Carcinoembryonic antigen and nonspecific cross-reacting antigen in thyroid cancer. An immunocytochemical study using polyclonal and monoclonal antibodies.

The expression of carcinoembryonic antigen (CEA) and related antigens in formalin-fixed paraffin-embedded tissues of 200 primary thyroid carcinomas and 22 nonmalignant thyroid lesions was studied immunocytochemically by using three monoclonal antibodies recognizing different epitopes on CEA and related antigens. The monoclonal antibody 431/31 defined epitope (present only on CEA) was found exclusively on 77% of the medullary thyroid carcinomas and on 100% of hyperplastic C-cell nodules adjacent to infiltrating C-cell carcinomas. The monoclonal antibodies 374/14 and 250/183, defining epitopes present on CEA and the nonspecific cross-reacting antigens 95 or 55, reacted with 88% and 82%, respectively, of the medullary carcinomas, but labelled also many nonmedullary thyroid carcinomas (follicular 34% and 18%, papillary 42% and 30%, anaplastic 18% and 13%), follicular adenomas, and nonneoplastic follicle-cell lesions. Similar results were obtained by using a polyclonal CEA antiserum preabsorbed with lyophilized spleen tissue. The findings suggest that nonspecific cross-reacting antigens can be expressed by all types of thyroid carcinoma, while CEA is present only in C-cell tumors of this organ.