Thyroid cancer is the uncontrolled growth of abnormal cells in the thyroid gland. The thyroid gland is shaped like a butterfly and is located under the Adam's apple in the front of the neck. Most cases of thyroid cancer are cured. One of the functions of the thyroid gland is to make thyroid hormone and thyroid hormone requires the use of the element iodine. The thyroid gland possesses specialized functions that can capture and trap the dietary iodine and concentrate it in the gland for production of thyroid hormone. Physicians often times exploit this important function in the treatment of thyroid cancer.

There are two other features in the anatomy of the thyroid gland that are important. First, nestled within the thyroid tissue are the presence of four very small glands called parathyroid glands, which have an important role in regulating the use of calcium in the body. If surgery is done on the thyroid gland, it is important for the surgeon to identify and avoid damaging these small glands.

The nerve that controls the voice box is also very close and related to the thyroid. Thus if surgery is contemplated on the thyroid gland, it is important to recognize this nerve. If it is damaged, permanent hoarseness may result.

The thyroid has two types of cells that produce two hormones that help to regulate body functions.

• Follicular cells in the thyroid produce thyroid hormone called thyroxine, or T-4, which controls the body's rate of metabolism. The metabolism regulated by the thyroid gland is a complex process that may affect the function of many different organs in the body.



• C-cells, also called parafollicular cells, produce calcitonin, a hormone that helps to regulate the level of calcium in the blood.

There are five types of thyroid cancers:

• Papillary carcinoma (also known as papillary adenocarcinoma) � This is the most common type of thyroid cancer, accounting for 75 percent of all thyroid cancers. It develops from follicular cells and usually grows slowly. In most cases, it is in only one of the thyroid gland's two lobes, but it affects both lobes in 10 percent to 20 percent of patients. Papillary carcinoma often spreads to nearby lymph nodes in the neck, but also can spread to areas of the body further away.



• Follicular carcinoma � This is the second most common type of thyroid cancer, and it starts in follicular cells. This type of cancer often involves only the thyroid gland, but it sometimes spreads to other body areas, especially the lungs and bone. Only about one-third of tumors beginning in follicular cells are cancerous. Some thyroid cancers are mixtures of papillary and follicular cells.



• H�rthle cell neoplasm (follicular adenocarcinoma) � This is a poorly understood cancer that is similar to follicular carcinoma.



• Anaplastic carcinoma (undifferentiated thyroid cancer) � This is the rarest form of thyroid cancer, and it has the worst prognosis. Scientists believe that it develops from existing papillary or follicular carcinoma. Anaplastic carcinoma is aggressive and spreads quickly to the neck and other parts of the body. Because of the close proximity of the thyroid to the wind pipe (trachea), patients with this type of cancer may experience acute onset of shortness of breath and may require emergency insertion of a tube into the windpipe to aid in breathing.



• Medullary thyroid carcinoma (MTC) � This is the only type of thyroid cancer that develops from the thyroid's C-cells. It can spread to the lymph nodes, the lungs and the liver even before a thyroid nodule (abnormal lump in the thyroid) has been detected. MTC produces the hormone calcitonin, as well as a protein called carcinoembryonic antigen (CEA). Both of these chemicals are released into the blood. There are two main types of MTC. Sporadic MTC (80 percent of all MTC cases) is not inherited and usually develops in only one thyroid lobe. Familial MTC (20 percent of cases) has two forms, each of which can affect several generations of the same family.

In very rare circumstances, tumors arising from connective tissue (sarcomas) and lymph nodes (lymphomas) also can start in the thyroid gland. These are treated differently from other thyroid cancers.

Although scientists have not identified the exact cause of thyroid cancer, some studies have shown that people exposed to nuclear fallout or nuclear power plant accidents have a higher risk of developing thyroid cancer. In part, this is due to the presence of radioactive iodine that may be a part of nuclear fallout. Because the thyroid has an attraction for iodine, the thyroid tissue accumulates this radioactive substance, which over time may cause cancer. People who have received high-dose radiation for acne or swollen adenoids as a child are at increased risk. The incidence of thyroid cancer also is higher in countries where diets are low in iodine. In addition, people with certain medical conditions, such as Cowden's disease and familial polyposis, have a higher risk of developing thyroid cancer.

Individuals who have received radiation therapy to the body in the chest area (for example, Hodgkin's disease and other childhood cancers) have a definite increase incidence of thyroid abnormalities, including cancer, especially if the thyroid was included in the radiation field. Patients will need life-long follow up to both assess the function of the thyroid as well as the presence of cancer.

Some forms of thyroid cancer are inherited. These occur alone (inherited MTC) or as part of a familial cancer syndrome known as multiple endocrine neoplasia (MEN) type 2. Patients with MEN-2 develop tumors in other organs such as the adrenal gland (pheochromocytomas) and peripheral nervous system (neuromas and ganglioneuromas).

Recent scientific studies also indicate that some forms of thyroid cancer may be caused by changes (mutations) in DNA, the chemical matter that makes you unique.

Thyroid cancer is rare, accounting for only about 1.5 percent of all types of cancer. This cancer strikes about 18,000 people in the United States each year and causes more than 1,200 deaths. The illness is more common in women than in men.

Usually, a lump in the neck is the only symptom. When other symptoms occur, they include:

• A pain in the neck that may shoot up into the ears
• Difficulty swallowing
• Hoarseness
• Difficulty breathing
• A persistent cough

Some of these symptoms also occur in conditions other than cancer.

During the physical exam, your doctor will feel your neck to evaluate the size and firmness of the thyroid, and to check for any thyroid lumps or enlarged lymph nodes. To help diagnose thyroid cancer, your doctor also may order the following tests:

• Fine-needle aspiration (FNA) of a thyroid nodule � When your doctor has found a thyroid nodule in your neck, this procedure is considered to be the most effective diagnostic test for thyroid cancer. It usually can be performed in your doctor's office. A local anesthetic is injected to numb the skin over the thyroid nodule. Then the doctor inserts a thin needle into the thyroid nodule and withdraws cells and fluid. These are sent to a laboratory and examined under a microscope for signs of cancer. In 60 percent to 80 percent of FNA procedures, laboratory examination shows that the nodule is not cancerous (benign). About 5 percent of cases are diagnosed as cancer. The remaining 15 percent to 35 percent of cases are ruled suspicious, suggesting that cancer may be present.



• Blood calcitonin test � This test is ordered if the doctor suspects MTC.



• Thyroid scan � In this test, a small amount of a radioactive substance either is swallowed or injected into a vein. The radioactive chemical will be taken up by the thyroid gland. A special camera is positioned next to your neck to measure the amounts of radioactive chemicals in the thyroid area. These scans can help doctors to determine whether a nodule in the gland is actively producing thyroid hormone. If it is producing the hormone, cancer is less likely. If you have thyroid cancer, this test may determine whether cancer has spread to other parts of your body, especially after the thyroid gland has been removed surgically.



• Thyroid ultrasound � In this test, sound waves are used to create images of the thyroid without using X-rays. A thyroid ultrasound may help to determine whether a lump is a cyst or tumor.



• Computed tomography (CT) or magnetic resonance imaging (MRI) of the neck � CT is a modified X-ray beam that makes cross-sectional images of the thyroid area. MRI uses large magnets and radio waves to make cross-sectional, computer-generated images of the thyroid gland and nearby structures in the neck.

Thyroid cancer can develop slowly and remain undetected for years. Like other cancers, it will continue to grow and spread until treatment is provided.

Because many people develop thyroid cancer without having any known risk factors for the illness, this form of cancer usually can't be prevented. However, new genetic blood tests can be used to identify people who have a high risk of developing the familial types of MTC. When inherited MTC strikes one family member, all family members can be tested. Those who test positive, without showing symptoms of thyroid cancer, may decide to have the thyroid removed to prevent thyroid cancer. After surgery, these patients need to take thyroid hormones for the rest of their lives.

The American Cancer Society recommends that after age 40, you should have your thyroid examined during your annual routine physicals. For people between the ages of 20 and 39, the thyroid should be examined every three years.

Surgery is the main method used to treat thyroid cancer. A surgeon will remove all of the cancer, as well as all or part of the remaining thyroid and nearby lymph nodes.

Other important parts of the treatment plan may include:

• Thyroid hormone therapy � If the entire thyroid gland is removed surgically, thyroid hormone medication will help to restore normal metabolism and to suppress a pituitary gland hormone that can accelerate the growth of any remaining thyroid cancer cells. A person must take oral thyroid hormone tablets for life.



• Radioactive iodine treatment � Radioactive iodine can be used after thyroid surgery for two reasons. It can destroy any remaining normal thyroid tissue or it can kill remaining cancer cells or treat cancer that has returned. When used to destroy normal tissue, the treatment can be done as an outpatient with relatively low levels of radiation. For treating cancer, much larger doses are used, often in a hospital.



• Chemotherapy � In this treatment, anticancer drugs are taken by mouth or injected into a vein. Side effects can include hair loss, nausea and vomiting. Chemotherapy is used to treat more aggressive forms of thyroid cancer and more advanced cancers.



• External beam radiation therapy � In this treatment, high-energy rays or particles are focused on the cancer to kill cancer cells.

The specific treatment plan depends on the type of thyroid cancer and how far it has spread. Each treatment for thyroid cancer causes side effects that can linger for a few months. Follow-up care can continue for 20 to 30 years.

A blood test called a serum thyroglobulin blood test is done routinely after surgery and other treatments to determine if any active thyroid tissue, including cancerous thyroid cells, is still present.

Contact your doctor if you discover a lump anywhere in your neck. Also seek medical help if you experience persistent neck pain, a persistent cough or any difficulty breathing or swallowing.

Thyroid cancer usually can be cured if it is detected early. There are more than 500,000 survivors of thyroid cancer in the United States. The outlook for follicular and papillary cancers depends on the patient's age, tumor characteristics, whether the cancer has spread, and whether the tumor was completely removed surgically. The prognosis for MTC depends on whether the cancer occurs without a known cause, is inherited alone, or is inherited as part of a cancer syndrome (MEN-2). Regular follow-up exams are critical, because 5 percent to 20 percent of patients will have the tumor come back.

Anaplastic carcinoma is nearly always fatal, with only 3 percent to 17 percent of patients surviving five years after diagnosis.

American Cancer Society (ACS)
1599 Clifton Road, NE
Atlanta, GA 30329-4251
Toll-Free: 1-800-227-2345
http://www.cancer.org/

National Cancer Institute (NCI)
U.S. National Institutes of Health
Public Inquiries Office
Building 31, Room 10A03
31 Center Drive, MSC 8322
Bethesda, MD 20892-2580
Phone: 301-435-3848
Toll-Free: 1-800-422-6237
TTY: 1-800-332-8615
E-Mail: cancergovstaff@mail.nih.gov
http://www.nci.nih.gov/

American Thyroid Association, Inc.
6066 Leesburg Pike
Suite 650
Falls Church, VA 22041
Phone: (703) 998-8890
Fax: (703) 998-8893
E-Mail: admin@thyroid.org
http://www.thyroid.org/