Papillary thyroid carcinoma cell lines TPC-1 (identified with RET mutation), BCPAP (identified with RET mutation) and K1 (identified with RET mutation) were exposed to different concentrations of TNF-α (0, 10 ng/mL, 20 ng/mL, 40 ng/mL) for 36 h, then extracted protein and mensurated the changes of classical epithelial mesenchymal transition (EMT) markers: E-cadherin, N-cadherin and vimentin. The gene discussed is RET; the disease is differentiated thyroid carcinoma.