Thyroid cancer

Alternative Names

cancer of the thyroid; follicular tumor of the thyroid; tumor - thyroid

Definition

A malignancy of the thyroid gland.

Causes, Incidence and Risk Factors

Thyroid cancer can occur in all age groups, and especially in people who have had radiation therapy to the neck. Radiation therapy was commonly used in the 1950s to treat enlarged thymus glands, adenoids and tonsils, and skin disorders. A higher incidence of thyroid cancer is present in people who received radiation therapy as children. Other risk factors are a family history of thyroid cancer and chronic goiter. The overall incidence is 1 out of 1,000 people.
There are several different types of thyroid cancer. Papillary carcinoma is the most common and usually affects women of child-bearing age. It metastasizes 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 can produce symptoms similar to Cushing's syndrome and tends to occur in families. Anaplastic carcinoma (also called giant and spindle cell cancer is the most malignant form of thyroid cancer and does not respond to radioiodine therapy. It metastasizes quickly and invades nearby structures such as the trachea, causing compression and breathing difficulties.

Symptoms

• enlargement of thyroid gland or neck swelling
• hoarseness or changing voice
• cough or cough with bleeding
• diarrhea or constipation

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

Signs And Tests

A physical examination reveals enlarged cervical lymph nodes. An examination of the thyroid reveals single or multiple nodules.
Tests that indicate thyroid cancer:

• a thyroid biopsy showing anaplastic, follicular, medullary, or papillary carcinoma cells
• an ultrasound of the thyroid revealing nodule
• a thyroid scan showing cold nodule
• a laryngoscopy showing paralyzed vocal cords
• serum calcitonin, elevated

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

• T4
• T3
• dexamethasone suppression test
• CEA

Treatment

Treatment varies depending on the type of tumor.
A partial or total surgical resection of the thyroid gland with resection of lymph nodes or radical neck dissection may be necessary.
Radiation therapy with radioactive iodine is sometimes used.
If the tumor is accompanied by hyperthyroidism, thyroid stimulation hormone suppression, in combination with beta-blockers (propranolol), may increase tolerance for surgery or radiation therapy.
Limited chemotherapy may be used for widespread metastasis (spreading) of tumor.
The stress of illness can often be helped by joining a support group where members share common experiences and problems. See cancer - support group.

Expectations (Prognosis)

Anaplastic carcinoma has the worst prognosis (probable outcome). One variety of this cancer, the giant cell type, cares an expected life span of less than 6 months after diagnosis. The small cell variety may have an expected life span of up to 5 years after diagnosis.
Follicular carcinomas are often fast growing and may invade other tissues, but the probable outcome is still good.
The outcome with medullary carcinoma varies. Women under 40 years old have a better chance of a good outcome. The 10-year survival rate (number of people who live at least 10 years after diagnosis) is 46%.
Papillary carcinomas are not associated with a high degree of progression. Many people have a normal life expectancy, if diagnosis is made early.

Complications

• inadvertent removal of the parathyroid glands during surgery
• metastasis of the lung or other body tissues or organs

Prevention

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

Thyroid cancer - CT scan

This CT scan of the upper chest (thorax) shows a malignant thyroid tumor (cancer). The dark area around the trachea (marked by the white U-shaped tip of the respiratory tube) is an area where normal tissue has been eroded and died (necrosis) as a result of tumor growth.