The mature or peripheral T-cell neoplasms are a heterogeneous group of rare disorders arising from clonal proliferation of mature post-thymic lymphocytes. Natural killer (NK) cells are part of the innate immune system although they have functional similarities to T cells; neoplasms arising from NK cells are considered within the same broad disease group. The World Health Organization (WHO) classification of haemopoietic neoplasms categorised these diseases into those with predominantly leukaemic (disseminated), nodal, extra-nodal or cutaneous presentation. Further delineation is based on clinical features, morphology, immunophenotype and genetics. The 2016 revision of the WHO classification incorporated scientific advances in cell ontogeny and molecular signatures of certain subtypes.1
Declaration of Interests
The BSH paid the expenses incurred during the writing of this guidance. None of the authors had conflicts of interest to declare. All authors have made a declaration of interests to the BSH and Task Force Chairs which may be viewed on request.