KMT2D and B-cell non-Hodgkin lymphoma: In various B cell lymphomas, such as diffuse large B cell lymphoma (DLBCL) or follicular lymphoma (FL), somatic mutations in KMT2D (MLL2), EZH2, CREBBP, and TET2 are frequent events, affecting germinal center (GC) formation and affinity maturation [1, 4–6].