Pathogenesis and Classification of Primary Central Nervous System Lymphoma: An Update

Primary central nervous system lymphoma has undergone a remarkable increase in incidence over the last decade, both in immunosuppressed and immunocompetent individuals. Its clinicopathologic evaluation requires knowledge of current hema‐topathologic systems for lymphoma classification, as well as specific understanding of unique central nervous system determinants. In immuno‐compromised individuals, the tumor has a constant association with Epstein‐Barr virus. The form of Epstein‐Barr virus in these tumors appears to be predominantly latent, however, the precise mechanism relating virus to tumor pathogenesis is still unclear. In immunocompetent patients, risk factors and oncogenic associations are completely unknown. Critical to the formation of these tumors is the trafficking of B‐cells, whether pre‐ or post‐transformation, across the blood‐brain barrier. These B‐cell migrations may require perturbations to the barrier that originate in or around neural parenchyma, such as localized injury or infection.