KMT2D is the most frequently mutated epigenetic regulator gene in DLBCL, with its mutation occurring in 24 and 28% of all DLBCL or GCB-DLBCL cases, respectively (Pasqualucci et al., 2011a; Reddy et al., 2017). The gene discussed is KMT2D; the disease is diffuse large B-cell lymphoma.