterogeneity. The unfavorable indicators of MPAL may be factors such as abnormal karyotypes, high expression of CD34 and extramedullary infiltration. Combined regimens and more intensive therapy including allo-HSCT might contribute to improving survival.