Pediatric Acute Leukemias: Epidemiological, Clinical Features, and Diagnostic Contribution of Flow Cytometry in a Resource-Limited Setting

Introduction: Acute leukemias are the most common hematologic malignancies in children, but detailed epidemiological and immunophenotypic data are limited in Morocco. A better characterization of these diseases is needed to optimize diagnostic strategies. Objective: To describe the epidemiological, clinical, and biological features of pediatric acute leukemias and to evaluate the diagnostic contribution of flow cytometry in a Moroccan university hospital center, based on available diagnostic tools. Methods: We conducted a retrospective, single-center study at the hematology laboratory of Ibn Sina University Hospital, Rabat, including all children under 15 years diagnosed with acute leukemia between January 1, 2022, and January 1, 2024. Diagnosis was based on bone marrow cytology, cytochemistry, and flow cytometry. Cases were classified according to the World Health Organization (WHO) 2008 classification based on the available diagnostic tools, as cytogenetic and molecular studies were not available in our setting. Cytochemical staining for myeloperoxidase (MPO) was systematically performed. Positivity thresholds for flow cytometry followed European Group for the Immunological Characterization of Leukemias (EGIL) recommendations. Statistical analyses used Fisher's exact and Kruskal-Wallis tests, with p < 0.05 considered significant. Results: A total of 106 children with a mean age of 6.9 years were included. Acute lymphoblastic leukemia (ALL) accounted for 81.1% (n = 86), acute myeloid leukemia (AML) for 16.0% (n = 17), and biphenotypic acute leukemia (BAL) for 2.8% (n = 3). Three cases of Burkitt lymphoma were identified and excluded from the ALL group. The overall male-to-female ratio was 1.86 (69 boys, 37 girls), with no significant difference between subtypes (p = 0.46). Subtype distribution varied significantly with age (p = 0.02). The main clinical features were tumor syndrome (84.0%), fever (67.0%), and hemorrhagic syndrome (50.9%). Fever was significantly more frequent in B-ALL than in other subtypes (p < 0.001), as was hemorrhagic syndrome (p = 0.03). Significant differences between subtypes were also observed for leukopenia (p = 0.04), leukocytosis (p = 0.003), pancytopenia (p = 0.03), and major hyperleukocytosis (>100 × 109/L, p < 0.001). Hypercellular marrow was found in 84.4% of cases, with a median blast count of 88% (interquartile range, IQR: 78-92), significantly higher in ALL than in AML (p = 0.008). Immunophenotyping allowed reclassification of six of the 95 MPO-negative suspected ALL cases: four were reclassified as acute myeloid leukemia with minimal differentiation and two as BAL. In addition, one BAL was identified among the 14 MPO-positive cases, raising the total number of BAL to three. Conclusions: Flow cytometry is a valuable tool for the diagnosis of pediatric acute leukemias in resource-limited settings, contributing to the classification of ALL, identification of acute myeloid leukemia with minimal differentiation, and diagnosis of BAL based on cytology, cytochemistry, and immunophenotyping. The high frequency of aberrant antigen expression supports the need for a standardized diagnostic algorithm combining cytology, cytochemistry, and immunophenotyping. Larger prospective studies with cytogenetics and follow-up are needed to refine prognostic value.