Health Encyclopedia

Thyroid cancer

Definition

Thyroid cancer is a malignancy (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. This 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 have a higher incidence of thyroid cancer.

Other risk factors are a family history of thyroid cancer and chronic goiter. The disease affects 1 in 1,000 people.

There are several types of thyroid cancer:

Papillary carcinoma is the most common and usually affects women of child-bearing age. It metastasizes (spreads from the original site) slowly and is the least malignant type of thyroid cancer.
Follicular carcinoma accounts for about 30% of all cases and has a greater rate of recurrence and metastasis.
Medullary carcinoma is a cancer of non-thyroid cells in the thyroid gland and tends to occur in families. It requires different treatment from other types of thyroid cancer.
Anaplastic carcinoma (also called giant and spindle cell cancer) is the most malignant form of thyroid cancer. It is rare, but does not respond to radioiodine therapy. Anaplastic carcinoma metastasizes quickly and invades nearby structures such as the trachea, causing compression and breathing difficulties.

Symptoms

Enlargement of the thyroid gland
Neck swelling
A thyroid nodule
Hoarseness or changing voice
Cough or cough with bleeding
Difficulty swallowing

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 that indicate thyroid cancer:

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

This disease may also alter the results of the following tests:

Treatment

Treatment varies depending on the type of tumor.

Surgery is usually the treatment of choice, and the entire thyroid gland is usually removed. If the physician suspects that the cancer has spread to lymph nodes in the neck, these will also be removed during surgery.

Radiation therapy with radioactive iodine is often used with or without surgery. Radiation therapy with beam radiation can also be used.

After treatment, patients need to take thyroid hormone to replace what their glands used to make. The dose is usually a little higher than what the 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 third of the patients.

Support Groups

The stress of the illness can often be eased by joining a support group of people who share common experiences and problems. See cancer - support group.

Expectations (prognosis)

Anaplastic carcinoma has the worst prognosis (probable outcome) of all the types of thyroid cancer, and has an expected life span of less than 6 months after diagnosis. Follicular carcinomas are often fast growing and may invade other tissues, but the probable outcome is still good -- over 90% of patients are cured.

The outcome with medullary carcinoma varies. Women under 40 years old have a better chance of a good outcome. The cure rate is 40-50%.

Papillary carcinomas are usually slower growing. Most people are cured (over 95%) and have a normal life expectancy.

Complications

Low calcium levels from inadvertent removal of the parathyroid glands during surgery
Injury to the voice box or nerve and hoarseness after surgery
Spread of the cancer to the lung or other parts of the body

Calling your health care provider

Call your health care provider if you notice a nodule or mass in your neck.

Also call if symptoms worsen during treatment.

Prevention

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

Review Date:5/26/2006
Reviewed By:Rita Nanda, M.D., Department of Medicine, Section of Hematology/Oncology, University of Chicago Medical Center, Chicago, IL. Review provided byVeriMed Healthcare Network.

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