Immunohistochemical study of the expression of S-100 protein, epithelial membrane antigen, cytokeratin and carcinoembryonic antigen in thyroid lesions.

The diagnosis of papillary carcinoma of the thyroid is based on the two morphological features that best characterize this tumor, the papillae and the nuclear changes. However, both the architectural and cytological hallmarks may be encountered in other conditions such as multinodular goiter, Grave's disease, thyroiditis and hyperplastic areas of follicular neoplasms and thus produce problems in the histopathological interpretation. The distinction of these lesions from papillary carcinoma has important implications for clinical management. Thus the availability of supportive diagnostic evidence would be helpful. In the present study we compared the immunoreactivity for S-100 protein, epithelial membrane antigen (EMA), cytokeratin (Ck) and carcynoembryonic antigen (CEA) in different thyroid pathologies. We conclude that the strong expression of S-100 protein, in combination with EMA expression, is of value in identifying papillary neoplasia and distinguishing it from papillary hyperplasia.