[23, 25, 26] Loss of function mutations in DNMT3A, a DNA methyltransferase that is required for genome-wide de novo methylation, are frequent in a variety of malignancies and have been reported in up to 38% of PTCL, NOS and 33%-37% AITL. The gene discussed is DNMT3A; the disease is mature T-cell and NK-cell non-Hodgkin lymphoma.