An optical and ultrastructural study of the localization of carcinoembryonic antigen (CEA) in normal and cancerous human rectocolonic mucosa.

An immunoenzymologic method using peroxidase-labeled antibodies has been applied for the localization of carcinoembryonic antigen (CEA) on frozen sections, on Araldite-embedded sections, and on isolated cell preparations of normal rectocolonic mucosa and of rectal and colonic cancers (adenocarcinomas and one villous tumor). CEA appears as a component intimately associated with the external coating of the striated border of the normal columnar cell and with the external coating of the apical pole of the cancerous cell. CEA is also found as an intracellular component of the normal epithelial cell of the rectocolonic mucosa, mainly the goblet cell. In tumors, it appears as an intracellular component of the mucussecreting cell. Its presence in the cell coat and interior of the cell correlates with the degree of differentiation of the cells, whether cancerous or not. Progressive accumulation of CEA in the normal colonic epithelial cell has been observed in cells undergoing maturation. Its release by the mature goblet cell has also been observed. These results confirm that CEA is a normal glycoprotein constituent of the epithelial cell of the human adult rectocolonic mucosa, synthesized and discharged by this cell. The difference in CEA content, already reported, between the cancerous and the normal rectocolonic mucosa appears quantitative and not qualitative.