Natural killer cell lymphoma in the duodenum.

We present a case of duodenal non-Hodgkin lymphoma in a 71-year-old woman. Immunohistochemistry characterized the lymphoma cells as CD2(+); surface CD3(-) but cytoplasmic CD3(+); CD7(+); and CD56(+) without a rearrangement of the T-cell receptor gene. Cells had a high N/C ratio and irregular nuclear outlines and lacked azurophilic granules and these features indicated that the lymphoma cells arose from natural killer (NK) cells. She was treated with intensive chemotherapy including pirarubicin, cyclophosphamide, vincristine, and prednisolone, but died three weeks after diagnosis. CD56(+) lymphomas originate from NK or cytotoxic T cells and are designated "extranodal NK/T-cell lymphoma, nasal type" in the WHO classification. Nasal NK cell lymphoma is most common in East Asians and CD56(+) lymphomas usually occur in the nasal area. Extranasal forms such as gastrointestinal lymphomas are very rare and usually carry a poor prognosis. Extranodal NK/T-cell lymphoma, nasal type, is characterized by a broad morphologic spectrum and have variable prognosis. These lymphomas constitute an heterogeneous group, and their subclassification has not yet been established.