Comparative Evaluation of the Immunophenotypic Profile of Acute Lymphoblastic Leukaemia in Adult and Paediatric Age Groups in Iraq

Background: Immunophenotyping is a primary tool for investigating acute lymphoblastic leukemia (ALL). Acute lymphoblastic leukemia accounts for 75 - 80% of pediatric leukemia cases and 14% of adult leukemia cases. However, the prognostic factors, treatment strategies, and pathogenic pathways differ between these groups. Objectives: This study aims to compare the pattern of antigen expression between adult and pediatric ALL patients in the Iraqi population and to evaluate the frequency of aberrant myeloid antigen expression in both groups. Methods: A total of 131 patients with de-novo ALL were studied from May 2014 to May 2015. The diagnosis of ALL was confirmed by morphology and immunophenotyping of peripheral blood and bone marrow aspirate specimens using a panel of fluorochrome-labeled antibodies in 6 - colored flow cytometry. Results: The B-ALL phenotype was prevalent in 44 (68.7%) of adult patients compared to 51 (76.1%) in the pediatric group. CD10 expression was present in 49 (76.6%) of adults, mostly with B-ALL. The pediatric group had lower CD10 expression in T-ALL (P = 0.039). CD20 expression was significantly lower in adults compared to children. In T-ALL, significant differences between adult and pediatric groups were observed in CD1a and CD2 expression. Aberrant myeloid antigen expression was present in 29 (45.3%) adults and 30 (44.8%) pediatric patients, with CD33 and CD13 being the most prevalent in both groups. Conclusions: There was an increased T-cell lineage and aberrant antigen expression in both adult and pediatric ALL cases in this Iraqi sample. Adults with ALL tend to display higher levels of CD20 and lower levels of CD1a and CD2 compared to children, markers associated with poorer prognoses.