MLL2 (also known as KMT2D) is mutated in angioimmunoblastic T-cell lymphoma (AITL), PTCL not otherwise specified (PTCL-NOS) [155], DLBCL, FL [156], and NK/T-cell lymphoma (NK/TCL) [157,158], where approximately 91% of mutations result in silencing its histone methylation function [159]. The gene discussed is KMT2D; the disease is mature T-cell and NK-cell non-Hodgkin lymphoma.