Biomolecular Markers for Improving Management of Follicular and Medullary Thyroid Cancer

Abstract

Thyroid cancer usually presents as a thyroid nodule. According to different reports, more than 95% of thyroid nodules are benign. The gold standard for preoperative diagnosis of thyroid cancer is fine-needle aspiration cytology (FNAC). Especially in diagnosing medullary thyroid carcinoma (MTC) and some cases of well-differentiated thyroid carcinomas, biomolecular markers are proposed to increase the diagnostic value of FNAC. In this chapter, we mainly focused on classification, genetics, use of biomolecular and invasive markers, as well as treatment of follicular thyroid cancer (FTC) and MTC. In the case of FTC, some molecular and immunohistochemical markers are proposed and are currently under investigation principally for improving preoperative diagnosis. Unlike MTC, there is no powerful biomarker such as calcitonin (Ct) for FTC diagnosis. In the follow-up, serum thyroglobulin (Tg) and whole-body iodine-131 scintigraphy are effective. MTC has relatively poor prognosis. Postsurgical therapy is scarcely effective. Blood Ct is the best studied and preferred marker in the diagnosis and follow-up of MTC. It can be measured in the basal state or after provocative stimuli such as pentagastrin and high-dose calcium. Carcinoembryonic antigen (CEA) and chromogranin A (CgA) are the other markers currently used for selected cases. Ct and CEA doubling times are gaining importance for the prognosis of MTC. The importance of rearranged during transfection (RET) proto-oncogene screening in MTC is also discussed in this chapter. RET has also become a therapeutic target. In conclusion, the management of FTC and MTC includes diagnostic and therapeutic problems. However, thanks to the development of translational medicine, the biomolecular marker studies are improving FTC and MTC diagnosis, prognosis, and therapy.