Expression of cytokeratins and vimentin in epithelial cells of normal and pathologic thyroid tissue

The presence of intermediate filament proteins of the cytokeratin and vimentin type was evaluated in normal and pathologically changed thyroid tissue specimens. Using the indirect immunoperoxidase technique with 4 different cytokeratin monoclonal antibodies: RCK114 (broad spectred), K2080 (broad spectred), RGE53 (directed against component 18, present in simple epithelium) and RKSE60 (directed against component 10, associated with keratinization). Co-expression of cytokeratin and vimentin was evaluated with a double immunoenzyme staining technique. The results indicate that normal and transformed cells express cytokeratins of the non-epidermal type. Cytokeratins of the epidermal type are sometimes present in carcinomas. They do not differentiate in tumour type (i.e. papillary, follicular, anaplastic or medullary carcinoma). The co-expression of cytokeratins and vimentin is not restricted to carcinomas: in a small percentage of cases it is also present in normal epithelial cells of the thyroid gland. Moreover, the distribution pattern of cytokeratins and vimentin within the cell is changed in malignant transformed epithelial cells of the gland and seems to be inversely related to the degree of differentiation of these cells. The implications of our findings for the possible use of cytokeratins and vimentin in diagnostic pathology are discussed.