BCL6 (B-cell lymphoma6 protein) is a master regulator of the germinalcenter (GC) B-cell phenotype and is required for GC formation.1−3 By binding to and repressing target genes, BCL6 attenuates celldifferentiation and the DNA-damage response, thereby facilitatingthe process of somatic hypermutation required for antibody maturation.4,5 This phenotype broadly resembles that of malignant cells, so perhapsunsurprisingly, most B-cell lymphomas, including diffuse large B-celllymphoma (DLBCL), derive from GC B-cells. The gene discussed is BCL6; the disease is B-cell non-Hodgkin lymphoma.