Expression of epithelial-mesenchymal transition regulators TWIST, SLUG and SNAIL in follicular thyroid tumours may relate to widely invasive, poorly differentiated and distant metastasis

Aims To assess the expression of epithelial-mesenchymal transition (EMT) regulators in follicular thyroid tumours. Methods and results The expression of E-cadherin (E-CAD) and transcription factors TWIST, SLUG and SNAIL in follicular thyroid tumours was examined by immunohistochemistry in tissue samples, including 18 follicular adenomas (FA), 12 minimally invasive follicular thyroid carcinomas (MI-FTC), 16 widely invasive follicular thyroid carcinomas (WI-FTC), 10 poorly differentiated follicular thyroid carcinomas (PDTC) and six anaplastic thyroid carcinomas (ATC). Metastatic tumour tissues from six of these cases were also examined. The results showed an increasing expression trend of EMT regulators in a panel of follicular tumour cases with a spectrum of morphological subtypes from low- to high-risk malignancy. The expression of EMT regulators was higher in the WI-FTC, PDTC and ATC groups but focal and lower in the FA and MI-FTC groups. Different expression intensity of E-CAD and EMT regulators at the tumour centre part and the invasive front (IF) was observed. The loss of E-CAD and expression of EMT regulators was significantly correlated with distant metastasis and vascular invasion (VI) in the well-differentiated follicular carcinoma (WD-FTC), and six tumours of metastatic sites also showed variables positive for EMT regulators. The disease-free survival analysis showed an apparent relationship between the expression of EMT regulators and the tumour disease-free outcomes in WD-FTC. Conclusions Our study supported the role of EMT in the development of follicular thyroid carcinoma and indicated that EMT regulatory proteins may play an important role in WD-FTC that are widely invasive and exhibit distant metastasis.