Thyroid Cancer
Definition
Thyroid cancer is a disease that occurs when abnormal cells begin to grow in the thyroid gland. You may notice a lump in your neck and then go to your doctor. Or your doctor may notice a lump during a routine physical exam or on an imaging test that you are having for another health problem.
Thyroid cancer is usually found before the cancer has spread very far. This means that most people who are treated for thyroid cancer do very well. Treatment for thyroid cancer includes surgery, radioactive iodine treatment, thyroid hormone medicines, and in rare cases, radiation therapy or chemotherapy. After it is treated, thyroid cancer may come back, sometimes many years after treatment.
Before starting your treatment, your doctor needs to find out which of the five types of thyroid cancer you have. A biopsy can identify your type of cancer. During a biopsy, a small piece of thyroid tissue is removed, usually with a needle. The thyroid tissue cells are then examined under a microscope.
It is also important to determine the stage of your cancer. Staging is a way for your doctor to tell how far, if at all, the cancer has spread. It also helps your doctor decide what kind of treatment you need. Staging generally depends on your age and the results of tests done after you have had surgery to remove part or all of your thyroid gland. Sometimes lymph nodes in your neck may also be removed and examined to see if cancer is present.
If you have your thyroid gland surgically removed, you will probably have symptoms of hypothyroidism—a lack of thyroid hormone—and you will need to take thyroid hormone medicines for the rest of your life. These medicines help regulate your metabolism and other body functions that are normally influenced by the thyroid gland. For more information, see the topic Hypothyroidism.
Causes
Experts do not know the exact cause of thyroid cancer. But they do know that people who have been exposed to a lot of radiation—either from the environment or from medical treatment—have a greater chance of developing thyroid cancer. An occasional dental X-ray will not increase your risk of developing thyroid cancer. But past radiation treatment of your head, neck, or chest (especially during childhood) can increase your chances of developing thyroid cancer. Radiation was used from the 1920s to the 1950s to treat problems such as acne or enlarged tonsils, but it is no longer used to treat noncancerous conditions.
One rare type of thyroid cancer, which is called medullary thyroid cancer (MTC), runs in families. You can inherit a specific gene that increases your risk of developing MTC.
Most people do not have any known risk factors for thyroid cancer. If you do have risk factors, they can include:
- A history of radiation treatments to the head, neck, or chest during childhood. Years ago, radiation was used to treat problems such as acne and fungal scalp infections and to shrink the tonsils and adenoids. Radiation exposure in adulthood does not carry the same risk.
- Exposure to high levels of radiation, such as occurred after the Chernobyl nuclear power accident in 1986. The risk is increased most for those who were younger than age 15 when they were exposed to radiation.
- Exposure to fallout from nuclear weapons testing, such as the testing that occurred in the United States during the 1950s. But the radiation exposure from the testing in the 1950s was much lower than at Chernobyl and no increased risk of thyroid cancer at this low level of exposure has been proven.
- A family history of conditions called MEN 2a, MEN 2b, or FMTC (familial medullary thyroid carcinoma). These are caused by an abnormal gene that greatly increases the risk of getting the medullary form of thyroid cancer.
- Other inherited medical conditions, such as Gardner's syndrome and familial polyposis.
- Age. Most cases of thyroid cancer are diagnosed in people who are between the ages of 25 and 65, although it can develop at any age.
- Being female. Thyroid cancer occurs more frequently in women than it does in men.
- Being Asian.
- A diet that is too low in iodine. This is not generally a problem in the United States and Canada, because iodine is added to salt and other foods.
Symptoms
Thyroid cancer can cause many symptoms, including:
- A lump or swelling in your neck. This is the most common symptom.
- Pain in your neck and sometimes in your ears.
- Difficulty swallowing.
- Difficulty breathing or constant wheezing.
- Hoarseness that is not related to a cold.
- A cough that continues and is not related to a cold.
Some people may not have any symptoms. Their doctors may find a lump or nodule in the neck during a routine physical exam.
Exams and Tests
In order to diagnose thyroid cancer, your doctor will ask about your medical history and do a physical exam. Thyroid cancer is most often found during a routine physical exam.
If you have a lump or nodule in your thyroid, your doctor may order a CT scan or an ultrasound to get a better look at your thyroid. If your doctor thinks that the lump or nodule could be cancerous, he or she will do a biopsy of the thyroid gland. A biopsy involves removing a piece of your thyroid, often through a needle. This test is a simple procedure that can be done in your doctor's office.
You may also have certain blood tests.
- Serum thyroglobulin level. Thyroglobulin levels are usually high in people who have thyroid cancer, but your thyroglobulin level can be high even if you don't have cancer.
- Serum calcitonin. If you have medullary thyroid cancer (MTC), your calcitonin level may be high.
- Carcinoembryonic antigen (CEA). This test helps predict how well treatment may work. If your CEA is high, you may have medullary thyroid cancer, which is harder to treat than other types of thyroid cancer.
Other tests may be done before, during, or after your treatment for thyroid cancer.
- Radioactive iodine scans help determine whether thyroid cancer has spread beyond the thyroid gland. These scans are done after surgery to remove the gland.
- Thyroid ultrasound is a safe and simple way to find out whether a thyroid nodule is solid or fluid-filled (cystic). It can also detect multiple thyroid nodules.
- A chest X-ray may help identify thyroid cancer that has spread to the lungs. This is not common.
- A CT scan of the liver may be done to check for any spread of cancer to the liver. This is not common.
In rare cases, when thyroid cancer has significantly spread, an MRI or a PET scan may be done.
If you have medullary thyroid cancer (MTC), a CT scan of the chest and belly and a bone scan may also be needed.
Treatment
You may be shocked to find out that you have thyroid cancer. You may also feel angry, scared, depressed, or anxious. There is no normal or right way to react to or cope with having cancer. Try to remember to take care of yourself and to get help when you need it.
The goal of treatment for thyroid cancer is to get rid of the cancer cells in your body. How this is done depends on your age, the type of thyroid cancer you have, the stage of your cancer, and your general health.
Most people have surgery to remove part or all of the thyroid gland. Sometimes a suspicious lump or nodule has to be surgically removed before you will know if you have cancer or not.
After surgery, you may need treatment with radioactive iodine to destroy any remaining thyroid tissue. When you no longer have all or part of your thyroid gland, you will probably need to take thyroid hormone medicines for the rest of your life. These medicines replace necessary hormones that are normally made by the thyroid gland and prevent you from having hypothyroidism—too little thyroid hormone.
Initial treatment
Your treatment for thyroid cancer may include:
- Surgery to remove the part of the thyroid gland that contains cancer. Removing one part (lobe) is called a lobectomy. Removing both lobes is called a thyroidectomy. Lymph nodes may also be removed during surgery.
- Radioactive iodine, which is used after surgery to destroy any remaining thyroid tissue. After you have your thyroid surgically removed, you may have to wait several weeks before having radioactive iodine treatment to destroy any remaining thyroid tissue. During the waiting period, you may have symptoms of hypothyroidism such as fatigue, weakness, weight gain, depression, memory problems, or constipation. Your doctor may also put you on a low-iodine diet before your treatment. If you are on a low-iodine diet, you cannot eat foods that contain a lot of iodine, such as seafood and baked goods. Depleting your body of iodine may make radioactive iodine treatment more effective because your cells become "hungry" for iodine.
- Foods to avoid in a low-iodine diet include milk and other dairy products, commercial baked products (including most breads), seafood, and red food dye #3. A low-iodine diet is not the same as a low-salt diet. Most salt in the United States and Canada has iodine added, so low-iodine diets avoid iodized salt, but non-iodized salt is okay to eat.
- For more information, talk to your doctor or a registered dietitian, or visit the National Institutes of Health's Web site at: www.cc.nih.gov/ccc/patient_education/pepubs/lowio.pdf.
- Thyroid-stimulating hormone (TSH) suppression therapy. TSH suppression therapy reduces the TSH in your body, which may help prevent the growth of any remaining cancer cells.
- If thyroid cancer is advanced when it is diagnosed, initial treatment may also include chemotherapy or radiation therapy.
Ongoing treatment
After treatment for thyroid cancer, you may need to take thyroid hormone medicine for the rest of your life to replace the hormones that your body no longer makes. You will also need follow-up visits with your doctor every 6 to 12 months. In addition to scheduling regular visits, be sure to call your doctor if you notice another lump in your neck or if you have trouble breathing or swallowing.
At your follow-up visits, your doctor may order:
- A blood test to measure your thyroid-stimulating hormone (TSH) level. This test helps your doctor know if you are taking the right amount of thyroid hormone medicine.
- A blood test to measure your thyroglobulin level. This test helps your doctor know if your cancer has come back. Before this test, you may have to stop taking your thyroid hormone medicine for several weeks. This can cause you to have symptoms of hypothyroidism such as fatigue, weakness, weight gain, depression, memory problems, or constipation.
- Serum calcitonin tests, if you had medullary thyroid cancer (MTC).
- A radioiodine scan to see if the cancer has come back or spread to other parts of your body.
- Other imaging tests to look for signs of cancer, such as ultrasounds, X-rays, CT scans and, in rare cases, MRIs or PET scans.
Treatment if the condition gets worse
Thyroid cancer may come back (recur). If thyroid cancer does recur, it may be found during a physical exam, on an ultrasound, or as a result of increasing thyroglobulin levels. Unlike other types of recurrent cancer, recurrent thyroid cancer is often cured, especially if it has spread only to the lymph nodes in the neck. Recurrent thyroid cancer or thyroid cancer that has spread (metastasized) to other parts of the body is treated with:
- Surgery to remove any remaining thyroid tissue and involved lymph nodes.
- Radioactive iodine.
- Chemotherapy. Medicines such as doxorubicin and cisplatin may be used for certain types of recurrent thyroid cancer.
- Radiation therapy to the neck. This is rarely used.
Before you have a radioactive iodine scan to see if cancer cells have spread (metastasized), you will need to either stop your thyroid hormone replacement for a while or take Thyrogen.
This infomation was taken from the University of Michigan Health System's Health Library.
