title: Extranodal peripheral T-cell and NK-cell neoplasms.
abstract: Mature or peripheral T-cell lymphomas are uncommon, accounting for only 10% to 15% of all non-Hodgkin lymphomas, and their classification has been controversial. In contrast to B-cell lymphomas, cytologic features have not been useful in defining disease entities, and cytologic grade has not been useful in predicting the clinical course. Similarly, many entities of T-cell or NK-cell derivation do not have a specific immunophenotype. Clinical features are of major importance, sometimes more important than the precise cell of orgin, in defining T-cell and NK-cell neoplasms. Most extranodal T-cell/NK-cell lymphomas have a cytotoxic phenotpye. The expression of cytotoxic molecules may predispose to apoptosis by tumor cells and normal bystander cells. Three major categories of extranodal T/NK cell tumors are nasal, intestinal, and subcutaneous panniculitis-like. Hepatosplenic gamma delta T-cell lymphoma is a more systemic disease derived from functionally immature cytotoxic cells. Many extranodal T-cell and NK-cell neoplasms are associated with Epstein-Barr virus (EBV); the association seems site dependent and shows some geographic variation. Tumors resembling any of the 3 prototypes may occur in a variety of extranodal sites. Extranodal T/NK cell lymphomas occur with increased frequency in the setting of immune suppression, especially after organ transplantation.
authors.affiliation: Hematopathology Section, Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland, USA.
authors.forename: E S
authors.initials: ES
authors.lastname: Jaffe
authors.forename: L
authors.initials: L
authors.lastname: Krenacs
authors.forename: S
authors.initials: S
authors.lastname: Kumar
authors.forename: D W
authors.initials: DW
authors.lastname: Kingma
authors.forename: M
authors.initials: M
authors.lastname: Raffeld
mesh_terms: D006801:Humans; D007694:Killer Cells, Natural; D016399:Lymphoma, T-Cell / Q000145:classification* / Q000453:epidemiology / Q000473:pathology*; D014944:World Health Organization