IRF4 and diffuse large B-cell lymphoma: According to the immunohistochemical cell of origin classification (COO) [16, 28], two DLBCL, NOS cases were of the germinal center B cell (GCB) category (CD10 + IRF4/MUM1−; patient 20, 22) and two cases had a non-GCB phenotype (CD10-IRF4/MUM1+; patient 04, 05; Table 2).