Frequently Asked Questions about Thyroid Cancer
Q: What is the thyroid?
A: The thyroid gland is under the Adam's apple in the front part of the neck. In most people, it cannot be seen or felt. It is butterfly shaped, with 2 lobes -- the right lobe and the left lobe -- joined by a narrow isthmus. The thyroid gland contains mainly 2 types of cells -- thyroid follicular cells and C cells (also called parafollicular cells). The follicular cells use iodine from the blood to make thyroid hormone, which helps regulate a person's metabolism. Too much thyroid hormone (a condition called hyperthyroidism) can cause a rapid or irregular heartbeat, trouble sleeping, nervousness, hunger, weight loss, and a feeling of being too warm. Too little hormone (called hypothyroidism) causes a person to slow down, feel tired, and gain weight. The amount of thyroid hormone released by the thyroid is regulated by the pituitary gland at the base of the brain, which makes a substance called thyroid-stimulating hormone (TSH).
Q: What are the different types of thyroid cancer?
A: Differentiated thyroid cancers develop from thyroid follicular cells. In these cancers, the cells appear similar to normal thyroid tissue when looked at under a microscope.
Papillary carcinoma: About 8 out of 10 thyroid cancers are papillary carcinomas (also called papillary cancers or papillary adenocarcinomas). Papillary carcinomas typically grow very slowly. Usually they develop in only one lobe of the thyroid gland, but sometimes they occur in both lobes. Even though they grow slowly, papillary carcinomas often spread to the lymph nodes in the neck. But most of the time, this can be successfully treated and is rarely fatal.
Follicular carcinoma: Follicular carcinoma is the next most common type of thyroid cancer. It is also sometimes called follicular cancer or follicular adenocarcinoma. Follicular cancer is much less common than papillary thyroid cancer, making up about 1 out of 10 thyroid cancers. It is more common in countries where people don't get enough iodine in their diet. These cancers usually remain in the thyroid gland. Unlike papillary carcinoma, follicular carcinomas usually don't spread to lymph nodes, but some can spread to other parts of the body, such as the lungs or bones. The prognosis for follicular carcinoma is probably not quite as good as that of papillary carcinoma, although it is still very good in most cases.
Hürthle cell carcinoma, also known as oxyphil cell carcinoma, is actually a kind of follicular carcinoma. This type accounts for about 4% of thyroid cancers. The prognosis may not be as good as for typical follicular carcinoma because this subtype is harder to find and treat (it does not absorb radioactive iodine well).
Other Types of Thyroid Cancers
Medullary thyroid carcinoma (MTC): Medullary thyroid carcinoma accounts for about 5% of thyroid cancers. It develops from the C cells of the thyroid gland. Sometimes this cancer can spread to lymph nodes, the lungs, or liver even before a thyroid nodule is discovered or a screening test is done. These cancers usually make calcitonin and carcinoembryonic antigen (CEA), which can be found by blood tests. Calcitonin is a hormone that helps control the amount of calcium in blood. CEA is a protein made by certain cancers, such as colorectal cancer and MTC. Because medullary cancer does not absorb or take up radioactive iodine (used for treatment and to find metastases), the prognosis (outlook) is not quite as good as that for differentiated thyroid cancers.
There are 2 types of MTC. The first type, occurring in about 8 out of 10 cases, is called sporadic MTC. Sporadic MTC is not inherited; that is, it does not run in families. It occurs mostly in older adults and in only 1 thyroid lobe. The other type of MTC is inherited and can occur in each generation of a family. These familial MTCs often develop during childhood or early adulthood and can spread early. They are often linked with an increased risk of other types of tumors.
Anaplastic carcinoma: Anaplastic carcinoma (also called undifferentiated carcinoma) is a rare form of thyroid cancer, making up about 2% of all thyroid cancers. It is thought to develop from an existing papillary or follicular cancer. This cancer is called "undifferentiated" because the cancer cells do not look very much like normal thyroid tissue cells under the microscope. This is an aggressive cancer that rapidly invades the neck, often spreads to other parts of the body, and is very hard to treat.
Thyroid lymphoma: Lymphoma is very uncommon in the thyroid gland. Lymphomas are cancers that develop from lymphocytes, the main cell type of the immune system. Most lymphocytes are found in lymph nodes, which are pea-sized collections of immune cells scattered throughout the body (including the thyroid gland).
Thyroid sarcoma: These rare cancers start in the supporting cells of the thyroid. They are often aggressive and hard to treat.
Parathyroid Cancer: Behind, but attached to, the thyroid gland are 4 tiny glands called the parathyroids. The parathyroid glands help regulate the body's calcium levels. Cancers of the parathyroid glands are very rare -- there are probably fewer than 100 cases each year in the United States. Parathyroid cancers cause the blood calcium level to be elevated. This causes a person to become tired, weak, and drowsy. High calcium also makes you urinate (pee) a lot causing dehydration, which can make the weakness and drowsiness worse. Parathyroid cancer may also be detected as a thyroid nodule if it grows too large. No matter how large the nodule is, the only treatment is to remove it surgically. Unfortunately, parathyroid cancer is much harder to cure than thyroid cancer. The remainder of this document only discusses thyroid cancer.
Q: What are the key statistics about thyroid cancer?
A: The American Cancer Society's most recent estimates for thyroid cancer in the United States are for 2009:
- about 37,200 new cases of thyroid cancer (27,200 in women, and 10,000 in men
- 1,630 deaths (940 women and 690 men).
In general, this is one of the least deadly cancers. The 5-year survival rate (the percentage of people living at least 5 years after being diagnosed) for all cases is about 97%.
Thyroid cancer is different from many other adult cancers in that it mainly affects younger people. Nearly 2 of 3 cases are found in people between the ages of 20 and 55.
Q: What are the risk factors for thyroid cancer?
- Gender and Age: For unclear reasons thyroid cancers occur about 3 times more often in women than in men. Thyroid cancers can occur in people of all ages, but most cases of papillary and follicular thyroid cancer are found in people between the ages of 20 and 60 years.
- Diet Low in Iodine: Follicular thyroid cancers are more common in areas of the world where people's diets are low in iodine. In the United States, dietary iodine is plentiful because iodine is added to table salt and other foods. A diet low in iodine may also increase the risk of papillary cancer if the person also is exposed to radioactivity.
- Radiation: Exposure to radiation is a proven risk factor for thyroid cancer. Sources of such radiation include certain medical treatments and radiation fallout from power plant accidents or nuclear weapons.
- Having a history of head or neck radiation treatments in childhood is a risk factor for thyroid cancer. In the past, children were sometimes treated with radiation for things we wouldn't use radiation for now, like acne, fungus infections of the scalp (ringworm), an enlarged thymus gland, or to shrink tonsils or adenoids. Years later, studies linked these treatments to an increased risk of thyroid cancer.
- Radiation therapy in childhood for some cancers such as Hodgkin disease also increases risk. In general, the risk is higher with younger children. Radiation exposure as an adult carries little risk of thyroid cancer.
- Several studies have pointed to an increased risk of thyroid cancer in children because of radioactive fallout from nuclear weapons or power plant accidents.
- Hereditary Conditions: Several inherited conditions have been linked to different types of thyroid cancer.
Medullary thyroid cancer (MTC): About 1 out of 5 medullary thyroid carcinomas (MTCs) result from inheriting an abnormal gene. These cases are known as familial medullary thyroid carcinoma (FMTC). FMTC can occur alone, or it can be seen along with other tumors.
The combination of FMTC and tumors of other endocrine glands is called multiple endocrine neoplasia type 2 (MEN 2). There are 2 subtypes, MEN 2a and MEN 2b:
- In MEN 2a, MTC occurs along with pheochromocytomas (tumors in the adrenal glands, which are located on top of the kidneys) and with parathyroid gland tumors.
- In MEN 2b, MTC is associated with pheochromocytomas and with benign growths of nerve tissue on the tongue and elsewhere called neuromas. This subtype is much less common than MEN 2a.
In these inherited forms of MTC, the cancers often develop during childhood or early adulthood and can spread early. MTC is most aggressive in the MEN 2b syndrome. If MEN 2a, MEN 2b, or isolated FMTC runs in your family, then you may be at very high risk of developing MTC. Ask your doctor for information about having regular blood tests to look for problems and the possibility of genetic testing.
Other thyroid cancers: People with certain inherited medical conditions are at higher risk for more common forms of thyroid cancer. Higher rates of the disease occur among people with uncommon genetic conditions such as Gardner syndrome, Cowden disease, and familial adenomatous polyposis (FAP). Papillary and follicular thyroid cancers do seem to run in some families without a known inherited syndrome; this may account for about 5% of thyroid cancers. The genetic basis for these cancers is not totally clear.
Q: Can thyroid cancer be prevented?
A: Most people with thyroid cancer have no known risk factors; therefore, it is not possible to prevent most cases of this disease. Some doctors have suggested that the increase in thyroid cancers may be due to x-ray testing of young children. This has not been proven, but it is a good idea for children to avoid x-rays that aren’t necessary. Because of the genetic blood tests now available, most of the familial cases of medullary thyroid carcinoma (MTC) can be treated early or prevented. Once the disease is discovered in a family, the rest of the family can be tested.
If you have a family history of MTC, it is important that you see a doctor who is familiar with the latest advances in genetic counseling and genetic testing for this disease. Removing the thyroid gland in children who carry the abnormal gene will prevent a cancer that might otherwise be fatal.
Q: Can thyroid cancer be found early?
A: Many cases of thyroid cancer can be found early. In fact, most thyroid cancers are now found much earlier than in the past and can be treated successfully. Although it's unusual, some thyroid cancers may not cause symptoms until after they reach an advanced stage. Most early thyroid cancers are found when patients ask their doctors about lumps or nodules they have noticed. Others are found by health care professionals during a routine checkup. Regular blood tests are not recommended to detect sporadic (not familial) thyroid cancers early.
If you have unusual symptoms such as a lump or your neck looks swollen, you should make an appointment to see your doctor right away. During routine physical examinations, be sure your doctor does a cancer-related checkup that, depending on your age, might include examinations for cancers of the thyroid, mouth, skin, lymph nodes, and other cancers. Some doctors recommend that people examine their own necks twice a year to look for any growths or lumps.
People with a family history of medullary thyroid carcinoma (MTC) with or without type 2 multiple endocrine neoplasia (MEN 2) may be at very high risk for developing this cancer. Most doctors recommend genetic testing for these people when they are young to see if they carry the gene for MTC. If a person refuses genetic testing and surgery to prevent MTC, other tests are available that can help find MTC at an early stage when it may still be curable.
Q: What are the signs and symptoms of thyroid cancer?
A: Prompt attention to signs and symptoms is the best approach to diagnose most thyroid cancers early. Thyroid cancer can cause any of the following local signs or symptoms:
- a lump or swelling in the neck, sometimes growing rapidly
- a pain in the front of the neck, sometimes going up to the ears
- hoarseness or other voice change that does not go away
- trouble swallowing
- breathing problems (feeling as if one were "breathing through a straw")
- a cough that continues and is not due to a cold
If you have any of these signs or symptoms, talk to your doctor right away. Many non-cancerous conditions (and some other cancers of the neck area) can cause some of the same symptoms. Thyroid nodules are common and are usually benign. But the only way to find out for sure is to have a medical evaluation. The sooner you receive a correct diagnosis, the sooner you can start treatment and the more effective your treatment will be.
If you have any signs or symptoms that suggest you might have thyroid cancer, your health care professional will want to take a complete medical history. You will be asked questions about your possible risk factors, symptoms, and any other health problems or concerns. If someone in your family has had thyroid cancer (especially medullary thyroid cancer) or adrenal gland tumors called pheochromocytomas, it is important to tell your doctor, as this might indicate you are at high risk for this disease.
A physical exam will give more information about signs of thyroid cancer and other health problems. During the exam, your doctor will pay special attention to the size and firmness of your thyroid and any enlarged lymph nodes in your neck.
Q: How is thyroid cancer treated?
A: Surgery is the main treatment for thyroid cancer and is used in nearly every case, except perhaps some anaplastic thyroid cancers. If the results of fine needle aspiration (FNA) tests indicate thyroid cancer, surgery to remove the tumor and all or part of the remaining thyroid gland is usually recommended.
Lobectomy: This operation is sometimes used for differentiated thyroid cancers that are small and that show no signs of spread beyond the thyroid gland. The lobe containing the cancer is removed, usually along with the isthmus (the small piece of the gland that acts as a "bridge" between the left and right lobes). Because this surgery leaves part of the gland behind, it may not require the lifelong use of thyroid hormone supplements afterward. But having some thyroid left can interfere with some tests to look for cancer recurrence after treatment, such as radioiodine scans.
Thyroidectomy: This operation removes all (total thyroidectomy), nearly all (near-total thyroidectomy) or most (subtotal thyroidectomy) of the thyroid gland. It is the most common surgery for thyroid cancer. It is often used even for differentiated thyroid cancers because papillary thyroid cancer tends to be present in more than one part of the thyroid gland and because follicular cancer is more aggressive.
Lymph Node Removal: When cancer has spread outside of the thyroid gland, surgery is always used to remove as much cancer as possible that has invaded the neck, including cancer that has spread to lymph nodes. This is especially true for treatment of medullary thyroid cancer and for anaplastic cancer (when surgery is an option).
For papillary or follicular cancer where only 1 or 2 enlarged lymph nodes are thought to contain cancer, these enlarged nodes may be removed and any small deposits of cancer cells that are left are treated with radioactive iodine (see below). More often, several lymph nodes near the thyroid are removed in an operation called a central compartment neck dissection. Removal of more lymph nodes, including those on the side of the neck, is called a modified radical neck dissection.
Sentinel lymph node biopsy: Another technique for looking at possible spread to lymph nodes is called a sentinel lymph node biopsy. In this procedure, a radioactive tracer and blue dye are injected into the tumor. The dye and radioactive material travel to the lymph nodes where the cancer would likely spread. The surgeon then removes the sentinel node--the first lymph node into which a tumor drains, and usually the one most likely to contain cancer cells. If the sentinel node is cancer-free, no other lymph nodes are removed. While this technique is used more commonly for some other cancers, the benefit of sentinel lymph node biopsy for thyroid cancer is still unclear.
Q: What happens after treatment for thyroid cancer?
A: After your treatment is over, it is very important to keep all follow-up appointments. During these visits, your doctors will ask about symptoms, examine you, and may order blood tests or imaging studies such as radioiodine scans or CT scans. Follow-up is needed to check for cancer recurrence or spread, as well as possible side effects of certain treatments. This is the time for you to ask your health care team any questions you need answered and to discuss any concerns you might have.
Because most people do very well after treatment, follow-up care can continue for a lifetime. This is very important since thyroid cancers grow slowly and can recur even 10 to 20 years after initial treatment. Your health care team will explain what tests you need and how often they should be done.
If you have had a papillary or follicular cancer, and your thyroid gland has been completely removed and ablated, your doctors will do at least one radioactive iodine scan after your initial treatment is complete. This is usually done about 6 to 12 months later. After that, if it is negative, then you will generally not need further scans unless indicated by other studies or findings. Your blood will also be tested for thyroglobulin. This substance is made by thyroid tissue and, after total thyroid removal and ablation, should be absent from your blood. If thyroglobulin begins to appear, it may be a sign the cancer is coming back, and further testing will be done. This usually includes a radioactive iodine scan, and may include PET scans and other imaging studies. For those with a low-risk, small papillary cancer that was treated by removing only one lobe of the thyroid, a physical exam by your doctor, as well as a thyroid ultrasound and periodic chest x-ray is typical.
If you had medullary thyroid cancer (MTC), your doctors will check your blood levels of calcitonin and carcinoembryonic antigen (CEA). If these begin to rise, imaging tests such as a CT or MRI scan will be done to look for any cancer that may be coming back.
Each type of treatment for thyroid cancer has side effects that may last for a few months. Some, like the need for oral thyroid hormone, may be permanent. You may be able to hasten your recovery by being aware of the side effects before you start treatment. You might be able to take steps to reduce them and shorten the length of time they last. Don't hesitate to tell your cancer care team about any symptoms or side effects that bother you so they can help you manage them.