Clinicopathological and Immunophenotypic Analysis of Early T‐Cell Precursor Acute Lymphoblastic Leukemia With Application of the Tokyo Children's Cancer Study Group Flow Cytometry Scoring System

INTRODUCTION: Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) is a distinct subtype of T-ALL defined by an immature immunophenotype and unique molecular features. It is often associated with chemoresistance and poor outcomes. Accurate recognition is crucial for therapy optimization and consideration of hematopoietic stem cell transplantation. This study evaluated the Tokyo Children's Cancer Study Group (TCCSG) six-marker flow cytometric scoring system in identifying ETP-ALL and assessed its clinicopathological features and treatment outcomes. METHODS: All consecutive T-ALL cases diagnosed between 2019 and 2023 were retrospectively analyzed. Clinical, immunophenotypic, and treatment-related data were compared between ETP-ALL and non-ETP-ALL subgroups. The TCCSG six-marker scoring system (CD34, HLA-DR, CD8, CD5, CD13, CD33) was applied, and receiver operating characteristic curve analysis determined the optimal cutoff for diagnosis. RESULTS: /L), fewer peripheral blasts, and higher platelet counts (p < 0.05). At end-of-induction (EOI), complete remission rates were lower in ETP-ALL (73.3% vs. 96.6%; p = 0.014), though no significant differences were observed in EOI measurable residual disease, consolidation response, or survival between the groups. A cutoff score ≥ 3 using the TCCSG system yielded 88% sensitivity and 94.9% specificity (AUC = 0.986; p = 0.0001). CONCLUSION: ETP-ALL represents a biologically distinct T-ALL subtype with inferior early treatment responses. The TCCSG six-marker scoring system is reliable, accurate, and practical for routine diagnosis, particularly in resource-limited settings.