Background: Recent advances in flow cytometrlc technology and the development of monoclonal antibodies have led to important insights into cell lineage and maturation stage of leukemia, Immunophenotyping of acute leukemia has helped to define prognostically significant disease subtypes.
Methods: The immunophenotyping of leukemic cells was analysed uslng flow cytometry in 64 cases with acute Iymphoblastic leukemia, 72 with acute myeloid leukemia, and 5 with mixed lineage leukemia between August 1991 and November 1993 and correlated with the FAB classification and complete remission rate after induction chemotherapy.
Results:
1. Immunophenotypes of ALL : CALLA(+) B ALL were 68.7%(44/64) of ALL cases, CALLA(-) B ALL were 18.8%(12/64), T ALL were 7.8%(5/64), and biphenotypic leukemia were 4.7%(3/64) of ALL cases.
2. Complete remission rate in subgroups of ALL after induction chemotherapy : T ALL had the highest CR rate(75%), followed by CALLA(+) B ALL(66.7%), biphenotypic
leukemia(66.7%), and CALLA(-) B ALL(63.6%).
3. Immunophenotypes of AML : 57.7%(41/71) of AML cases were positive for CDl5, 26.8%(15/56) were CD11c, 62.5%(45/72) were CDl5 &/or CD11c, and 26.6%(17/64) were
CD34 positive. Ly+AML were 33.3% (6/18) of AML cases.
4. Complete remission rate in subgroups of AML after induction chemotherapy Ly+ AML had 33.3%(2/6) CR rate, CDl5 positive AML had 22.3%(8/35), CD34 positive AML had 16,7%(2/12), and CD11c positive AML had 0%(0/10) CR rate after induction chemotherapy.
5. Mixed lineage leukemia : Mixed lineage leukemia were 3.6%(5/141) of acute leukemia cases, and all of those 5 cases did not reach complete remission after induction
chemotherapy.
Conclusion: Immunophenotypes of acute leukemia including biphenotypic leukemia do not have prognostic significance, but mixed lineage leukemia and CD11c positive AML
are predictive of a poor response to induction chemotherapy.

Keywords: Acute leukemia, Immunophenotype, Biphenotypic leukemia, Mixed lineage leukemia,