Hashimoto's thyroiditis: Is the epithelium premalignant?

This paper will review the pathologic definition of chronic lymphocytic thyroiditis, its relationships and epidemiology, and its association with thyroid neoplasms. The epithelium of thyroid glands affected by lymphocytic thyroiditis has been studied by various techniques. Immunohistochemical markers, oncogene changes and genetic mutations that are shared by the thyroiditic epithelium and papillary thyroid carcinoma will be reviewed. Morphologic similarities of the follicular epithelium in thyroiditis and in papillary carcinoma, similar immunohistochemical reactions with markers such as cytokeratin 19, HBME-1 and Galectin-3 and results of ret/PTC oncogene, mutational and loss of heterozygosity studies have raised questions about the nature of the thyroiditic epithelium and whether it is neoplastic or dysplastic. The results of work done in our laboratory in these areas will be compared and contrasted with work cited in the literature. This information will be assessed in terms of its clinical implications to everyday practice.