Background: Acute leukemias (ALs) are a heterogeneous group of malignancies with various clinical, morphological, immunophenotypic, and molecular characteristics. Distinguishing between lymphoid and myeloid leukemia is often performed by flow cytometry. This study aimed to evaluate the immunophenotypic characterization and expression of immuno-markers in both acute myeloid leukemia (AML-M0) and acute T-cell lymphoblastic leukemia (T-ALL). Methods: A retrospective cross-sectional study was conducted in the Pathology Department/Teaching Laboratories/Medical City/Iraq and included all patients newly diagnosed with AL from 5 January to 10 December 2018. Immunophenotypic analysis was performed on bone marrow samples, freshly collected in EDTA tubes. Flow cytometry (Canto-2 BD) was used, with laser excitation of blue and red wavelengths. A panel of monoclonal antibodies (MoAbs) was used for diagnosis, using a SSC/CD45 gating strategy. Results: The study showed 41.6% of AML-M0 patients had no aberrant antigen expression, while 33.3%, 16.6%,  8.3%, and 8.3% had aberrant CD7, CD56, CD2, and CD19, respectively. In 16.6% of AML-M0 cases more than one aberrant antigen was expressed. With regard to T-ALL, 7.0% were pro-T type, 58.0% were pre-T, 13.0% were cortical, and 22.0% were mature-T type. In 55.5% of patients with T-ALL there was no aberrant antigen expression. Conclusion: We concluded that most patients with AML-M0 have no aberrant antigen expression. In patients with T-ALL, the pre-T type is most common, according to the European Group for the Immunological Classification of Leukemias (EGIL) classification. Patients with T-ALL also generally lack aberrant antigen expression.

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