Primary central nervous system lymphomas associated with chronic inflammation: diagnostic pitfalls of central nervous system lymphomas

In recent years, the features of lymphomas associated with chronic inflammation, referred to as diffuse large B-cell lymphoma (DLBCL) associated with chronic inflammation (DLBCL-CI), have been elucidated. DLBCL-CI is an aggressive lymphoma occurring in the context of long-standing chronic inflammation and showing an association with Epstein–Barr virus. Fibrin-associated diffuse large B-cell lymphoma (F-DLBCL) was suggested as a new and unusual form of DLBCL-CI in the most recent version of the World Health Organization classification. From the perspective of genetics, DLBCL-CI was associated with frequent TP53 mutation, MYC amplification and complex karyotypes, but cases of F-DLBCL behaved indolently and showed a relatively lower genetic complexity. In the central nervous system (CNS), several examples of DLBCL-CI and F-DLBCL have been reported. As with DLBCL-CI outside the CNS, DLBCL-CI in the CNS is an aggressive lymphoma. However, the clinical outcome of F-DLBCL in the CNS is good. Immunohistochemistry for p53 and c-Myc in DLBCL-CI and F-DLBCL in the CNS showed similar findings of those outside the CNS. However, one aggressive case showed transitional genetics and morphology between F-DLBCL and DLBCL-CI. These findings suggest that some cases of F-DLBCL in the CNS might have the potential to progress to DLBCL-CI.