Background: Acute leukemia (AL) is a heterogeneous group of malignancies with varying clinical, morphologic, immunologic, and molecular characteristics. Many distinct types are known to carry predictable prognoses and warrant specific therapy. Hence the distinction between lymphoid and myeloid leukemia, most often made by flow cytometry (FCM), is crucially important. This study was undertaken to evaluate the value of multi-color flow cytometry in the immunophenotyping of acute leukemia in children.

Methods: Three- or four-color flow cytometry and CD45/SSC gating were used to analyze the surface and cytoplasmic antigen expressions from 222 children with acute leukemia.

Results: Cells from the 222 children were analyzed. Based on the diagnostic criteria proposed by EGIL, four categories of the cells could be identified: undifferentiated type, 2 patients (0.9%); acute myeloid leukemia (AML), 78 (35.1%); acute lymphoblastic leukemia (ALL), 124 (55.9%); and mixed lineage AL, 18 (8.1%). Of the 124 patients with ALL, 94 (75.8%) were classified as having B lineage and 30 (24.2%) T lineage ALL. Antigen aberrant expressions were found in 19 (24.4%) of 78 patients with AML, 34 (36.2%) of 94 with B lineage ALL and 9 (30.0%) of 30 with T lineage ALL. The most commonly expressed lymphoid antigen in 78 patients with AML was CD7, 10 patients (12.8%), followed by CD19, 5 (6.4%), and CD2, 4 (5.1%). The most commonly expressed myeloid antigen in 124 patients with ALL was CD13, 23 patients (18.5%), followed by CD15, 14 (11.3%), CD11b, 8 (6.5%) and CD33, 4 (3.2%). CD117 and CD56 were present in 55 (73.3%) and 27 (38.6%) of the 75 patients and 71 patients with AML, respectively, but were generally absent in blast cells of ALL. Cytoplasmic (Cy) CD22, CyCD3 and CyMPO were specifically expressed in B lineage, T lineage and myeloid lineage leukemia, respectively, and the first two could be more sensitively detected than they were on the cell membrane surface.

Conclusions: Multi-color flow cytometry is a reliable technique in the diagnosis, differential diagnosis and classification of acute leukemia in children.