Primary Bone Mature B-cell Non-Hodgkin Lymphomas in Children and Adolescents A French Society of Pediatric Oncology (SFCE) Study

Background:Primary bone mature B-cell lymphomas (PB-BCL) are rare in children and adolescents. Current data on their clinical presentation, management, and outcomes remain limited. The aim of the study was to describe the clinical and radiological characteristics and outcomes of pediatric patients with PB-BCL using data from a multicenter French cohort.Procedure: The team retrospectively analysed data from paediatric patients diagnosed with PB-BCL between 1998 and 2022 and treated according to national protocols (FAB LMB 96, LMB 2001, Inter-B-NHL Ritux 2010). Clinical, imaging, pathological, and therapeutic data were collected. Event-free survival (EFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Results: The cohort included 21 patients, with a male predominance (62%) and a median age at diagnosis of 13 years (3-19). Diffuse large B-cell lymphoma accounted for 66.6% of cases, and Burkitt lymphoma for 28.6%. Lesions were predominantly located in the lower limbs. Multifocal bone involvement was observed in 38.1% of patients and 38.1% were classified as stage III at diagnosis. All patients have been treated with FAB/LMB chemotherapy, with 5 patients receiving Rituximab. After a median follow-up of 3.3 years (0.15 - 19.6), 5-year OS and EFS were 94.5% and 89.7%, respectively. Evaluation of remission and follow-up strategies varied between centers. Conclusions : PB-BCL in children is associated with an excellent prognosis under current treatment protocols, even in advanced-stage disease. However, standardization of remission assessment and post-treatment surveillance remains necessary. Molecular profiling may help improve the understanding of this rare entity.