Immunophenotypic characterization of acute leukemias and chronic lymphoproliferative disorders: practical recommendations and classifications.

Immunophenotypic characterization of leukemic cells has become essential for the diagnosis of acute leukemias (AL) and chronic lymphoproliferative disorders (CLPD). Immunophenotyping allows to classify AL according to (i) lineage assignment of the leukemic clone based on the degree of specificity (or "score") of expressed markers, (ii) the differentiation level of the clone and (iii) the presence of irrelevant markers. In addition, some rare AL subtypes may be identified, such as M0, M6 "variant" and M7 FAB types, as well as "biphenotypic" (hybrid) AL. Finally particular immunophenotypic profiles are of pronostic value or associated with specific cytogenetic abnormalities. In leukemic phase CLPD setting, some circulating lymphoid cell immunophenotypic profiles are strongly correlated with morphology as defined by the FAB and REAL classifications. In addition, some marker expressions are of pronostic value. However, proper choices of sample nature, monoclonal antibodies and immunophenotyping methods are essential to improve quality, reliability and reproducibility of the results and must be carefully controlled in and between laboratories.