The pathology of NK-cell lymphomas and leukemias

Cytotoxic T-cell and NK-cell lymphomas are a group of closely related neoplasms with many clinical, histologic, and immunophenotypic features in common. Most of them are extranodal in origin containing areas of necrosis or apoptotic cells. Several distinct entities have been delineated within this group of lymphoid neoplasms. Extranodal NK/T-cell lymphoma, nasal type is EBV-associated and characterized by aggressive clinical course, high incidence of p53 abnormalities, and high levels of MDR expression. Aggressive NK-cell leukemia/lymphoma has been regarded as a separate nosologic entity characterized by generalized lymphadenopathy, hepatosplenomegaly, the presence of atypical lymphocytes with large azurophilic cytoplasmic granules in the peripheral blood. Blastic or blastoid NK-cell leukemia/lymphoma with CD3(-), CD56(+) medium-sized cells has been also described.