BACKGROUND: Lymph node metastasis is a frequent type of metastasis in patients with gastric cancer. The mechanisms responsible for this type of metastasis, however, are not clearly understood. We hypothesize that the immunosurveillance system between cancer cells and lymphocytes may be associated with the lymph node metastatic process. In this study, we examined the correlation between lymph node metastasis and intercellular adhesion molecule-1 (ICAM-1), which mediates the immunosurveillance system between tumor cells and cytotoxic lymphocytes, in gastric cancer.METHODS: One hundred and forty-three specimens resected from patients with gastric cancer were investigated by staining with a monoclonal antibody against ICAM-1. We studied the correlation between the expression of ICAM-1 and various clinicopathologic factors, as well as infiltration of tumor-infiltrating lymphocytes (TILs).RESULTS: ICAM-1 expression on gastric cancer cells was significantly decreased in patients with lymph node metastasis. The infiltration of TILs was associated with ICAM-1 expression level. The prognosis of patients with ICAM-1-negative tumors was poorer than the prognosis of those with ICAM-1-positive tumors.CONCLUSIONS: These findings suggest that ICAM-1 expression on cancer cells is closely associated with lymph node metastasis in gastric cancer, under the influence of the host immunosurveillance system.