Thyroid Cancer Introduction The thyroid is a gland in the neck. Thyroid cancer is a common type of cancer. It accounts for 1% to 5% of cancer cases worldwide. As medical technology advances, more cases of thyroid cancer are being diagnosed early. The earlier treatment begins, the better the chances of a cure. Most cases of thyroid cancer are curable with treatment. This reference summary will help you better understand what thyroid cancer is and what treatment options are available. The Thyroid Gland Anatomy of the Thyroid The thyroid is a gland located at the front of your neck. It sits beneath your voice box, also called the larynx. If healthy, the thyroid is only a little larger than a quarter. The thyroid has two parts and is shaped like a butterfly. These parts are called lobes. The isthmus is a piece of tissue that separates the two lobes. The thyroid has many types of cells including follicular and C cells. They make several essential hormones including thyroid hormone and calcitonin. Thyroid hormone affects heart rate, blood pressure, body temperature, and weight. It is made by thyroid follicular cells. Calcitonin helps keep a healthy level of calcium in the body. It is made by C cells in the thyroid. Parathyroid glands are attached to and behind the thyroid. There are four or more of these tiny glands. Parathyroid glands make parathyroid hormone. Parathyroid hormone is also important in keeping a healthy level of calcium in the body. Voice Box Isthmus Lobes 1
Thyroid Cancer The body is made up of very small cells. Normal cells in the body grow and die in a controlled way. Sometimes cells keep dividing and growing in an uncontrolled way, causing an abnormal growth called a tumor. Growths on the thyroid are called nodules. More than 90 percent of thyroid nodules are benign, or non-cancerous. Benign tumors are almost never life threatening and usually don t need to be removed. If a nodule is cancerous, it is called malignant. Malignant nodules can be removed but may return. Malignant cells can invade nearby tissues and organs. They can also spread to other parts of the body. Malignant nodules, like many cancerous tumors, can be life threatening. Tumor Cancerous cells may spread to different parts of the body through blood vessels and lymph channels. Lymph is a clear fluid produced by the body that drains waste from cells. It travels through special vessels and bean-shaped structures called lymph nodes. The lymph system branches into all tissues of the body. Cancer treatments are used to kill or control abnormally growing cancerous cells. Cancers in the body are given names, depending on where the cancer started. Cancer that begins in the thyroid will always be called thyroid cancer, even if it spreads to other places. There are several types of thyroid cancer. Papillary, follicular and medullary thyroid cancer are kinds of slow growing thyroid cancer that can be treated easily if found early. Anaplastic thyroid cancer and thyroid lymphoma are more rare types of thyroid cancer. These types of thyroid cancer may be more difficult to treat. Causes and Risk Factors Although health care providers can locate where a cancer started, the cause of cancer cannot usually be identified. Research has shown that people with certain risk factors are more likely than others to develop thyroid cancer. A risk factor is something that may increase the chance of developing a disease. Having one or more risk factors does not mean that a person will get thyroid cancer. It is also possible to develop thyroid cancer without any risk factors. 2
Exposure to high levels of radiation increases a person s risk of developing papillary or follicular thyroid cancer. Between the 1920s and 1950s, health care providers used high-dose x-rays to treat children who had enlarged tonsils, acne or other problems. Some of the people who received these treatments developed thyroid cancer. Today, x-rays use very low doses of radiation. Still, you should talk with your health care providers about limiting your exposure to repeated x-rays unless necessary. Radioactive fallout is another source of radiation. This includes fallout from atomic weapons testing, nuclear power plant accidents and releases from atomic weapons production plants. If you have a family history of thyroid cancer, you are at an increased risk for this type of thyroid cancer. Changes in certain genes can increase the risk of developing thyroid cancer and can be checked with a blood test. Goiters are swollen thyroids. If you or a family member has had a goiter, you are at a greater risk for papillary thyroid cancer. Your risk for papillary thyroid cancer is also increased if you or a family member has had multiple growths on the inside of the colon or rectum. Women are more likely to develop thyroid cancer than men. Also, most people with thyroid cancer are over 45 years old. Iodine level is a possible risk factor for thyroid cancer. Iodine is a substance found in shellfish and iodized salt. Too little iodine in your diet may increase the risk of follicular thyroid cancer. Too much iodine may increase the risk of papillary thyroid cancer. Symptoms The best way to treat thyroid cancer is by finding it early. But early thyroid cancer does not have symptoms. As the cancer grows, symptoms often appear. Common symptoms of thyroid cancer are: A lump in the front of the neck. Hoarseness or voice changes. Swollen lymph nodes in the neck. 3
Trouble swallowing or breathing. Pain in the throat or neck that does not go away. Most often these symptoms are not due to cancer, but anyone with these symptoms should see a health care provider if they do not go away in a couple of weeks. Often these symptoms can be caused by an infection, a benign goiter or another health problem. Diagnosis If your symptoms do not go away in a couple of weeks, you should see your health care provider. Your health care provider will find out whether your symptoms are from thyroid cancer or some other cause. In addition to asking you about your family history, your health care provider may do other tests to diagnose you. Your health care provider will do a physical exam to feel for lumps on your thyroid. Your neck may also be checked for growths and swelling. Blood tests may be done to check for abnormal levels of thyroid-stimulating hormones, or TSH, in your blood. Too much or too little TSH means your thyroid is not working well. Blood tests can also check for high levels of calcitonin, which may indicate medullary thyroid cancer. An ultrasound of the thyroid may also be done. Sound waves are used for this test. The echoes of these waves create pictures of the thyroid. A thyroid scan may be ordered. During a thyroid scan you will be asked to swallow a small amount of a radioactive substance. A scan will then show how much of the substance the nodules absorbed. Nodules that take up less of the substance are called cold nodules. These may be cancer. A biopsy is the only sure way to diagnose thyroid cancer. There are two types of biopsies: fine-needle aspiration and surgical Fine-Needle Aspiration Surgical Biopsy 4
biopsy. A fine-needle aspiration is the most common type of biopsy used to diagnose thyroid cancer. A thin needle is used to remove a sample of tissue from a thyroid nodule. An ultrasound can be used to help guide the needle. A surgical biopsy may be needed if a diagnosis cannot be made from a fine-needle aspiration. A surgeon will remove the whole nodule during a surgical operation. A pathologist will examine the biopsied tissue under a microscope to look for cancer cells. Staging Health care providers do medical tests to find how advanced a cancer is. This is known as staging and helps health care providers determine the best treatment. Stages are usually described using the numbers 1-4. A lower number indicates an earlier stage. Staging is helpful in deciding the best course of treatment. When staging thyroid cancer, health care providers want to find out: The size of the nodule. If the cancer has spread and, if so, to which parts of the body. Your health care provider may order some tests to find out if the thyroid cancer has spread. An ultrasound may show whether cancer has spread to lymph nodes or other tissues near your thyroid. A CT scan may be done to take a series of detailed pictures of your thyroid, lymph nodes and other areas in your neck and chest. A CT scan is an x-ray machine linked to a computer. CT stands for computerized tomography. An MRI may be done to take detailed pictures of areas inside your body. An MRI may show whether cancer has spread to lymph nodes or other areas. MRI is a large machine with a strong magnet. MRI stands for magnetic resonance imaging. A chest x-ray may show whether or not the cancer has spread to your lungs. A whole body scan may show if cancer has spread to other parts of the body. A small amount of a radioactive substance is injected into the bloodstream. Thyroid cancer cells will take up the substance and will show on the scan. 5
Treatment Options The best treatments for you depend on what stage your cancer is in, the type of thyroid cancer and your age. Treatments for thyroid cancer include one or more of the following, which are explained in this section: Surgery. Thyroid Hormone Treatment. Radioactive Iodine Therapy. External Radiation Therapy. Chemotherapy. Surgery External Radiation Therapy Chemotherapy Most people with thyroid cancer have surgery to remove all or parts of the thyroid and other affected tissues. Surgical options may include a total thyroidectomy or a lobectomy. A total thyroidectomy is a procedure that removes the whole thyroid through an incision in the neck. A lobectomy is a procedure that removes one lobe and the isthmus. Remaining tissue can also be destroyed by radioactive iodine therapy if needed. Thyroid hormone treatment can slow the growth of thyroid cancer cells left in the body after surgery. Radioactive iodine therapy, also known as I-131 therapy destroys thyroid cells that remain in the body after surgery. The therapy is given as a liquid or a capsule that you swallow. When thyroid cancer cells take in enough I-131, they die. External radiation therapy is also called radiotherapy. High-energy rays are used to kill cancer cells. Chemotherapy uses drugs to kill cancer cells. The drugs are usually given by injection into a vein. They enter the bloodstream and can affect cancer cells all over the body. There are also clinical trials available for people with thyroid cancer. Clinical trials test new medical approaches and treatments. 6
Follow-up care after treatment for thyroid cancer is important. Blood tests may detect the return of thyroid cancer or another form of cancer. Early detection is important in all forms of cancer. Depending on which treatments you had, you may need to take special supplements for the rest of your life. These pills replace natural thyroid hormones and other vital chemicals created by removed or destroyed tissue. Summary The thyroid is a gland located at the front of your neck. When cancer starts in this gland, it is called thyroid cancer. It is always better to find and treat thyroid cancer early. But early thyroid cancer does not have symptoms. As the cancer grows, symptoms often appear. There are many treatments available for thyroid cancer. Some factors in deciding which treatment is right for you include your age, the stage of thyroid cancer and the type of thyroid cancer. Follow-up care after treatment for thyroid cancer is important. Blood tests may detect the return of thyroid cancer or another form of cancer. Thanks to advances in medical treatment and technology, it is now possible to treat thyroid cancer successfully if the cancer is found early. Make sure to talk with your health care provider if you have any questions. 7