Pediatric lymphomas: overview and diagnostic challenges

Only 10% of new lymphoma diagnoses in the USA occur in children < 15 years. Although the same diagnostic criteria apply to both adult and pediatric lymphomas, there are important differences in some lymphoma subtypes. These differences are recognized by the World Health Organization (WHO) with the recent 2022 classification of pediatric tumors including pediatric hematopoietic tumors. Here, we review the WHO classification scheme for pediatric lymphomas and summarize the diagnostic criteria, recent genetic findings, and differences from their adult counterparts for some subtypes including those yet to be included as a definitive subtype. In general, there are differences in relatively frequency, genetic mutation, and prognosis with the pediatric counterpart often having better prognosis. Emerging B-cell lymphomas with recurrent gene alterations such as IRF4 rearrangement and 11q gain/loss chromosomal alterations will be reviewed. The overlapping pathological, clinical, and molecular features between pediatric-type follicular lymphoma (PTFL) and pediatric nodal marginal zone lymphoma (PNMZL) suggesting one disease with broad morphological spectrum will be discussed. The pathogenetic role of EBV in subclassifying Burkitt lymphoma is highlighted. The revised classification of the EBV-positive lymphoproliferative disorders in children is discussed. This review will focus on novel findings, areas of special interest, and diagnostic challenges in pediatric lymphomas.