Both lymphocytic gastritis and gastric mucosa associated lymphoid tissue (MALT) lymphoma are associated with Helicobacter pylori (H. pylori) infection. However, this association has not been fully elucidated. We report two cases of lymphocytic gastritis in 57-year-old male and 47-year-old female patients which were diagnosed after the H. pylori eradication to treat gastric MALT lymphoma. MALT lymphoma was successfully treated in case 1, but residual MALT lymphoma remained in case 2. During the follow-up endoscopic examinations, several elevated erosions in case 1 and irregular mucosal atrophy in case 2 were newly detected. Biopsy specimens showed marked infiltration of lymphocytes in the surface epithelium (56.6+/-15.9 intraepithelial lymphocytes (IELs)/100 epithelial cells in case 1 and 40.5+/-9.3 IELs/100 epithelial cells in case 2), which were exclusively CD8-positive T lymphocytes. These findings suggest that H. pylori infection may cause a monoclonal proliferation of B lymphocytes, leading to MALT lymphoma as well as polyclonal proliferation of T lymphocytes which subsequently infiltrated into the surface epithelium as a host immune reaction, resulting in lymphocytic gastritis.
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