An anti-sTn monoclonal antibody 3P9 was generated in our laboratory by immunization of mice with human colon adenocarcinoma cell line SW1116.To estimate its potential use as tumor marker, we studied the expression pattern of 3P9 by immunohistochemistry and analyzed the significant difference of positive rate in a variety of carcinomas and normal tissues.We found 3P9 can significantly identify the adenocarcinoma endometrium, but there was no significant correlation between the expression pattern and tumor differentiation.However, in terms of high specificity and sensitivity, 3P9 may be an in vitro diagnostic marker of adenocarcinoma endometrium immunohistochemicaily.