As recurrent mutations in ATM and p53 related molecules have been identified in other studies of PTCL, we scanned our data for mutations in this pathway and identified mutations in several related genes: TP53, BRAT1, CREBBP, MAPK9, MAPK14, NFKBIA, and TLK1. p53 contained mutations in one case of PTCLnos and one of ATLL, encoding amino acid changes V41M and D10Y, respectively. The gene discussed is MAPK9; the disease is mature T-cell and NK-cell non-Hodgkin lymphoma.