The thyroid gland sits in the front of the neck just below the voice box (larynx). It is made up of 2 main lobes (right and left) joined across the middle by a thinner strip called the isthmus. There is also a much smaller pyramidal lobe in some people. The gland is butterfly or bow tie shaped.
It produces thyroid hormones called thyroxine (T4) and tri-iodothyronine (T3). These hormones are very important and help control the body’s metabolism (use of energy). The thyroid gland also produces calcitonin. This helps control the amounts of calcium and phosphate salts in the body. The level of calcitonin is raised when medullary thyroid cancer is present.
Compared to breast, lung, prostate and bowel cancers thyroid cancer is much less common. In 2010, there were approximately 2654 new cases (1906 women, 748 men) diagnosed in the UK.
(Compared to breast cancer 49,961: lung cancer 42,026: bowel cancer 40,695: prostate cancer 40,975. For more information go to UK Cancer Research Stats.)
Thyroid cancer, the most common endocrine-related cancer, presents as a lump (nodule) in the thyroid and usually does not cause any symptoms. Rarely, thyroid cancer may cause pain, difficulty swallowing, or hoarseness.
Papillary thyroid cancer is the most common type of thyroid cancer (70% to 80% of thyroid cancers) and can occur at any age. Follicular thyroid cancer (10% to 15% of thyroid cancers) tends to occur in somewhat older patients than does papillary cancer. Medullary thyroid cancer (5% to 10% of thyroid cancers) is more likely to run in families and may be diagnosed by genetic testing. Anaplastic thyroid cancer (less then 2% of thyroid cancers) is the least likely to respond to treatment.
Thyroid cancer is more common in people who have a history of exposure of the thyroid gland to radiation or a family history of thyroid cancer. Also, thyroid cancer is more common as we get older. In most patients, we do not know why thyroid cancer forms.
A diagnosis of thyroid cancer is typically made on the basis of a needle biopsy of a thyroid nodule or is confirmed by testing after the nodule is removed during surgery. Although thyroid nodules are very common, less than 1 in 10 contain a thyroid cancer.
The primary therapy for patients with thyroid cancer is surgery, followed by thyroid hormone therapy for the rest of their life. Radioactive iodine may be used to destroy any remaining thyroid cells, both normal and cancerous, after removal of the thyroid gland by surgery.
Thyroid swellings/nodules are very common but most nodules are not cancers.
Usually it is not known why a particular person has developed thyroid cancer but there are some known risk factors. These include:
- Previous exposure to radiation (for example children in Russia exposed to radiation from the Chernobyl accident, patients who may have had radiotherapy (x ray treatment) for a different type of cancer as a child or young adult)
- Family history of thyroid cancer (particularly important for medullary thyroid cancer)