IRF4 and diffuse large B-cell lymphoma: In DLBCL, MUM1 is expressed in 50 to 75% of both Bcl-6+ and Bcl-6− samples, and may reflect derivation from B-cells at a late GC or post-GC stage of differentiation (Fig. 3 and 4C) (Falini et al. 2000; Tsuboi et al. 2000; Natkunam et al. 2001; Pileri et al. 2002; Chang et al. 2004; Hans et al. 2004; Saez et al. 2004; Zinzani et al. 2005).