Thyroid cancer occurs in the cells of the thyroid — a butterfly-shaped gland located at the base of your neck, just below your Adam’s apple. Your thyroid produces hormones that regulate your heart rate, blood pressure, body temperature and weight.
Although thyroid cancer isn’t common in the United States, rates seem to be increasing. Doctors think this is because new technology is allowing them to find small thyroid cancers that may not have been found in the past.
Most cases of thyroid cancer can be cured with treatment.
Thyroid cancer typically doesn’t cause any signs or symptoms early in the disease. As thyroid cancer grows, it may cause:
- A lump that can be felt through the skin on your neck
- Changes to your voice, including increasing hoarseness
- Difficulty swallowing
- Pain in your neck and throat
- Swollen lymph nodes in your neck
When to see a doctor
If you experience any these signs or symptoms, make an appointment with your doctor. Thyroid cancer isn’t common, so your doctor may investigate other causes of your signs and symptoms first.
It’s not clear what causes thyroid cancer.
Thyroid cancer occurs when cells in your thyroid undergo genetic changes (mutations). The mutations allow the cells to grow and multiply rapidly. The cells also lose the ability to die, as normal cells would. The accumulating abnormal thyroid cells form a tumor. The abnormal cells can invade nearby tissue and can spread throughout the body.
Types of thyroid cancer
The type of thyroid cancer you have determines treatment and prognosis. Types of thyroid cancer include:
- Papillary thyroid cancer. The most common form of thyroid cancer, papillary cancer arises from follicular cells, which produce and store thyroid hormones. Papillary thyroid cancer can occur at any age, but most often it affects people ages 30-50.
- Follicular thyroid cancer. Follicular cancer also arises from the follicular cells of the thyroid. It usually affects people older than age 50. Hurthle cell cancer is a rare and potentially more aggressive type of follicular thyroid cancer.
- Medullary thyroid cancer. Medullary thyroid cancer begins in thyroid cells called C cells that produce the hormone calcitonin. Elevated levels of calcitonin in the blood can detect medullary thyroid cancer at a very early stage. Certain genetic syndromes increase the risk of medullary thyroid cancer, although this genetic link is uncommon.
- Anaplastic thyroid cancer. Anaplastic thyroid cancer is a rare and rapidly growing cancer that is very difficult to treat. Anaplastic thyroid cancer typically occurs in adults age 60 or older.
- Thyroid lymphoma. Thyroid lymphoma is a rare form of thyroid cancer that begins in the immune system cells in the thyroid and grows very quickly. Thyroid lymphoma typically occurs in older adults.
Factors that may increase the risk of thyroid cancer include:
- Female sex. Thyroid cancer occurs more often in women than in men.
- Exposure to high levels of radiation. Examples of high levels of radiation include those that come from radiation treatment to the head and neck and from fallout from such sources as nuclear power plant accidents or weapons testing.
- Certain inherited genetic syndromes. Genetic syndromes that increase the risk of thyroid cancer include familial medullary thyroid cancer, multiple endocrine neoplasia and familial adenomatous polyposis.
Thyroid cancer that comes back
Despite treatment, thyroid cancer can return, even if you’ve had your thyroid removed. This could happen if microscopic cancer cells spread beyond the thyroid before it’s removed. Thyroid cancer recurrence most often occurs in the first five years after surgery, but it can recur decades after your initial thyroid cancer treatment.
Thyroid cancer may recur in:
- Lymph nodes in the neck
- Small pieces of thyroid tissue left behind during surgery
- Other areas of the body
Thyroid cancer that recurs can be treated. Your doctor may recommend periodic blood tests or thyroid scans to check for signs of a thyroid cancer recurrence.
Tests and diagnosis
Tests and procedures used to diagnose thyroid cancer include:
- Physical exam. Your doctor will look for physical changes in your thyroid and ask about your risk factors, such as excessive exposure to radiation and a family history of thyroid tumors.
- Blood tests. Blood tests help determine if the thyroid gland is functioning normally.
- Removing a sample of thyroid tissue. During a fine-needle biopsy, your doctor inserts a long, thin needle through your skin and into the thyroid nodule. Ultrasound imaging is typically used to precisely guide the needle into the nodule.Your doctor uses the needle to remove samples of suspicious thyroid tissue. The sample is analyzed in the laboratory to look for cancer cells.
- Imaging tests. You may have one or more imaging tests to help your doctor determine whether your cancer has spread beyond the thyroid. Imaging tests may include computerized tomography (CT) scans, positron emission tomography (PET) or ultrasound.
- Genetic testing. Some people with medullary thyroid cancer may have genetic changes that can be associated with other endocrine cancers. Your family history may prompt your doctor to recommend genetic testing to look for genes that increase your risk of cancer.