Immunophenotype and Relevance to the WHO Classification The immunophenotype of human leukemia cells can be studied by multiparameter flow cytometry after the cells are labeled with monoclonal antibodies to cell-surface antigens. This can be important for separating AML from acute lymphoblastic leukemia (ALL) and identifying some types of AML. For example, AML that is minimally differentiated (immature morphology and no lineage-specific cytochemical reactions) is diagnosed by flow-cytometric demonstration of the myeloid-specific antigens cluster designation (CD) 13 or 33. Similarly, acute megakaryoblastic leukemia can often be diagnosed only by expression of the platelet-specific antigens CD41 and/or CD61. While flow cytometry is. | Chapter 104. Acute and Chronic Myeloid Leukemia Part 3 Immunophenotype and Relevance to the WHO Classification The immunophenotype of human leukemia cells can be studied by multiparameter flow cytometry after the cells are labeled with monoclonal antibodies to cell-surface antigens. This can be important for separating AML from acute lymphoblastic leukemia ALL and identifying some types of AML. For example AML that is minimally differentiated immature morphology and no lineage-specific cytochemical reactions is diagnosed by flow-cytometric demonstration of the myeloid-specific antigens cluster designation CD 13 or 33. Similarly acute megakaryoblastic leukemia can often be diagnosed only by expression of the platelet-specific antigens CD41 and or CD61. While flow cytometry is useful widely used and in some cases essential for the diagnosis of AML it is only supportive in establishing the different subtypes of AML through the WHO classification. Clinical Features and Relevance to the WHO Classification The WHO classification considers clinical features in subdividing AML. For example it identifies therapy-related AML as a separate entity and subclassifies this group based on the specific types of prior chemotherapy received. It also divides AML with multilineage dysplasia based upon the presence or absence of an antecedent MDS. These clinical features contribute to the prognosis of the specific type of AML. Genetic Findings and Relevance to the WHO Classification The WHO classification is the first AML classification to incorporate genetic chromosomal and molecular information. Indeed AML is first subclassified based on the presence or absence of specific recurrent genetic abnormalities. For example AML FAB M3 is now designated acute promyelocytic leukemia APL based on the presence of either the t 15 17 q22 q12 cytogenetic rearrangement or the PML RARa product of the translocation. Thus the WHO classification separates APL from all other types of AML as a first step
