­­Immunophenotypic Aberrancies in Acute Leukemia: A Tertiary Care Centre Experience

OBJECTIVES: Acute leukemias (AL) are a heterogeneous group of hematological malignancies with the presence of 20% or more blasts in the peripheral blood or bone marrow. Malignant cells display characteristic patterns of surface antigenic expression. Aberrant phenotypes are defined as patterns of antigen expression on neoplastic cells different from the process of normal hematopoietic maturation. We sought to evaluate the occurrence of aberrant phenotypes in newly diagnosed cases of AL. METHODS: The study included 100 patients in whom both bone marrow aspiration and flow cytometry were performed. Patients with blasts > 20% of all ages were included in the study. Flow cytometric analysis was done using the monoclonal antibody panel of peripheral blood/bone marrow. RESULTS: Out of 100 cases, 53 were categorized as acute myeloid leukemia (AML), 43 as acute lymphoid leukemia (ALL), and four cases of mixed phenotypic acute leukemia (MPAL). ALL were subcategorized based on immunophenotyping into B-ALL and T-ALL, which comprised 88.4% and 11.6%, respectively, of total ALL (43.0%) cases. Cluster of differentiation 33 (CD33) and CD13 were the most commonly expressed antigens in AML, with CD7 being the most common aberrancy. CD19 was expressed in all B-ALL cases followed by cCD79a, CD10, Tdt (86.8%) with CD13 being the most common aberrancy. cCD3, CD7, and CD5 were expressed in all T-ALL cases with aberrant antigen expression in 80.0% of T-ALL cases. MPAL cases showed expression of B/myeloid antigens. CONCLUSIONS: The diagnosis and classification of leukemia rely on the simultaneous application of cytomorphology, cytochemistry, flow cytometry, cytogenetics, and molecular techniques. Flow cytometry is of great help in the diagnosis of AL, particularly in ALL for lineage assignment and in classifying MPAL. It also helps in detecting aberrant antigen expression and assisting in minimal residual disease detection.