[Relapsed acute myeloid leukemia concomitant with TET2-mutated peripheral T-cell lymphoma, not otherwise specified].

A 70-year-old female was initially diagnosed with acute myeloid leukemia (AML) and achieved complete remission by conventional chemotherapy. She presented with leukocytosis and pleural effusion six years later, and was diagnosed with myelodysplastic/myeloproliferative neoplasms (MDS/MPN) by bone marrow (BM) analysis. Pyrexia and lymphadenopathy developed one year later, and lymph node biopsy confirmed peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS). Chemotherapy achieved a partial remission. Fifty-two days after her last chemotherapy treatment, increased blasts in the peripheral blood along with marked lymphadenopathy were observed, which were considered to be indicative of the simultaneous development of AML and lymphoma. TET2 mutations were confirmed in BM and lymph node samples. Development of AML and PTCL-NOS might be due to clonal hematopoiesis associated with aging and chemotherapy.