Importantly, among Tfh lymphomas, IDH2R172 mutations are mostly confined to AITL and are rare in FTCL [37] and PTCL-NOS with Tfh phenotype or GEP [31, 33, 37, 38, 40], unlike recurrent mutations in TET2, DNMT3A, and RHOA, which are common to all types of Tfh lymphomas. The gene discussed is DNMT3A; the disease is lymphoma.