MYD88, which induces activation of the NF-κB signaling pathway, has been shown to be an important mutation found in PCNSLs in older patients [13,18,53], and it is part of the “MCD” genetic subgroup of extracranial diffuse large B-cell lymphoma (DLBCL); it is defined as the co-occurrence of MYD L265P and CD79B mutations [58]. This evidence concerns the gene NFKB1 and diffuse large B-cell lymphoma.