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NK-Cell Lymphomas and Leukemias
A Spectrum of Tumors With Variable Manifestations and Immunophenotype

Robert P. Hasserjian MD, Nancy Lee Harris MD
DOI: http://dx.doi.org/10.1309/2F39NX1AL3L54WU8 860-868 First published online: 1 June 2007


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 EN-NK/T-NT, classification of tumors that have atypical or discordant features will remain controversial, particularly when EBV is absent.

Key Words:
  • Natural killer cell
  • T cell
  • Lymphoma
  • Leukemia