T- and NK-cell lymphomas are neoplasms derived from immature T cells (lymphoblastic lymphomas), or more commonly, from mature T and NK cells (peripheral T-cell lymphomas, PTCLs). PTCLs are rare but show marked biologic and clinical diversity. They are usually aggressive and may present in lymph nodes, blood, bone marrow or other organs. More than 30 T/NK-cell derived neoplastic entities are recognized in the International Consensus Classification and the classification of the World …