CEA and non-specific cross-reacting antigen (NCA) in medullary carcinomas of the thyroid.

An immunohistological study of five cases of medullary carcinoma of the thyroid was undertaken with monospecific antisera against CEA and NCA. CEA was present in different areas of the tumors: cell cytoplasm, cell membrane at its apical pole when the tumor had a pseudoglandular organization, deposits in the lumen of pseudoglands, and peri- and extra-cellular deposits. From these extra-cellular deposits, CEA could easily reach the circulation, thus causing rising serum levels up to high values. NCA was found in the same tumors and in the same localizations.