Immunophenotypic analysis in acute leukemia

Acute leukemias have been classified on French-American-British (FAB) criteria depending on the morphocytochemical features of blasts. Immunophenotyping and clonal rearrangement analysis of lineage-associated genes can decide a frozen stage of the hematopoietic differentiation process in blasts from acute leukemias. B-lineage acute lymphoblastic leukemia (ALL) and T-lineage ALL are systematically classified according to the sequential expression of differentiation-associated antigens. In acute myelogenous leukemia (AML), several new entities are proposed: AML-M0 is an AML without cytologic maturation, in which the myeloid commitment should be demonstrated by myeloperoxidase-positive microgranule on immunohistochemical staining or electron-microscopy, or by positive reaction for CD13 or CD33 antigens. CD7-positive AML is considered to be one of immature subtypes of AML, rather than hybrid leukemia. Thus, immunological studies on blasts enable us to discriminate a subgroup of leukemias, which will perhaps contribute to the improvement of treatment approach.