MEDICAL CONDITIONS
Thyroid Cancer
The thyroid is a butterfly-shaped gland located in the neck, below the Adam's apple. The thyroid makes and stores hormones that help regulate heart rate, blood pressure, body temperature, and the rate at which food is converted into energy. Thyroid hormones also help children grow and develop. The thyroid uses iodine, a mineral found in some foods and in iodized salt, to make several of its hormones. 
Each year, more than 12,000 Americans find out they have thyroid cancer. This disease accounts for about 1 percent of all cancers. Thyroid cancer usually responds well to treatment, and many patients can be cured.
What are the types of thyroid cancer?
There are four major types of thyroid cancer: papillary, follicular, medullary, and anaplastic. Doctors can tell the type of cancer by the way the cells look under a microscope and by the way the tumor grows.
PAPILLARY TUMORS
Papillary tumors develop in cells that produce thyroid hormones containing iodine. The cancer cells, which grow very slowly, form many tiny, mushroom-shaped patterns in the tumor. Doctors usually can treat these tumors successfully, even when cells from the tumor have spread to nearby lymph nodes. Papillary tumors account for about 60 percent of all thyroid cancers.
FOLLICULAR THYROID TUMORS
Follicular thyroid tumors also develop in cells that produce iodine-containing hormones. These tumors have a thin layer of tissue around them, called a capsule. Many follicular tumors can be cured. However, the disease can be difficult to control if the tumor invades blood vessels or grows through the capsule into nearby structures in the neck. About 17 percent of all thyroid cancers are follicular tumors.
MEDULLARY TUMORS
Medullary tumors affect thyroid cells that produce a hormone that does not contain iodine. Although these tumors grow slowly, they may be harder to control than papillary and follicular tumors. The cancer cells tend to spread to other parts of the body. Only about 5 percent of all thyroid cancers are medullary tumors. It is estimated that 1 out of 10 medullary thyroid cancers is hereditary.
ANAPLASTIC TUMORS
Anaplastic tumors are the fastest growing thyroid tumors. The cancer cells, which are extremely abnormal, spread rapidly to other parts of the body. Anaplastic tumors make up about 18 percent of all thyroid cancers and usually occur in people over 60 years of age.
What causes thyroid cancer?
Doctors do not know what causes most cases of thyroid cancer. However, scientists have observed that thyroid cancer affects women two to three times as often as men and occurs more frequently in whites than in blacks. Scientists do not fully understand the reasons for these patterns; they continue to study thyroid cancer to try to learn what may increase a person's risk for this disease.
One known risk factor is exposure to radiation during childhood. Before doctors knew of its dangers, radiation therapy was used to treat acne and to reduce swelling and infection in organs such as the thymus, tonsils, and lymph nodes. People who received radiation to the head and neck as children have a higher- than-average risk of developing thyroid cancer many years late. Scientists are doing studies to determine whether other types of radiation exposure also can cause thyroid cancer.
Can thyroid cancer be detected early?
The National Cancer Institute recommends that anyone who received radiation to the head or neck in childhood be examined by a doctor every 1 to 2 years. Also, people should see a doctor if they have a family member with medullary thyroid cancer. The most important part of a checkup is the careful examination of the neck, feeling for lumps in the thyroid and enlargement of nearby lymph nodes. A thyroid scan (scintogram) or ultrasonography may be recommended for people at risk for thyroid cancer.
What are symptoms of thyroid cancer?
The most common symptom of thyroid cancer is a lump, or nodule, that can be felt in the neck. Other symptoms are rare. Pain is seldom an early warning sign of thyroid cancer. However, a few patients have a tight or full feeling in the neck, difficulty breathing or swallowing, hoarseness, or swollen lymph nodes. These symptoms can be caused by thyroid cancer or by other, less serious problems. If a person is experiencing symptoms, a doctor should be consulted.
How is thyroid cancer diagnosed?
The doctor can use several tests to learn the size and location of a thyroid nodule and/or to help determine whether a lump is benign (not cancerous) or malignant (cancerous. For example, the doctor may order blood tests to check how well the patient's thyroid is functioning. Also, a radioactive iodine scan can outline abnormal areas of the thyroid. For the scan, the patient is given a very small amount of a radioactive substance (usually iodine I-131 or technetium TC-99m), which collects in the thyroid. An instrument called a scanner can detect "cold spots" (areas in the thyroid that do not absorb iodine normally. Because cold spots can be benign or malignant, further tests are necessary.
Ultrasonography is another technique for producing a picture of the thyroid. In this procedure, high-frequency sound waves, which cannot be heard by humans, pass into the thyroid. The patterns of echoes produced by these waves are converted into a picture (sonogram) by a computer. Doctors can tell whether nodules are fluid-filled cysts, which are usually benign, or solid lumps that might be malignant.
The only sure way to tell whether a patient has thyroid cancer is to look at cells from the thyroid with a microscope. There are two ways to obtain a sample of thyroid tissue: by withdrawing cells using a needle (needle biopsy) or by surgically removing the tumor (surgical biopsy). In either case, a pathologist examines the tissue under a microscope to look for cancer cells.
If the needle biopsy does not show cancer, the doctor may give the patient thyroid hormones. These hormones make it unnecessary for the thyroid to produce its own hormones, and the gland, including the nodule, shrinks and becomes inactive. If the needle biopsy is not conclusive or if the thyroid hormones are not effective, the patient usually has a surgical biopsy.
When thyroid cancer is diagnosed, doctors may do more tests to learn about the stage (extent) of the disease. The results of these tests help doctors plan appropriate treatment.
What treatment is there for thyroid cancer?
Surgery is the most common form of treatment for thyroid cancer that has not spread to distant parts of the body. The surgeon usually removes part or all of the thyroid and any other affected tissue, such as lymph nodes. (If the patient has a surgical biopsy, the biopsy and the removal of the thyroid may be done in the same operation).
Patients with localized papillary or follicular thyroid cancer also may receive treatment with I-131 (a larger dose than that used in a thyroid scan). The patient swallows the iodine, which collects in any thyroid cancer cells that remain in the body after surgery. By damaging such cancer cells, the radioactive iodine helps prevent the disease from recurring. The patient must remain in the hospital for a few days while the radiation is most active. The treatment may be repeated at a later time.
Hormones usually are given to patients who have had surgery to remove the thyroid and/or treatment with radioactive iodine. The hormones replace those that are normally produced by the thyroid. This treatment also slows down the growth of any remaining thyroid cancer cells. The doctor may need to do follow-up tests to determine whether the patient is receiving the proper amount of the necessary hormones.
Surgery may not be recommended when a patient is found to have thyroid cancer that has spread. Treatment usually includes some form of systemic therapy (treatment that can kill or slow the growth of thyroid cancer cells throughout the body), such as chemotherapy, radioactive iodine therapy, and/or hormone therapy.
Regular follow-up is very important after treatment for thyroid cancer. Follow-up care may include periodic complete physician exams, x-rays, scans, and blood tests. Thyroid Cancer At A Glance - The thyroid gland produces thyroid hormones which are important in the normal regulation of the metabolism of the body.
- There are four major types of thyroid cancer.
- The cause of thyroid cancer is unknown, but certain risk factors have been identified.
- The National Cancer Institute recommends that anyone who received radiation to the head or neck in childhood be examined by a doctor every 1 to 2 years.
- The most common symptom of thyroid cancer is a lump, or nodule, that can be felt in the neck.
- The only certain way to tell whether a thyroid lump is cancer is by examining the thyroid tissue obtained using a needle or surgery for biopsy.
- Surgery is the most common form of treatment for thyroid cancer that has not spread to other areas of the body.
For additional information about cancer, write to the Office of Cancer Communications, National Cancer Institute, Bethesda, MD 20892, or call the Cancer Information Service toll free at 1-800-4-CANCER. Spanish-speaking staff members are available.
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