Clinicopathologic Analysis of Lymphocytic GastritisBackground : Lymphocytic gastritis (LG) is defined as an infiltration of more than 25 intraepithelial lymphocytes (IELs) per 100 surface epithelial cells, and the histological differential diagnosis of LG and residual mucosa associated lymphoid tissue (MALT) lymphoma can be difficult. Helicobacter pylori (H. pylori) is regarded as one of the possible causes of LG, but its clinicopathologic features of LG have not been clarified in Korea, which has a much higher prevalence of H. pylori infection than Western countries. We analyzed the clinicopathologic findings of LG in Korean patients and compared the cytologic findings of IELs of LG with those of MALT lymphoma. Methods : Sixty six cases of LG and 59 cases of MALT lymphoma were selected and clinicopathologic features were analyzed. Results : Eighteen cases (27.3%) of LG were found to be associated with H. pylori infection. The IELs in LG were found to diffusely and regularly infiltrate in the epithelium, but MALT lymphoma showed patchy IELs. IELs in LG and MALT lymphoma were CD 8+T lymphocytes and CD20+B lymphocytes, respectively. The mean nuclear size of IELs in LG was 4.37 m, which was significantly smaller than those in MALT lymphoma (5.19 m). Conclusion : LG, a rare variant of chronic gastritis is partly associated with H. pylori infection and more complex unknown causative factors. In addition to the immunophenotyping, the nuclear sizes of IELs can be helpful in the differential diagnosis of LG and residual MALT lymphoma.