An extremely rare case of primary gastrointestinal T-cell lymphoma inv
olving the stomach and intestine is reported. Radiographic and endosco
pic examinations showed multiple polypoid lesions covered by a normal-
appearing mucosa in the stomach, duodenal bulb, and terminal ileum and
numerous small aphthoid lesions throughout the entire colorectum. His
topathologic, immunohistochemical, and polymerase chain reaction studi
es were performed using paraffin-embedded or fresh-frozen specimens fr
om endoscopic biopsies and endoscopic mucosal resections. All lesions
were composed of small, atypical lymphoid cells, which were classified
as low-grade pleomorphic lymphoma. The tumor cells expressed CD3, CD4
, and the T-cell receptor gamma gene phenotype as well as human mucosa
l lymphocyte 1 antigen, suggesting that the lymphoma cells were derive
d from intraepithelial T lymphocytes. This is the First description of
primary gastrointestinal T-cell lymphoma with expression of human muc
osal lymphocyte 1 antigen and a novel morphology resembling multiple l
ymphomatous polyposis.