Thyroid cancer is the uncontrolled growth of abnormal cells in the thyroid gland. The thyroid gland is shaped like a butterfly. It is located under the Adam's apple in the front of the neck. Most cases of thyroid cancer can be cured.
One of the functions of the thyroid gland is to make thyroid hormone, which requires iodine. The gland collects iodine from foods, concentrates it and produces thyroid hormone. Doctors often exploit this important function when treating thyroid cancer.
Thyroid hormone helps regulate the body's metabolism and energy level. An overactive thyroid can lead to hyperactivity, the "jitters," and an irregular heart rhythm; an underactive thyroid, fatigue and sluggishness. Cancer can affect the thyroid and cause these changes.
Nestled against the thyroid gland are four very small glands called parathyroid glands. They play a role in regulating the body's use of calcium. The nerve that controls the voice box is also very close to the thyroid. If you need a thyroid operation, your surgeon needs to identify and avoid damaging these structures. If the voice box nerve is damaged, for example, your voice may sound hoarse permanently.
The thyroid has two types of cells. They produce hormones that help regulate body functions:
There are five types of thyroid cancers:
Rarely, tumors arising from connective tissue (sarcomas) and lymph nodes (lymphomas) can start in the thyroid gland. They are treated differently than 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. Because the thyroid has an attraction for iodine, the thyroid tissue accumulates this radioactive substance. Over time, it may cause cancer.
Others who have a higher risk of thyroid cancer include people who:
Individuals who have received radiation therapy to the chest (to treat Hodgkin's disease, for example) have an increased incidence of thyroid abnormalities, including cancer. This is even more likely if the thyroid was included in the radiation field. Such people will need life-long follow up to assess thyroid function and check for 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 parts of the body, such as the adrenal gland and peripheral nervous system.
Some forms of thyroid cancer may be caused by genetic changes (mutations) that occur after birth.
Thyroid cancer is rare, accounting for only a small percentage of all cancers. However, it does strike more women than men.
Usually, a lump in the neck is the only symptom of thyroid cancer. When other symptoms occur, they may include:
Often, a patient has no symptoms; the disease is diagnosed based on a test performed for another reason.
Having some of these symptoms does not mean you have thyroid cancer. Symptoms can be caused by other conditions. If you have symptoms, see your doctor so that the problem can be diagnosed and treated.
Your doctor will examine you, feeling your neck to evaluate the size and firmness of the thyroid and to check for lumps and enlarged lymph nodes. Your doctor also may order the following tests and procedures:
CT scans have become a common way to assess many medical conditions. Because the neck is imaged as part of an abdominal scan, thyroid cancer may be detected even though the test was done for another reason.
Thyroid cancer can develop slowly, remaining undetected for years. Like other cancers, it will continue to grow until treated.
Many people have no risk factors for thyroid cancer but develop it anyway. That's why this cancer usually can't be prevented.
However, 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 but have no symptoms of thyroid cancer may decide to have their thyroid removed to prevent the disease. After surgery, these patients need to take thyroid hormones for the rest of their lives.
Surgery is the most common treatment for thyroid cancer. Your surgeon will remove all of the cancer, as well as all or part of the remaining thyroid and nearby lymph nodes.
The treatment of thyroid cancer also is determined by the type of cells that make up the cancer.
Your treatment plan may also include:
A serum thyroglobulin blood test is done routinely after treatment to determine if any active thyroid tissues, including cancerous thyroid cells, are still present.
Recently, several new agents have shown success in treating medullary thyroid carcinoma that was not cured with surgery.
Your treatment plan will depend on the type of thyroid cancer you have and how far it has spread. Each treatment causes side effects that can linger for a few months. Follow-up care can continue for decades.
Contact your doctor if you discover a lump in your neck. Also seek medical help if you have:
Thyroid cancer usually can be cured if it is found early. The outlook depends on your age, the type of cancer, the tumor's characteristics, whether the cancer has spread and whether it was completely removed. The prognosis for MTC depends on whether the cancer occurs with no known cause, is inherited alone or is inherited as part of a cancer syndrome (MEN-2). Regular follow-up exams are critical because the cancer can come back.
Anaplastic carcinoma is nearly always fatal. Only a small percentage of patients survive five years or longer.
American Cancer Society (ACS)
1599 Clifton Rd., NE
Atlanta, GA 30329-4251
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
American Thyroid Association, Inc.
6066 Leesburg Pike
Falls Church, VA 22041