IDH2 and mature T-cell and NK-cell non-Hodgkin lymphoma: In myeloid malignancies, TET2 and IDH2 mutations are known to be mutually exclusive.14, 29 However, we and others reported that IDH2 mutations often coexist with TET2 mutations in PTCL.8, 10, 30IDH2 mutations were identified in PD1+ cells but not in CD20+ cells in all 4 TET2- and IDH2-comutated samples (PTCL8, PTCL61, PTCL63 and PTCL70) (Figure 3).