Follicular thyroid carcinoma (FTC) is a malignant form of thyroid tumor that originates in the follicular cells of the thyroid. This form of thyroid carcinoma is considered the second most common thyroid cancer, with the frequency of approximately 15% of all thyroid cancers, after papillary thyroid carcinoma. The exact cause of thyroid cancers including FTC is unknown; however, thyroid cancers are found more often in patients with previous history of exposure to external radiation as well as in those with family history of thyroid diseases. Usually, FTC occurs in individuals of ages between 15 and 84 years, and it is less common in children. FTC may invade neighbor tissues and spread easily to other organs. Vascular invasion is a distinguishing feature for FTC, therefore, distant metastases are common. Noticeably, about 10-15% of patients with FTC have lung and bone metastases. Involvement of lymph nodes in FTC is less common in FTC (8-13%) than in some other thyroid cancers.
Mortality depends mainly upon the degree of vascular invasion with a rate of 1.5% in females and 1.4% in males. However, FTC and almost all thyroid cancers are curable. Caucasians and women are more affected with FTC than Blacks and men, respectively. Relative incidence of follicular carcinoma is higher in areas of endemic goiter.