Infiltration of dendritic cells in relation to tumor invasion and lymph node metastasis in human gastric cancer. The infiltration of dendritic cells determined in 210 patients with gastric carcinoma was investigated from the standpoint of tumor invasion, lymph node metastasis, and prognosis. Dendritic cell infiltration was graded as "slight" and "marked." The 39% frequency in the marked infiltration group at the mucosal stage did not change in proportion to invasion into the deeper layers. The 5-year survival rate was 60.4% in patients with marked infiltration and 38.8% in those with slight infiltration, which was statistically different (P less than 0.01). The difference in survival rates was only statistically significant in those with cancer emerging from the serosa (P less than 0.001). There was a similar incidence of lymph node metastasis between the marked and slight infiltration groups in each grade of tumor invasion. However, marked infiltration of dendritic cells prevented widespread nodal involvement beyond the primary node in cases of advanced carcinoma (P less than 0.05). These findings indicate that infiltrating dendritic cells do not prevent the spread of tumor invasion but do prevent nodal involvement; therefore, for patients with a gastric cancer emerging from the serosa, the prognosis will be good. 