HEMATOLOGICAL AND EPIDEMIOLOGICAL PROFILE OF PEDIATRIC ACUTE LYMPHOBLASTIC LEUKEMIA WITH THE T(1;19) TCF3::PBX1 TRANSLOCATION

Acute Lymphoblastic Leukemia (ALL) is the most common pediatric neoplasm and the leading cause of cancer-related death in children worldwide. In ALL, gene fusions are genetic variants that contribute to tumorigenesis, and the detection of the specific molecular biomarker is a key element in disease diagnosis. Among these gene fusions is TCF3::PBX1 t(1;19), which accounts for approximately 3–5% of pediatric ALL cases and is associated with poor prognosis and increased risk of central nervous system (CNS) infiltration. The TCF3 gene encodes transcription factors regulating B-cell development, whereas PBX1 controls genes related to the hematopoietic system. This study aimed to evaluate the hematological profile of pediatric patients diagnosed with ALL carrying the TCF3::PBX1 biomarker. The study was approved by the Research Ethics Committee under protocol number 4.040.805 and included a total of 44 patients diagnosed with ALL and the t(1;19) translocation at the Hospital Oncológico Infantil Octávio Lobo between 2017 and 2025. Clinical data (white blood cell count, platelet count, and hemoglobin levels) and epidemiological data (sex and age) were retrieved from the hospital database. For biomarker analysis, cDNA was obtained for detection by conventional PCR using specific primers. Agarose gel electrophoresis was performed for visualization of PCR products, and Sanger sequencing was subsequently conducted to confirm PCR results. Descriptive statistics were used for qualitative variables, determining absolute and relative frequencies. For quantitative variables, median values and standard deviations were calculated. ANOVA was applied to assess associations between age groups, according to NCI risk criteria, and clinical data, adopting a p-value ≤ 0.05 as statistically significant. Statistical analyses were performed using RStudio 12.1. Regarding sex distribution, 65% of patients were male and 35% female. The median age was 7 years. Median white blood cell count was 19,350/mm 3 , median platelet count was 31,000/mm 3 , and median hemoglobin level was 8 g/dL. ANOVA revealed no statistically significant differences between NCI age- based risk groups (1–6 years, 6–10 years, and >10 years) and the evaluated hematological parameters. Studies conducted in Nordic countries, Egypt, China, and Mexico have reported a higher prevalence of females with t(1;19), differing from our findings, which revealed male predominance (ratio 1.86:1). In terms of age, previous reports indicate a median of 5–8 years for patients with the TCF3::PBX1 biomarker, consistent with our observations. Regarding leukocyte count, literature shows a median of approximately 22,000/mm 3 in such patients, aligning with the present study and reinforcing the association of this gene fusion with an unfavorable prognosis during ALL treatment.Conclusion: The TCF3::PBX1 gene fusion activates genes encoding proteins with malignant potential and may also lead to CNS involvement. Further investigation into the leukemogenic mechanisms of this biomarker is warranted. In this cohort, 7% of patients were classified as high-risk according to NCI guidelines due to age >10 years combined with a white blood cell count >50,000/mm 3 .