TET2 and mature T-cell and NK-cell non-Hodgkin lymphoma: Main genes involved in epigenetic regulation are frequently mutated in PTCL, including histone modification (KMT2D, KMT2A, SETD2, KDM6A, EP300, and CREBBP), chromatin remodeler (ARID1B and ARID2) [12], and DNA methylation and demethylation genes (TET2, DNMT3A, and IDH2) [13].