EP300, TET2, and ARID1B mutations had significantly higher proportion in AITL than in PTCL-NOS (22.2% vs. 2.9%, p = 0.043, 50.0% vs. 14.7%, p = 0.010, 33.3% vs. 2.9%, p = 0.003, respectively). The gene discussed is ARID1B; the disease is angioimmunoblastic T-cell lymphoma.