Objective: To explore the expression of thyroid transcription factor-1 (TTF-1) in thyroid tumors and in different parts of follicular epithelium and the correlation of expression of TTF-1 with the expression of RET, galectin-3 (Gal-3) and mucin-1 (MUC1) genes.
Methods: One hundred thirty-three samples of resected thyroid tumors were examined by streptavidin/peroxidase (S-P) immunohistochemical technique to detect the expression of TTF-1 and RET, Gal-3, and MUC1 genes.
Results: (1) TTF-1 was expressed in the nuclei and cytoplasm of different kinds of tumor cells and normal cells around the tumors. There was no significant difference between the expression of TTF-1 in nuclei of malignant thyroid tumor cells and that in nuclei of benign thyroid tumor cells (P > 0.05). The positive expression rate of TTF-1 was 27.40% in cytoplasm of benign tumor and was 66.10% in cytoplasm of malignant tumor was 66.10% (P < 0.05). (2) The expression rate of RET gene was 38.9% in thyroid adenoma, 88.4% in papillary carcinoma, and 87.5% in follicular carcinoma. The difference of expression rate of RET gene between adenoma and both of papillary and follicular carcinomas was statistically significant (P < 0.05). (3) The expression rate of MUC1 was 23.3% in benign tumor and 50.9% in malignant tumor. The expression rate of MUC1 was lower in benign thyroid diseases (nodular goiter and adenoma) than in thyroid papillary carcinoma and follicular carcinoma (P < 0.05). (4) The expression rate of Gal-3 gene was 38.4% in benign tumor and 88.1% in malignant tumor. (5) The expression rates of Gal-3 and MUC1 in benign lesions (nodular goiter and adenoma) were lower than those in thyroid papillary and follicular carcinomas (P < 0.05). The expression of Gal-3 and that of MUC1 in thyroid carcinomas were fundamentally parallel. However, the sensitivity of Gal-3 was higher than that of MUC1. In part of adenomas Gal-1 and MUC1 were positive locally simultaneously. The expression of TTF-1 in cytoplasm was associated with that of Gal-3 and MUC1.
Conclusion: The expression of TTF-1 in nucleus is a phenomenon common to both normal and pathological thyroid follicles. Combined tests of RET, Gal-3 and MUC1 may act as the diagnostic markers to distinguish benign follicular tumor from malignant ones. Expression of TTF-1 in cytoplasm is probably a characteristic of malignant phenotypes of thyroid tumors.