IRF4 and diffuse large B-cell lymphoma: Protein expression in DLCBL in comparison to non-neoplastic B-cells is more complex (Fig. 2), suggesting deregulation of their gene expression, e.g. MUM1 and bcl-6 expression is not exclusive in DLBCL (Falini et al. 2000; Falini and Mason, 2002; Pileri et al. 2002; de Leval and Harris, 2003; Hans et al. 2004).