Carcinoembryonic antigen (CEA) expression in early embryogenesis: a study of the first trimester of gestation.

The immunohistological CEA positivity was studied in 711 tissue samples derived from the ecto-, meso- and entoderm of 63 embryos obtained during the first 12 weeks of gestation. It was found that CEA was expressed by derivates of all three germ layers, although the strongest reactions and the highest incidence of positivity was found in organs derived from the entoderm. In the 7th week of gestation the antigen was first seen in mesodermal and entodermal tissues; only after the 8th week the first appearance of CEA was noted, though only in 2/9 ectodermal organs examined. It therefore seems that the initially described high preponderance of CEA positivity of entodermal organs, previously observed for later stages of gestation, can be confirmed. However, not only are exceptions seen in organs of this germ layer, but CEA can also be expressed in tissues of the two other germ layers early in ontogenesis.