Thyroid Cancer

Definition

Thyroid cancer is cancer of the thyroid gland. This gland makes thyroid hormone. It is found in the front of the neck. Thyroid gland tumors often appear as bumps in the neck, called nodules. In most cases, thyroid nodules are not cancerous. Those that are cancerous have the potential to spread throughout the body.

Thyroid Cancer

Thyroid tumor

© 2008 Nucleus Medical Art, Inc.

There are several types of thyroid cancer, including:

Papillary carcinoma—most common type

  • It usually grows very slowly, and often spreads to lymph nodes in the neck. If caught early, this type of thyroid cancer is often curable.

Follicular carcinoma—second most common type

  • It usually stays in the thyroid gland but can spread to other parts of the body, such as the lungs and bones. It does not usually spread to the lymph nodes. If caught early, this type of thyroid cancer is often curable.

Anaplastic carcinoma—rare form of thyroid cancer

  • It quickly invades the neck and other parts of the body, and is often fatal.

Medullary thyroid carcinoma (MTC)—cancer that develops from cells in the thyroid gland called C-cells

  • It often spreads to the lymph nodes, lungs, or liver before a thyroid nodule has been discovered. There are two types of MTC:
    • Sporadic MTC
    • Familial medullary thyroid carcinoma (FMTC)

Thyroid lymphoma—rare type of thyroid cancer

Causes

Unknown

Risk Factors

These factors increase your risk of developing thyroid cancer. Tell your doctor if you have any of these risk factors:

  • Diet low in iodine
  • History of radiation to the head, neck, or chest, especially in infancy or childhood
  • Family history of thyroid cancer
  • Sex: female
  • Age: 30 and over
  • Exposure to radioactive fallout (seen in patients exposed to radiation from nuclear accidents in Europe or as a result of being near nuclear testing during childhood)

Symptoms

If you have any of these symptoms do not assume it is due to thyroid cancer. These symptoms may be caused by other conditions. Tell your doctor if you have any of these:

  • A lump in the neck
  • Neck pain, sometimes going up to the ears
  • Hoarseness
  • Difficulty swallowing
  • Difficulty breathing
  • Persistent cough
  • Enlarged lymph glands in the neck

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam. This may include a careful examination of your neck to look for lumps or abnormalities.

Tests:

  • Fine needle aspiration—removal of fluid and cells from a thyroid nodule with the use of a very thin needle
    • This test can be done in the doctor's office and may or may not require a local anesthetic.
  • Blood test
  • Thyroid scan—x-rays taken after radioactive iodine is injected into the blood
    • The iodine is absorbed by the thyroid gland. This causes it to light up and be more visible on x-ray.
  • Ultrasound—a test that uses sound waves to examine thyroid nodules
  • Surgical biopsy—removal of a sample of thyroid tissue to test for cancer cells

Treatment

Once thyroid cancer is found, staging tests (possibly including CT scans and PET scans) are done to find out if the cancer has spread. Treatment depends on the stage of the cancer.

Depending on how much of the thyroid gland is removed, you may need to take thyroid hormone pills after surgery.

Radioactive Iodine Therapy

This uses large doses of radioactive iodine to destroy the thyroid gland and thyroid cancer without affecting the rest of the body. This treatment is used to destroy thyroid tissue not removed by surgery and to treat thyroid cancer that has spread to lymph nodes and other parts of the body.

This is the use of radiation to kill cancer cells and shrink tumors. Radiation is directed at the tumor from a source outside the body.

This is the use of drugs to kill cancer cells. Chemotherapy may be given in many forms including: pill, injection, and via a catheter. The drugs enter the bloodstream and travel through the body killing mostly cancer cells, but also some healthy cells. Chemotherapy to treat thyroid cancer is still investigational. Chemotherapy has not been shown to effectively control or kill thyroid cancer.

Prevention

Because the exact cause of thyroid cancer is unknown, finding it early and treating it is the best way to prevent dying from the disease:

  • Aged 20-39, have a thyroid exam every three years.
  • Aged 40 or older, have a thyroid exam every year.

Exposure to radiation is a major risk factor for thyroid cancer, therefore:

  • Avoid unnecessary exposure to radiation.
  • If you have been exposed to radiation of the head, neck, or chest, particularly as a child, have frequent checks for thyroid cancer.

RESOURCES:

American Cancer Society
http://www.cancer.org/

Thyroid Cancer Survivors' Association, Inc.
http://www.thyca.org/

CANADIAN RESOURCES:

Canadian Cancer Society
http://www.cancer.ca/

Thyroid Foundation of Canada
http://www.thyroid.ca/

References:

Beers MH, Fletcher AJ. The Merck Manual of Medical Information—Home Edition. New York, NY: Simon and Schuster, Inc.; 2000.

Bonn D. New hope for thyroid cancer. Lancet. 2000 Aug 26;356(9231):742.

General information about thyroid cancer. National Cancer Institute, National Institutes of Health (NIH) website. Available at: http://www.cancer.gov/cancertopics/pdq/treatment/thyroid/patient. Accessed July 2, 2008.

What are the risk factors for thyroid cancer? American Cancer Society website. Available at: http://www.cancer.org/docroot/CRI/content/CRI_2_4_2X_What_are_the_risk_factors_for_thyroid_cancer_43.asp?sitearea=. Updated October 3, 2007. Accessed July 2, 2008.

Ziegler J. What causes thyroid cancer? J Natl Cancer Inst1997 Dec; 89:1754.



Last reviewed February 2008 by Rimas Lukas, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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