Acute Megakaryoblastic Leukemia Associated with Trisomy 21 Demonstrates a Distinct Immunophenotype

Background: Acute megakaryoblastic leukemia (AMKL) is a rare form of acute myeloid leukemia that encompasses three distinct subgroups, children with Down syndrome (DS-AMKL), children without DS (non-DS-AMKL) and adults (adult-AMKL). We hypothesize that the biological differences in the subtypes of AMKL may be reflected in distinct immunophenotypic (IP) features. Our aims were to employ mutiparameter flow cytometry to establish a comprehensive IP spectrum of AMKL in multiple demographic groups and to determine whether the subtypes of AMKL demonstrate distinct immunophenotypes. Methods: Thirty-seven AMKL cases were retrieved and subdivided into these three groups. Multiparameter flow cytometry was used to determine and compare the immunophenotypes. Available clinical, cytogenetic, and morphologic data were reviewed to confirm diagnoses. Results: While there is commonality in the expression pattern for a wide range of myelomonocytic markers in these three subtypes of AMKL, blasts in DS-AMKL were more likely to express CD7 and CD11b than those in non-DS-AMKL and adult-AMKL. Furthermore, blasts in DS-AMKL were more likely to express CD13, CD33 and CD36 than non-DS pediatric AMKL, and showed greater CD56 expression compared to adult AMKL. Conclusions: These results indicate that DS-AMKL is related to but immunophenotypically distinct from non-DS-AMKL and adult-AMKL. This distinct immunophenotypic pattern, co-expression of CD7 and CD11b, has practical implications for characterization of AMKL. © 2014 Clinical Cytometry Society.