How should pathologists identify large B-cell lymphomas with IRF4-R? It is recommended that all DLBCL and FL 3B cases seen in the pediatric, adolescent, and young adult population (< 40 yrs) that coexpress BCL6 and MUM1 be screened for IRF4-R as is supported by a recent study [57]. The gene discussed is IRF4; the disease is B-cell non-Hodgkin lymphoma.