Immunohistochemical observations of carcinoembryonic antigen (CEA) and CEA-related substances in normal and neoplastic pancreas. Pitfalls and caveats in CEA immunohistochemistry.

Carcinoembryonic antigen (CEA) and its related substances in normal and neoplastic pancreas were studied by the indirect immunoperoxidase method, using six conventional and monoclonal antibodies. Gastric and colonic tissues were used as positive controls. The antigenicity of CEA and CEA-related substances were more unstable than expected. Normal gastric and colonic epithelial cells were unequivocally positive for the antigens in frozen sections, but their staining intensity weakened in paraffin sections. In normal pancreatic ducts, there was nonspecific cross-reacting antigen (NCA) or CEA-related substances containing antigenic determinants common to NCA, which were observed more easily in frozen sections than in paraffin sections. CEA or CEA-related substances lacking NCA-like determinants were not detected in normal pancreas. In all pancreatic adenocarcinomas, CEA or CEA-related substances with or without NCA-like determinants were demonstrated. CEA immunohistochemistry with different monoclonal antibodies might be useful to overcome the heterogenous specificities of conventional anti-CEA antibodies.