Primary central nervous system diffuse large B-cell lymphoma has poorer immune cell infiltration and prognosis than its peripheral counterpart

Aims Primary central nervous system (CNS) diffuse large B‐cell lymphoma (PCNSL) is an ominous disease with a poor prognosis. The brain is an immune‐privileged sanctuary, and this may contribute to an ineffective host immune response and thus a poorer outcome. The aim of this study was therefore to study the difference in the immune composition in PCNSL and non‐CNS diffuse large B‐cell lymphoma (DLBCL), and the role of the immune response in PCNSL prognosis. Methods and results Thirty‐two biopsy specimens of PCNSL and 30 specimens of low‐stage non‐CNS DLBCL from immunocompetent patients formed the study group. The density and distribution of immune cells, including dendritic cells (dendritic cell‐specific lysosomal‐associated membrane protein‐positive and S100‐positive), effector/memory T cells (CD45RO‐positive), and cytotoxic T cells (granzyme B‐positive), and the expression of HLA‐DR by lymphoma cells, were evaluated immunohistochemically. PCNSL patients showed poorer overall survival (P = 0.032). On comparison of the PCNSL and DLBCL biopsy specimens, the PCNSL cells showed less HLA‐DR expression (P = 0.003), and there were fewer S100‐positive cells (P