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.
Thyroid cancer might not cause any symptoms at first. But as it grows, it can cause pain and swelling in your neck.
Thyroid cancer rates seem to be increasing.
Thyroid cancer typically doesn't cause any signs or symptoms early in the disease. As thyroid cancer grows, it may cause:
- A lump (nodule) 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
It's not clear what causes thyroid cancer but genetics play a role due to mutations.
The accumulating abnormal thyroid cells form a tumor. The abnormal cells can invade nearby tissue and can spread (metastasize) to other parts of the body.
Types of thyroid cancer
Thyroid cancer is classified into types based on the kinds of cells found in the tumor. Types of thyroid cancer include:
- Papillary thyroid cancer. The most common form of thyroid cancer, papillary thyroid cancer arises from follicular cells, which produce and store thyroid hormones. It often affects people ages 30 to 50.
- Follicular thyroid cancer. Follicular thyroid cancer also arises from the follicular cells of the thyroid. It usually affects people older than age 50.
- Anaplastic thyroid cancer. Anaplastic thyroid cancer is a rare type of thyroid cancer that begins in the follicular cells. It grows rapidly and typically occurs in adults age 60 and older.
- Medullary thyroid cancer. Medullary thyroid cancer begins in thyroid cells called C cells, which produce the hormone calcitonin. Elevated levels of calcitonin in the blood can indicate medullary thyroid cancer at a very early stage.
- Other rare types. Other very rare types of cancer of the thyroid are thyroid lymphoma, which begins in the immune system cells of the thyroid, and thyroid sarcoma, which begins in the connective tissue cells of the thyroid.
Factors that may increase the risk of thyroid cancer include:
- Female sex.
- Exposure to high levels of radiation. Radiation therapy treatments to the head and neck increase the risk of thyroid cancer.
- Certain inherited genetic syndromes. Such as familial medullary thyroid cancer, multiple endocrine neoplasia, Cowden's syndrome and familial adenomatous polyposis.
Thyroid cancer that comes back
Thyroid cancer may recur in:
- Lymph nodes in the neck
- Small pieces of thyroid tissue left behind during surgery
- Other areas of the body, such as the lungs and bones
Prevention for people with a high risk
Adults and children with an inherited gene mutation that increases the risk of medullary thyroid cancer may consider thyroid surgery to prevent cancer (prophylactic thyroidectomy).
Prevention for people near nuclear power plants
A medication that blocks the effects of radiation on the thyroid is sometimes provided to people living near nuclear power plants. The medication (potassium iodide) could be used in the unlikely event of a nuclear reactor accident. If you live within 10 miles of a nuclear power plant and are concerned about safety precautions, contact your state or local emergency management department for more information.
Tests and procedures used to diagnose thyroid cancer include:
- Physical exam.
- Blood tests.
- Ultrasound imaging. Ultrasound uses high-frequency sound waves to create pictures of body structures. To create an image of the thyroid, the ultrasound transducer is placed on your lower neck.
- Removing a sample of thyroid tissue. During a fine-needle aspiration 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.
- Other imaging tests. Imaging tests may include CT, MRI and nuclear imaging tests that use a radioactive form of iodine.
- Genetic testing.
Most thyroid cancers can be cured with treatment.
Treatment may not be needed right away
Very small thyroid cancers that have a low risk of spreading in the body might not need treatment right away. Instead, you might consider active surveillance with frequent monitoring of the cancer.
Most people with thyroid cancer undergo surgery to remove the thyroid. Operations used to treat thyroid cancer include:
- Removing all or most of the thyroid (thyroidectomy). An operation to remove the thyroid gland might involve removing all of the thyroid tissue (total thyroidectomy) or most of the thyroid tissue (near-total thyroidectomy). The surgeon often leaves small rims of thyroid tissue around the parathyroid glands to reduce the risk of damage to the parathyroid glands, which help regulate the calcium levels in your blood.
- Removing a portion of the thyroid (thyroid lobectomy). During a thyroid lobectomy, the surgeon removes half of the thyroid. It might be recommended if you have a slow-growing thyroid cancer in one part of the thyroid and no suspicious nodules in other areas of the thyroid.
- Removing lymph nodes in the neck (lymph node dissection). When removing your thyroid, the surgeon may also remove nearby lymph nodes in the neck. These can be tested for signs of cancer.
Thyroid surgery carries a risk of bleeding, infection, and nerve damage. Damage to your parathyroid glands also can occur during surgery, which can lead to low calcium levels in your body.
Thyroid hormone therapy
After thyroidectomy, you may take the thyroid hormone medication levothyroxine (Levoxyl, Synthroid, others) for life.
This medication has two benefits: It supplies the missing hormone your thyroid would normally produce, and it suppresses the production of thyroid-stimulating hormone (TSH) from your pituitary gland. High TSH levels could conceivably stimulate any remaining cancer cells to grow.
Radioactive iodine treatment uses large doses of a form of iodine that's radioactive.
Radioactive iodine treatment is often used after thyroidectomy to destroy any remaining healthy thyroid tissue, as well as microscopic areas of thyroid cancer that weren't removed during surgery. Radioactive iodine treatment may also be used to treat thyroid cancer that recurs after treatment or that spreads to other areas of the body.
Radioactive iodine treatment comes as a capsule or liquid that you swallow.
Side effects may include:
- Dry mouth
- Mouth pain
- Eye inflammation
- Altered sense of taste or smell
Most of the radioactive iodine leaves your body in your urine in the first few days after treatment.
External radiation therapy
Radiation therapy can also be given externally using a machine that aims high-energy beams, such as X-rays and protons, at precise points on your body (external beam radiation therapy). During treatment, you lie still on a table while a machine moves around you.
Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. Chemotherapy is typically given as an infusion through a vein. The chemicals travel throughout your body, killing quickly growing cells, including cancer cells.
Chemotherapy isn't commonly used in the treatment of thyroid cancer, but it's sometimes recommended for people with anaplastic thyroid cancer.
Targeted drug therapy
Targeted drug treatments focus on specific abnormalities present within cancer cells. By blocking these abnormalities, targeted drug treatments can cause cancer cells to die.
Injecting alcohol into cancers
Alcohol ablation involves injecting small thyroid cancers with alcohol using imaging such as ultrasound to ensure precise placement of the injection. This procedure causes thyroid cancers to shrink.