OBJECTIVETo analyze the clinical and biological characteristics and prognosis of adult biphenotypic acute leukaemia (BAL).

METHODSImmunophenotypes were analyzed using multicolor flow cytometry, karyotype analysis by short-term culture R-banding technique. The chemotherapy regimens were accordingly for acute lymphoblastic leukaemia (ALL), acute myeloid leukaemia (AML) or for both ALL and AML. Patients with Ph (+) or bcr-abl (+) were treated with Imatinib.

RESULTS(1) The incidence of BAL in acute leukaemias was 6.7%, with a male predominance and 52.3% of BAL patients had WBC > or = 30 x 10(9)/L and 16.9% WBC > or = 100 x 10(9)/L. (2) Percentages of coexpression of myeloid and B lymphoid antigens were 81.5%, of myeloid and T lymphoid antigens 10.8%, of myeloid, B- and T lymphoid antigens 4.6%, and of B and T lymphoid antigens 3.1%. (3) Normal and abnormal karyotypes accounted for 41.5% and 58.5%, respectively in 53 BAL patients with karyotype analysis. The rate of Ph (+) or bcr-abl (+) was 32.1%. (4) 31 (56.4%) of 65 patients achieved complete remission (CR), but CR rate was only 35.3% for Ph (+) or bcr-abl (+) cases.

CONCLUSION(1) High white blood cell count and coexpression of myeloid/B lymphoid antigens are common in BAL. (2) Abnormal karyotypes and Ph (+) or bcr-abl( +) often happen. (3) The treatment outcome of BAL is poor.