Primary central nervous system lymphomas in children and adolescents

Abstract

Primary central nervous system lymphoma (PCNSL) is a rare and aggressive neoplasm usually of B-cell origin. Its occurrence is associated with age, with PCNSL affecting more often elderly patients. In adults, PCNSL is a non-germinal center B-cell lymphoma characterized by C5/MCD/MYD88 gene signature, and HLA I/II expression alterations. The disease behaviour differs in children, adolescent, and young adults (CAYA) or in those with an inborn or acquired immune dysregulation/dysfunction, with greater variety of histologic subtypes. Also, different genetic signatures are observed in younger patients (MYD88 wildtype) or in those with EBV+ tumours, including higher frequency of abnormalities in checkpoint inhibitor axes, suggesting different tumour microenvironment compositions and immune escape mechanisms. Children, adolescents and young adults (CAYA) with PCNSL demonstrate more favourable outcomes, likely reflecting a superior response to therapy, whereas outcomes in adult patients remain comparatively poor. Focused research that specifically includes CAYA PCNSL is necessary to uncover additional unique molecular features and association with the immune system in an “immune-privileged” site such as the CNS. These efforts will likely lead to better diagnostic methods, prognostication and optimization of treatment protocols in children, and adolescents with PCNSL.