Thyroid cancer starts in the cells that make up your thyroid gland— one of several glands that make up your endocrine system. Shaped like a butterfly, with a right lobe and a left lobe, the thyroid gland is located at the base of the throat near the trachea (windpipe). While thyroid cancer can occur in any age group, it is most common after age 30.
Types of Thyroid Cancer
There are five main types of thyroid cancer. Each is classified based on how similar they look to normal thyroid cells under a microscope and by the type of cell from which they develop.
- Papillary thyroid cancer. This is the most common type of thyroid cancer, accounting for about 80% of all thyroid cancer cases in the United States. It begins in follicular cells and grows slowly. In most cases, it is usually found in only one lobe. If diagnosed early, most people with papillary thyroid cancer can be cured. Papillary thyroid cancer is a differentiated thyroid cancer, meaning that the tumor looks similar to normal thyroid tissue under a microscope
- Follicular thyroid cancer. Follicular thyroid is also a differentiated thyroid cancer, however, it is less common than papillary thyroid cancer, making up about 15% of all thyroid cancers. It begins in follicular cells and grows slowly. If diagnosed early, most people with follicular thyroid cancer can be treated successfully.
- Hurthle cell cancer. Also called Hurthle cell carcinoma, hurthle cell cancer arises from a certain type of follicular cell. While Hurthle cell cancer is very rare, it can be more aggressive than other types of thyroid cancer.
- Medullary thyroid carcinoma (MTC). MTC makes up about 3% of all thyroid cancers. It develops from C cells in the thyroid gland, and is more aggressive and less differentiated than papillary or follicular cancers. It is sometimes the result of a genetic syndrome called multiple endocrine neoplasia type 2 (MEN2). About 25% of all MTC is familial, meaning that your family members will have a possibility of a similar diagnosis. Certain tests can confirm familial medullary thyroid cancer (FMTC).
- Anaplastic thyroid cancer. This type is rare, accounting for about 1% of all thyroid cancers. It tends to grow and spread very quickly, making it difficult to treat successfully.