['Several studies have revealed a correlation between sialosyl Tn antigen (STN) and certain clinicopathologic features of various cancers, and that STN is an independent prognostic factor. However, the clinical significance of the expression of STN in gastric cancer has not been reported. Thus, the purpose of this study was to evaluate immunohistochemically the clinical significance of expression of STN in gastric cancer.', 'The expression of STN in surgically resected specimens of human gastric cancer was evaluated immunohistochemically using a monoclonal antibody (TKH-2), in 60 patients whose serum STN levels were measured and in 54 patients with advanced cancer who had been followed for more than 5 years after gastrectomy. The correlations between the level of STN expression and clinicopathologic factors were analyzed. The staining intensity was graded as follows: (-), less than 5% of the cancer cells expressed STN; (+), 5-50%; (++), more than 50%.', 'Sialosyl TN antigen staining was detected mainly on the cell membrane, in the cytoplasm, and in the luminal contents, and 57.2% of the 60 specimens expressed STN, whereas the corresponding value for positive serum levels was 15%. A higher percentage of advanced tumors expressed STN than did the early cases, but the difference was not statistically significant. All cases with strong staining, the (++) cases, were advanced cases either with lymph node metastases or with cancer invading in or beyond the muscle layer proper. The expression of STN appeared to be related to the clinical stage, the extent of cancer invasion, and the presence of lymph node metastases. Sialosyl TN antigen was detected in the serum in less than 6% of the patients whose tumors were (-) or (+) for STN expression, and in 86.7% of the patients whose tumors expressed high levels of STN (++). The estimated 5-year survival in advanced cases (Stage III) was significantly better in those with negative STN expression than in those with positive STN expression (P < 0.01).'] Is sialosyl Tn antigen expression associated with the prognosis of patients with advanced gastric cancer?