[Diagnostic challenges in pediatric lymphomas]

Lymphomas in children and adolescents account for only 1-2% of all lymphomas and differ markedly from adult cases in terms of subtype distribution, molecular profiles, and prognosis. This review summarizes current advances in the classification, biology, and diagnosis of pediatric lymphomas, with a focus on rare indolent entities and reactive, lymphoma-mimicking lesions.In addition to the more common entities such as Burkitt lymphoma, lymphoblastic lymphoma (particularly T‑lymphoblastic lymphoma), Hodgkin lymphoma, and ALK-positive anaplastic large cell lymphoma, children may present with rare indolent subtypes including pediatric type follicular lymphoma (PTFL), pediatric nodal marginal zone lymphoma (PNMZL), and testicular follicular lymphoma variants, all of which are associated with excellent prognosis. Aggressive subtypes comprise IRF4-rearranged large B‑cell lymphoma (LBCL-IRF4) and high-grade/large B‑cell lymphoma with 11q aberration (HG/LCBL-11q), both also demonstrating favorable outcomes. Particularly challenging in differential diagnosis are reactive lymphoid proliferations such as infectious mononucleosis, Kikuchi-Fujimoto disease, atypical marginal zone hyperplasia, and progressive transformation of germinal centers (PTGC).Pediatric lymphomas represent a heterogeneous group with specific clinical and biological features. Their diagnosis requires careful consideration to accurately distinguish rare indolent entities, recently defined large B‑cell lymphomas, and reactive mimics. Recent classifications, including the newly introduced WHO Classification of Pediatric Tumors, increasingly reflect these unique aspects.