An immunohistochemical study of cytokeratin and vimentin in benign and malignant thyroid lesions.

Intermediate filaments in benign and malignant thyroid lesions were immunohistochemically studied using polyclonal and monoclonal anti-cytokeratin (CK), and monoclonal anti-vimentin antibodies. Antigenicity of CK and vimentin was almost completely destroyed during formalin fixation in normal thyroid and all thyroid lesions except for some cases of papillary and squamous cell carcinoma, although the latter showed negative immunostaining with anti-vimentin antibody. In sections fixed with Carnoy's fixative, most cases of papillary carcinoma showed an intense reaction product for polyclonal anti-CK, monoclonal anti-CK-7, CK-19 and anti-vimentin antibodies. The reaction product for anti-CK antibodies was located mainly in the apical cytoplasm and that for anti-vimentin antibody in the basal cytoplasm. However antigenicity was still destroyed by the fixative in many specimens of normal thyroid, benign thyroid lesions and follicular carcinoma. In frozen sections, all specimens showed preserved antigenicity for both antigens with an intense reaction product in papillary carcinoma, but this was weaker in normal thyroid, benign thyroid lesions and follicular carcinoma. Therefore, follicular cells under normal and pathological conditions contain intermediate filaments of CK and vimentin in their cytoplasm and co-expression of the antigens is significantly increased in papillary carcinoma.