Immunological definition of acute minimally differentiated myeloid leukemia (MO) and acute undifferentiated leukemia (AUL).

Immunophenotyping has become an important tool in the diagnosis of acute leukemia for several reasons. Indeed the use of a standardized panel of monoclonal antibodies (MoAb) to B and T cells, and myeloid cells, as well as non lineage restricted antigens, permits allocation of more than 98% of acute leukemia to their respective lineage.1–3 In ALL, immunophenotyping has established a basis for precise and biologically oriented classification of the disease which may be of prognostic importance.2 In AML immunological markers are particularly important for identification of acute leukemia with minimal myeloid, erythroblastic or megakaryoblastic differentiation.Immunological markers also allow the identification of acute leukemias with minimal or aberrant marker expression, acute biphenotypic leukemia in which single cells coexpress different lineage associated markers and acute bilineage leukemia where there are two separate blast cell populations (usually lymphoid and myeloid).3There is sometimes confusion i...