Aberrant phenotypes in acute myeloid leukemia: a high frequency and clinical significance

Background and Objectives. Immunophenotyping is an essential method for dia gnosis and classification of acute myeloid leukemias (AML), and its extensi ve use could identify blast cell subpopulations with aberrant phenotypes ra rely seen in normal myelopoiesis. The aberrant phenotypes have been correla ted with clinical, morphologic and prognostic features but their occurrence in AML differs in the various studies. Design and Methods. In this study we analyzed 35 cases of AML, examining th em for aberrant phenotypes by multiparametric flow cytometry. Co-expression of lymphoid-associated markers in myeloblasts and asynchronous antigen exp ression were correlated with clinical features. Results. Aberrant phenotypes were found in 88.6% of the cases studied. In t his group, cross-lineage antigen expression was present in 34.3% and asynch ronous expression in 82.4% of the cases. CD7 was the most frequent lymphoid -associated antigen. Among the cases of asynchronous antigen expression, th e most frequent phenotype was CD117(+) and/or CD34(+) in association with C D11c(+), followed by CD15(+) and CD65(+), corresponding to 67.6%, 61.7% and 50.0% of the cases, respectively. Twenty out of 33 patients were available for complete remission assessment. The CD117+ CD15+ phenotype correlated s ignificantly with complete remission achievement and with the lack of unfav orable chromosome associations. Interpretation and Conclusions. We conclude that aberrant phenotypes, as th ey are described here, are present in the great majority of cases of AML, a synchronous antigen expression being the most frequent example, and that CD 117+ CD15+ phenotype shows a relevant association with clinical prognosis. (C) 2001, Ferrata Storti Foundation.