Classically, TGFβ signaling is a tumor suppressor in normal epithelial cells (e.g., thyrocytes), as it exerts an antimitogenic effect; nevertheless, the cumulative evidence shows that it plays additional roles in thyroid-cell differentiation and in the epithelial-to-mesenchymal transition (EMT) process, and promotes malignant progression of cancer. Here, TGFB1 is linked to cancer.