NASAL NATURAL-KILLER (NK) CELL LYMPHOMA - REPORT OF A CASE WITH ACTIVATED NK CELLS CONTAINING EPSTEIN-BARR-VIRUS AND EXPRESSING CD21 ANTIGEN, AND COMPARATIVE-STUDIES OF THEIR PHENOTYPE AND CYTOTOXICITY WITH NORMAL NK CELLS

Malignant lymphomas arising from the nasal cavity have been considered to be derived from T cells, but recent surface marker studies suggest that more than half of the lymphomas are derived from natural killer (NK) cells. Here we describe a case of nasal lymphoma whose lymphoma c ells were identified as NK cells by morphological, phenotypic, immunog enotypic, and functional studies. We believe this is the first study w ith functional evidence of NK activity. When compared with normal fres hly isolated NK cells or activated NK cells, the surface phenotypes an d Mt activity of the patient tumour cells were those of the activated, but not resting, NK cells. Also, Epstein-Barr virus (EBV) was detecte d in the tumour cells and the lymphoma cells were found to be monoclon ally expanded. The patient's lymphoma cells also expressed EBV recepto r CD21 (CR2) and CD30 (Ki-l) that have not been described on normal NK cells. We therefore examined highly enriched NK cells of normal donor s, and found that some resting and/or activated NK cells express these antigens.