Immunophenotyping of acute leukemia – diagnostic approach

The introduction of immunophenotyping in clinical medicine was based on the need for more precise criteria to assist the morphological diagnosis and classification of hematological malignancies, especially acute leukemia (AL). Currently, a comprehensive immunophenotypic analysis of malignant cells provides valuable information for the classification of leukemia and lymphoma based on cell lineage and maturation stage. However, the clinical impact of immunophenotyping differs between the two major forms of AL. While in acute (especially B-precursor) ALL it significantly contributes to diagnosis, classification and prognostic stratification of the disease, its value in the classification of AML is restricted. The reasons for this are the multilineage cell nature and greater immunophenotypic and cytogenetic heterogeneity of AML, the presence of two or more subpopulations in a number of patients, as well as the lack of specific "early" myeloid-lineage markers, In general, the utility of immunophenotyping for subclassification of AML is limited to the identification of poorly differentiated AML, megakaryocytic and the microgranular variant of acute promyelocytic leukemia, mas well as of rare subtypes of dendritic cell neoplasia. mIn other types of AML immunohenotyping is used to confirm the diagnosis. In addition to these standard indications, the immunophenotyping is increasingly being used for the definition of prognostic entities, screening of genetic abnormalities, measurement of minimal residual disease (MRD) and monitoring of specific therapies. These indications are based on the fact that AL cells usually display unusual or aberrant phenotypes, allowing their identification even at very low frequencies. Future studies should take advantage of powerful technology (i.e. multiparameter flow cytometry) combined with new marker combinations to address the potentials of immunophenotyping in the demanding clinical menagement of hematological malignancies.