Carcinoembryonic antigen (CEA) expression and heterogeneity in primary and autologous metastatic gastric tumours demonstrated by a monoclonal antibody.

The expression of carcinoembryonic antigen (CEA) in gastric malignancies has been assessed using a monoclonal antibody in an immunoperoxidase technique. Of 119 primary tumours examined, 92% reacted with the antibody. Metastases were available for 81 of the patients and 83% were CEA positive. A noteworthy observation was the detection of malignant cells in the lymph nodes of two patients, as a result of the presence of CEA, who were originally reported to be free of metastases. Of those patients whose primary tumours expressed CEA, 86% had at least one CEA positive metastasis. Two or more metastases were available from 60 of the patients and in 20% the secondaries were a mixture of positive and negative for CEA. Consequently, the CEA status of a single lesion does not enable confident prediction of expression in other metastases. In addition to variation between multiple lesions removed from the same patient phenotypic diversity of expression was observed between tumour cells of a given mass. Such distribution of the CEA detected by this monoclonal antibody may impose certain restrictions on its application. However, the high frequency of expression by gastric cancers indicate that it is a potentially useful antigen as a target for radiolocalisation or therapeutic agents.