Ultrastructural localization of carcinoembryonic antigen (CEA) on ultrathin cryosections of human tumours.

A new, more direct method for reliable localization of CEA on human tumours has been applied at the ultrastructural level. Freshly prepared biopsy material from breast and gastric tumours, as well as xenografted colon tumours from mice, and a colon tumour cell line (LS 174 T), were briefly fixed in glutaraldehyde and frozen in liquid propane. Ultrathin cryosections were labelled with monospecific CEA antibodies by applying gold-coupled second antibodies. Variations in the labelling patterns were found when comparing breast, colon, and gastric cancers. Apart from breast tumours, all other samples reveal significant extracellular CEA positivity on the cell membrane. Intracellular localization has been found on the endoplasmic reticulum, nuclear membrane, and, in breast tumours, on electron dense bodies. These investigations confirm our previous experimental results using preembedding labelling techniques before Epon inclusion.