AGGRESSIVE NATURAL-KILLER-CELL LYMPHOMA OF THE SMALL-INTESTINE

We report a case of aggressive non-Hodgkin's lymphoma of the small cel l type arising in the small intestine and having a natural killer cell phenotype, Immunophenotyping of frozen tissue sections revealed a lac k of reactivity with the pan-T-cell markers CD3 and CD5, and no reacti on with B-cell markers. Positive staining was obtained with antibodies to CD2, CD7, and CD56, Molecular studies were negative for clonal T g amma,T beta, and immunoglobulin heavy-chain gene rearrangements. Natur al-killer-cell-associated cytotoxin was demonstrated by positive stain ing with an antibody to perforin, a protein present in the granules of large granular lymphocytes. Despite its indolent histologic appearanc e, the aggressive nature of this neoplasm was suggested by the express ion of the activation markers CD38 and CD71, and the nuclear prolifera tion marker Ki67, and confirmed clinically by its rapid recurrence wit h extensive involvement of the pelvic organs, resistance to chemothera py, and the short survival of the patient, Distinct from many Asian ca ses, Epstein-Barr virus genome was not detectable in the tumor, This c ase emphasizes the importance of recognizing non-Hodgkin's lymphomas w ith a natural killer cell phenotype as a distinct entity, both biologi cally and clinically.