Thyroid cancer is a cancer that starts in the thyroid gland. The thyroid gland is located inside the front of your lower neck.A.D.A.M.

Causes, incidence, and risk factors

Thyroid cancer can occur in all age groups.

Radiation increases the risk of developing thyroid cancer. Exposure may occur from:

• Radiation therapy to the neck (especially in childhood)
• Radiation exposure from nuclear plant disasters

Other risk factors are a family history of thyroid cancer and chronic goiter.

There are several types of thyroid cancer:

• Anaplastic carcinoma (also called giant and spindle cell cancer) is the most dangerous form of thyroid cancer. It is rare, and spreads quickly.
• Follicular carcinoma is more likely to come back and spread.
• Medullary carcinoma is a cancer of non-thyroid cells that are normally present in the thyroid gland. This form of thyroid cancer tends to occur in families.
• Papillary carcinoma is the most common type, and it usually affects women of childbearing age. It spreads slowly and is the least dangerous type of thyroid cancer.

Symptoms

Symptoms vary depending on the type of thyroid cancer, but may include:

• Cough
• Difficulty swallowing
• Enlargement of the thyroid gland
• Hoarseness or changing voice
• Neck swelling
• Thyroid lump (nodule)

Signs and tests

Your health care provider will perform a physical exam. This may reveal a lump in the thyroid, or swollen lymph nodes in the neck.

The following tests may be done:

• Calcitonin blood test to check for medullary cancer
• Laryngoscopy
• Thyroid biopsy
• Thyroid scan
• TSH, free T4
• Ultrasound of the thyroid

Treatment

Treatment depends on the type of thyroid cancer.

Surgery is most often done. The entire thyroid gland is usually removed. If the doctor suspects that the cancer has spread to lymph nodes in the neck, these will also be removed.

Radiation therapy may be done with or without surgery. It may be performed by:

• Aiming external beam (x-ray) radiation at the thyroid
• Taking radioactive iodine by mouth

After treatment for thyroid cancer you must take thyroid hormone pills for the rest of your life. The dosage is usually slightly higher than what your body needs. This helps keep the cancer from coming back.

If the cancer does not respond to surgery or radiation and has spread to other parts of the body, chemotherapy may be used. This is only effective for a small number of patients.

Complications

Complications of thyroid cancer may include:

• Injury to the voice box and hoarseness after thyroid surgery
• Low calcium level from accidental removal of the parathyroid glands during surgery
• Spread of the cancer to the lungs, bones, or other parts of the body

Calling your health care provider

Call your health care provider if you notice a lump in your neck.

Prevention

There is no known prevention. Awareness of risk (such as previous radiation therapy to the neck) can allow earlier diagnosis and treatment.

Sometimes, people with strong family histories and genetic mutations related to thyroid cancer will have their thyroid gland removed for preventive purposes.

References

1. Cooper DS, Doherty GM, Haugen BR et al. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2009;19:1167-1214. [PubMed: 19860577]
2. Lal G, O'Dorisio T, McDougall R, Weigel RJ. Cancer of the endocrine system. In: Abeloff MD, Armitage JO, Niederhuber JE, et al., eds. Abeloff’s Clinical Oncology. 4th ed. Philadelphia, PA: Elsevier Churchill-Livingstone; 2008:chap 75.
3. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Thyroid Carcinoma. Version 1.2013. Available at http://www.nccn.org/professionals/physician_gls/PDF/thyroid.pdf. Accessed 03/11/2013.

Review Date: 3/4/2013.

Reviewed by: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Blackman, Stephanie Slon, and Nissi Wang.