Large B-cell lymphoma with IRF4 rearrangement (LBCL with IRF4 rearrangement) is a DLBCL in which tissue infiltrates containing intermediate- or large-sized neoplastic B-cells strongly express a chromosomal translocation involving the "IRF4" gene on the short arm of chromosome 6. These cells form follicular, follicular and diffuse, or entirely diffuse infiltrates in Waldeyer's tonsillar ring or other regions of the head and neck. The disease, which represents ~0.05% of all DLBCL, occurs primarily in children and young adults and typically has a good prognoses. Cases with a follicular pattern of tissue infiltrates often have indolent disease and an excellent prognosis following excision and may not need chemotherapy. Cases with a purely diffuse tissue infiltrate pattern, in contrast, often do require chemotherapy.