title: NK-cell lymphomas and leukemias: a spectrum of tumors with variable manifestations and immunophenotype.
abstract: Natural killer (NK) cells are lymphocytes that have some phenotypic and functional similarities to cytotoxic T cells but do not express the T-cell receptor complex. NK-cell malignancies may be localized or disseminated at initial examination, and most behave aggressively. The variable presentation of NK-cell lymphomas and leukemias suggests that they represent a spectrum of disease, with Epstein-Barr virus (EBV) implicated in the pathogenesis of most cases. Using cases presented in Session 10 of the 2005 Society for Hematopathology/European Association for Haematopathology Workshop on T-cell and NK-cell malignancies, we discuss outstanding issues in the classification and diagnosis of NK-cell malignancies. These difficulties are related to unusual sites of manifestation, atypical immunophenotypic features, and EBV+ T-cell tumors that resemble classical extranodal NK/T-cell lymphoma, nasal-type (EN-NK/T-NT). Although some of these cases can be grouped into ENNK/T-NT, classification of tumors that have atypical or discordant features will remain controversial, particularly when EBV is absent.
authors.affiliation: Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Hasserjian
authors.forename: Nancy Lee
authors.initials: NL
authors.lastname: Harris
mesh_terms: D020031:Epstein-Barr Virus Infections / Q000150:complications / Q000276:immunology / Q000473:pathology; D004854:Herpesvirus 4, Human / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity; D006801:Humans; D016130:Immunophenotyping; D007694:Killer Cells, Natural / Q000473:pathology*; D007938:Leukemia / Q000276:immunology / Q000473:pathology* / Q000821:virology; D008228:Lymphoma, Non-Hodgkin / Q000276:immunology / Q000473:pathology* / Q000821:virology; D012367:RNA, Viral / Q000302:isolation & purification; D013601:T-Lymphocytes / Q000473:pathology*
chemical_list: D012367:RNA, Viral