Heterogeneity Among the Acute Nonlymphocytic Leukemias: Value of Immunophenotype for Diagnosis, Prognosis, and Therapy

Immunophenotyping of acute nonlymphocytic leukemia has confirmed previous observations on the heterogeneity of this disease. The lack of leukemia-specific monoclonal antibodies as well as antibodies reactive with early myeloid cells is reflected in poor correlation of morphologically and cytochemically defined FAB classes with the immunophenotype of the leukemic cells. Possible exceptions are the microgranular variant of FAB-M3, megakaryocytic leukemia (FAB-M7), and early erythroid leukemias (FAB-M6). The use of antibody panels can alleviate the differential diagnosis of acute lymphoid and myeloid leukemias, especially those occurring in infants, and the discrimination of FAB-L2 and FAB-MI. Also, the immunophenotyping of presumptive hybrid leukemias can help to resolve the many questions about these leukemias with a particularly poor prognosis. The challenge for multiinstitutional groups is to define those clinically relevant subgroups of acute nonlymphocytic leukemia in children that have general acceptance and could provide the basis for new treatment strategies.