Immunoexpression of HBME-1, high molecular weight cytokeratin, cytokeratin 19, thyroid transcription factor-1, and E-cadherin in thyroid carcinomas

To examine the immunohistochemical alterations associated with the histological dedifferentiation of thyroid carcinomas, we performed staining for HBME-1, high molecular weight cytokeratin (HCK), CK 19, thyroid transcription factor-1 (TTF-1) and E-cadherin (E-CD) on 125 various types of thyroid carcinomas. The HBME-1 staining was strong and diffuse in follicular carcinoma (FC), papillary carcinoma (PC), and poorly differentiated carcinoma (PDC), while it was rare in undifferentiated carcinoma (UC) as well as in benign lesions. Strong, diffuse staining for CK19 and HCK was predominantly found in PC, and these markers were not much found in other carcinomas. TTF-1 uniformly stained the tumor cells of all cases of PC, FC and Hurthle cell carcinoma (HC) and 42% of the PDC, while there was only focal staining in one case of the UC. Compared to the strong, diffuse reactivity in the benign lesions, E-CD staining was noted in 67% of PC, 80% of FC, 83% of HC, 58% of PDC and none of the UC. These results suggest that HBME-1 may be a marker for well-differentiated carcinomas while CK19 and HCK are phenotypic markers for papillary carcinoma. The loss or reduced expression of TTF-1 and E-CD may be markers for dedifferentiation.