BCL6 expression was associated with prognosis in systemic DLBCL, however with contradicting results in PCNSL (Braaten et al., 2003; Camilleri‐Broet et al., 2006; Chang et al., 2003; Momota et al., 2010; Rubenstein, Hsi, et al., 2013). This evidence concerns the gene BCL6 and primary central nervous system lymphoma.