NFKB1 and primary central nervous system lymphoma: It is described that enrichment of mutations involving the B‐cell receptor signaling pathway and hyperactivation of the NF‐kappaB prosurvival signaling pathway (NFkB) are associated with the pathogenesis of PCNSL; however, the rarity of this disease and the paucity of histopathological material available area challenge for molecular studies (Braggio et al., 2015; Rubenstein, 2017).