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Thyroid cancer

Definition

Thyroid cancer is a cancerous growth of the thyroid gland.

Alternative Names

Tumor - thyroid; Cancer - thyroid

Causes, incidence, and risk factors

Thyroid cancer can occur in all age groups.

People who have had radiation therapy to the neck are at higher risk. Radiation therapy was commonly used in the 1950s to treat enlarged thymus glands, adenoids and tonsils, and skin disorders. People who received radiation therapy as children are at increased risk for developing thyroid cancer.

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 does not respond to radioiodine therapy. Anaplastic carcinoma spreads quickly and invades nearby structures such as the windpipe (trachea), causing breathing difficulties.
• Follicular carcinoma accounts for about 10% of all cases and is more likely to come back and spread.
• Medullary carcinoma is a cancer of nonthyroid cells that are normally present in the thyroid gland. This form of the thyroid cancer tends to occur in families. It requires different treatment than other types of thyroid cancer.
• Papillary carcinoma is the most common type, and usually affects women of childbearing age. It spreads slowly and is the least dangerous type of thyroid cancer.

Symptoms

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

Note: Symptoms may vary depending on the type of thyroid cancer

Signs and tests

A physical examination can reveal a thyroid mass or nodule (usually in the lower part of the front of the neck), or enlarged lymph nodes in the neck.

Tests for thyroid cancer:

• Elevated serum calcitonin (for medullary cancer) or serum thyroglobulin (for papillary or follicular cancer)
• Laryngoscopy showing paralyzed vocal cords
• Thyroid biopsy showing anaplastic, follicular, medullary, or papillary cancer cells
• Thyroid scan showing a nodule that does not light up on the scan (cold nodule)
• Ultrasound of the thyroid showing a nodule

This disease may also affect the results of the following thyroid function tests:

• T3
• T4
• TSH

Treatment

Treatment varies significantly, depending on the type of tumor.

Surgery is usually the treatment of choice, and 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 during surgery.

Radiation therapy may be performed using external beam (x-ray) radiation or by taking radioactive iodine by mouth. It may be done with or without surgery.

After treatment, you need to take thyroid hormone to replace what your glands used to make. The dose is usually a little higher than what your body needs, which 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, but this is only effective for a small number of patients.

Support Groups

You can ease the stress of illness by joining a support group made up of people who share common experiences and problems. See: Cancer - support group

Expectations (prognosis)

Anaplastic carcinoma has the worst outcome of all the types of thyroid cancer. It is usually fatal despite aggressive treatment.

Follicular carcinomas are often fast growing and may invade other tissues, but the outlook is still good -- most patients are cured.

The outcome with medullary carcinoma varies. Women under age 40 have a better chance of a good outcome.

Papillary carcinomas are usually slower growing. Most people are cured and have a normal life expectancy.

Patients who have treatment for thyroid cancer must take thyroid hormone pills for the rest of their lives.

Complications

• Injury to the voice box or nerve, and hoarseness after surgery
• Low calcium levels 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.

Also call if your symptoms get worse during treatment.

Prevention

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

References

Ladenson P, Kim M. Thyroid. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 244.

National Comprehensive Cancer Network. NCCN Guidelines in Oncology 2010: Thyroid Cancer. Version 1.2010.