Genetic Alterations in Follicular Cell-derived Thyroid Carcinomas

The molecular approaches to human diseases are receiving greater attention following the completion of the Human Genome Project. Molecular biology techniques are being widely applied to the field of tumor biology, and thyroid carcinomas are not an exception; several genetic alterations have been suggested to play roles in thyroid carcinogenesis and its progression. Malignant tumors arising from thyroid follicular cells can be classified into papillary carcinoma, follicular carcinoma, poorly differentiated carcinoma and anaplastic carcinoma. BRAF mutation, RET/PTC rearrangement and RAS mutation are the suggested molecular causes of papillary thyroid carcinoma (PTC). RAS mutation, PAX8- PPARγ rearrangement, PTEN mutation or methylation, and PIK3CA mutation are known to induce follicular thyroid carcinoma (FTC). Poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC) are related to adding p53 or β-catenin gene alterations to those of papillary or follicular carcinomas. The more aggressive genetic alterations are added stepwise as thyroid tumors advance from differentiated PTC or FTC to less differentiated PDTC and finally to ATC. Studying the molecular mechanisms underlying thyroid carcinogenesis may help overcome the limitations of the current diagnostic methods and this may provide more accurate diagnostic and prognostic tools. Furthermore, research at the molecular level is essential for personalized therapies and creating targeted therapies for thyroid carcinomas.