The peptide core of stomach mucin M1, which was recentlyshown to be Mucin 5AC, is recognised by this MAb. The C-terminal cysteine-rich region of the MUC5AC peptide corecontains its epitope. Beta-mercaptoethanol destroys itsepitope, while periodate therapy does not. This mucinexhibits the reverse expression pattern of MUC2 since it isfound in primary ovarian mucinous malignancy but istypically missing in colorectal adenocarcinoma. Anti-MUC5AC may help distinguish primary mucinous ovariantumours from colon adenocarcinoma that has spread tothe ovary when used in conjunction with a panel ofantibodies. In addition, MUC5AC antibodies may be helpfulin identifying intestinal metaplasia, pancreatic carcinoma,and precancerous alterations in comparison to normalpancreas.