Cytokeratin expression profiles in thyroid carcinomas.

The aim of this study was to establish the cytokeratin expression profile of different types of thyroid carcinoma. The expression of cytokeratins (CKs) 1, 4, 6, 7, 10/13, 18, 19 and 20 in 153 thyroid carcinomas were examined by immunohistochemistry. All papillary carcinomas (n=86) and follicular carcinomas (n=19) showed expression of CK7 and CK18. The staining was often diffuse. CK19 staining was expressed in all papillary carcinomas and the staining was often diffuse. The staining was noted in 68% of follicular carcinomas and the staining was often focal. No difference in the expression was noted between the minimally invasive and widely invasive follicular carcinomas. Poorly differentiated carcinomas (n=10) showed CK7, CK18, CK19 expression in 60%, 60% and 40%, respectively. Anaplastic carcinomas (n=25) expressed CK7 in 84%, CK18 in 80%, CK19 in 76% and CK10/13 in 16%. Medullary carcinomas (n=13) showed CK7 expression in 100%, CK18 in 85% and CK19 in 77%. None of the medullary carcinomas showed diffuse positivity to CK19. All the thyroid carcinomas were negative for CKs 1, 4, 6 and 20. Cytokeratin expression profile for each type of thyroid carcinoma was established.