What is the thyroid?

The thyroid gland is a small, butterfly-shaped gland located in the neck, below the Adam's apple. The thyroid gland produces the hormones thyroxine (also called T4) and triiodothyronine (also called T3). These hormones play a role in certain bodily functions, including body temperature, mood and excitability, pulse rate, digestion, and others.

What is thyroid cancer?

Sometimes thyroid tissue begins to grow uncontrollably, which can cause one or more nodules (growths) to form in the thyroid. The reason why this happens is unknown. Cancer is the biggest worry when nodules form. Cancerous nodules can invade the tissues of the neck, spread to the surrounding lymph nodes, or to the bloodstream, and then to other parts of the body.

There are four types of thyroid cancer:

  • Papillary: This is the most common type: more than 70 percent of thyroid cancers are papillary. This cancer usually does not grow very fast and does not spread quickly into surrounding tissue.
  • Follicular: This type makes up 10 to 15 percent of thyroid cancers. Follicular cancer can travel through the bloodstream and into other areas of the body, such as the lungs or bone.
  • Medullary: This type accounts for 4 percent of thyroid cancers. It is more likely to develop if there is a family history (others in the family have it) of this type of cancer.
  • Anaplastic: This type is rare (about 2 percent of thyroid cancers). Anaplastic cancer is a fast-growing cancer, spreading quickly into surrounding tissue. Treatment is the least effective in this type of cancer.

What are the risk factors for thyroid cancer?

  • Gender: Women are about three times more likely than men to develop thyroid cancer.
  • Age: In women, thyroid cancer is usually diagnosed in their 40s and 50s. Men are usually diagnosed in their 60s and 70s.
  • Family history (genetics): Thyroid cancer can sometimes run in families. Inheriting an abnormal gene can increase the risk of developing medullary thyroid cancer.
  • Exposure to radiation: Radiation treatments to the head and neck, especially treatments during childhood, can lead to thyroid cancer. Exposure to radiation can also come from fallout from a nuclear power plant accident. Tests that use radiation to make a medical diagnosis – such as dental X-rays or mammograms – do not cause thyroid cancer.
  • History of goiter: Goiter is an enlargement (growth) of the thyroid gland.
  • Lack of iodine: Iodine is necessary to produce thyroid hormone. Thyroid cancer is more common in parts of the world where there is a lack of iodine in the diet, such as central Asia and central Africa. In the United States, iodine is present in table salt and other foods, which lowers the risk of thyroid cancer.

What are the symptoms of thyroid cancer?

In most cases, there are no signs or symptoms in the early stages of thyroid cancer. Having one or more of the following symptoms does not necessarily mean that you have thyroid cancer; other conditions can cause these symptoms. However, one or more of these symptoms might occur as thyroid cancer grows:

  • Lump in the neck
  • Pain in the lower front part of the neck
  • Trouble breathing
  • Trouble swallowing
  • Hoarseness
  • Swollen lymph nodes, especially in the neck

How is thyroid cancer diagnosed?

One or more of the following tests help to diagnose thyroid cancer:

  • Physical exam: A physical exam can check for lumps or swelling in the neck, enlargement of the thyroid (goiter), and general health.
  • Blood tests: Blood tests check for levels of hormones released by other organs in the body.
  • Thyroid scan: A special camera and radioactive iodine (given as a pill) produce an image of the thyroid on a computer screen. This test is not ordered very often since it is only useful in certain cases.
  • Other scans/imaging tests (CT scan, radioiodine scan, PET scan, MRI): These tests use various methods to determine where the thyroid cancer is, how large it is, and how far it has spread.
  • Fine-needle aspiration (FNA) biopsy: During this procedure, a thin needle is inserted through the skin and into the thyroid gland and/or nodules. A sample of cells is removed and checked for cancer.
  • Ultrasound of the thyroid: This test determines the size of the lump on the thyroid. It is also used to guide a FNA biopsy.
  • Surgical biopsy: Since individual nodules cannot be removed, surgery is done to take out either one thyroid lobe (one side) or the whole thyroid.
  • Genetic testing: A genetic test is a blood test that looks at a person’s DNA, or genetic information.

How is thyroid cancer treated?

The term “stage” is used to describe the size of a tumor, how far it has spread within the thyroid gland, or how much the cancer has spread to other areas of the body.

The stages are 0 through IV: the lower the stage, the less the cancer has spread. Treatment is based on the stage and the type of cancer.

These are the ways thyroid cancer is treated:

  • Radioactive iodine: This is the most commonly used treatment. Uses high doses of radioactive iodine given orally (by mouth). The radioactive iodine collects in any remaining thyroid tissue and cancer cells that have spread throughout the body. This treatment kills the cancer cells without harming healthy tissue.
  • Radiation therapy: Used very rarely. Uses X-rays or other types of radiation to kill cancer cells or prevent cancer from spreading. External-beam radiation uses a machine to send radiation to the area where cancer is spreading. Radiation can also be given internally (into the body) through needles, catheters, and other methods.
  • Chemotherapy: Uses drugs to kill cancer cells or prevent cancer from spreading.
  • Hormone therapy: Drugs are used to block the release of certain hormones that can cause cancer to spread or recur (come back).
  • Clinical trials: These are studies of experimental therapies to gather information. Patients take part in these trials to help determine if new treatments are safer and more effective than the current treatments.

What are the survival rates for people with thyroid cancer?

The most common types of thyroid cancer can often be completely removed with surgery. These are the survival rates:

  • The 5-year survival rates for people with papillary and follicular thyroid cancers are greater than 90 percent.
  • The 5-year survival rate for people with medullary thyroid cancer is about 86 percent; the 10-year survival rate is about 65 percent.
  • The 5-year survival rate for people with anaplastic thyroid cancer is about 7 percent.

Can thyroid cancer be prevented?

In many cases, it is not possible to prevent thyroid cancer. However, the following might help reduce or eliminate the risk of thyroid cancer:

  • Having prophylactic (preventive) surgery: Changes in certain genes can cause an increased risk of thyroid cancer. A person might choose to have his or her thyroid removed to prevent cancer from developing there.
  • Eating a healthy diet. A diet high in fruits and vegetables and low in animal fat can reduce the risk of many types of cancer. The American Cancer Society recommends eating at least five servings of fruits and vegetables every day. Unsaturated fats (omega-3 fatty acids), especially those found in salmon and other fish, might help protect against cancer. Maintaining a healthy weight can also help protect against many diseases, including cancer of the thyroid.


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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 8/31/2015...#12210