Extranodal peripheral T-cell and NK-cell neoplasms.
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.
Jaffe
E S
ES
Hematopathology Section, Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland, USA.
Krenacs
L
L
Kumar
S
S
Kingma
D W
DW
Raffeld
M
M
D006801:Humans; D007694:Killer Cells, Natural; D016399:Lymphoma, T-Cell / Q000145:classification* / Q000453:epidemiology / Q000473:pathology*; D014944:World Health Organization