The National Comprehensive Cancer Network (NCCN) guidelines for diagnostic workup of DLBCL patients include: (a) pathological review of lymph node biopsy slides for morphological variants for DLBCL (i.e., centroblastic, immunoblastic, and anaplastic); (b) IHC for CD20, CD3, CD5, CD10, CD45, BCL-2, BCL-6, Ki-67, IRF4/MUM1, and MYC; (c) flow cytometry for kappa/lambda, CD45, CD3, CD5, CD19, CD10, and CD20; (d) PCR for IgH and TCR gene rearrangements, and (e) FISH for major translocations, such as t(8;14), t(14;18), and t(3; v) [30, 38]. This evidence concerns the gene IRF4 and diffuse large B-cell lymphoma.