Thyroid cancer is a growth of cells that starts in the thyroid. The thyroid is a butterfly-shaped gland located at the base of the neck, just below the Adam's apple. The thyroid produces hormones that regulate heart rate, blood pressure, body temperature and weight.

Thyroid cancer might not cause any symptoms at first. But as it grows, it can cause signs and symptoms, such as swelling in your neck, voice changes and difficulty swallowing.

Several types of thyroid cancer exist. Most types grow slowly, though some types can be very aggressive. Most thyroid cancers can be cured with treatment.

Thyroid cancer rates seem to be increasing. The increase may be caused by improved imaging technology that allows health care providers to find small thyroid cancers on CT and MRI scans done for other conditions (incidental thyroid cancers). Thyroid cancers found in this way are usually small cancers that respond well to treatments.

Symptoms

Most thyroid cancers don't cause any signs or symptoms early in the disease. As thyroid cancer grows, it may cause:

• A lump (nodule) that can be felt through the skin on your neck
• A feeling that close-fitting shirt collars are becoming too tight
• Changes to your voice, including increasing hoarseness
• Difficulty swallowing
• Swollen lymph nodes in your neck
• Pain in your neck and throat

When to see a doctor

If you experience any signs or symptoms that worry you, make an appointment with your health care provider.

Causes

Thyroid cancer happens when cells in the thyroid develop changes in their DNA. A cell's DNA contains the instructions that tell the cell what to do. The changes, which doctors call mutations, tell the cells to grow and multiply rapidly. The cells go on living when healthy cells would naturally die. The accumulating cells form a mass called a tumor.

The tumor can grow to invade nearby tissue and can spread (metastasize) to the lymph nodes in the neck. Sometimes the cancer cells can spread beyond the neck to the lungs, bones and other parts of the body.

For most thyroid cancers, it's not clear what causes the DNA changes that cause the cancer.

Types of thyroid cancer

Thyroid cancer is classified into types based on the kinds of cells found in the tumor. Your type is determined when a sample of tissue from your cancer is examined under a microscope. The type of thyroid cancer is considered in determining your treatment and prognosis.

Types of thyroid cancer include:

• Differentiated thyroid cancers. This broad category includes types of thyroid cancer that start in the cells that produce and store thyroid hormones. These cells are called follicular cells. Differentiated thyroid cancers cells appear similar to healthy cells when viewed under a microscope.
  • Papillary thyroid cancer. This is the most common type of thyroid cancer. It can happen at any age, but it most often affects people ages 30 to 50. Most papillary thyroid cancers are small and respond well to treatment, even if the cancer cells spread to the lymph nodes in the neck. A small portion of papillary thyroid cancers are aggressive and may grow to involve structures in the neck or spread to other areas of the body.
  • Follicular thyroid cancer. This rare type of thyroid cancer usually affects people older than 50. Follicular thyroid cancer cells don't often spread to the lymph nodes in the neck. But some large and aggressive cancers may spread to other parts of the body. Follicular thyroid cancer most often spreads to the lungs and bones.
  • Hurthle cell thyroid cancer. This rare type of thyroid cancer was once considered a type of follicular thyroid cancer. Now it is considered its own type because the cancer cells behave differently and respond to different treatments. Hurthle cell thyroid cancers are aggressive and can grow to involve structures in the neck and spread to other parts of the body.
  • Poorly differentiated thyroid cancer. This rare type of thyroid cancer is more aggressive than other differentiated thyroid cancers and often doesn't respond to the usual treatments.
• Anaplastic thyroid cancer. This rare type of thyroid cancer grows quickly and can be difficult to treat. However, treatments can help slow the progression of the disease. Anaplastic thyroid cancer tends to occur in people older than 60. It can cause severe signs and symptoms, such as neck swelling that worsens very quickly and may lead to difficulty breathing and swallowing.
• Medullary thyroid cancer. This rare type of thyroid cancer begins in thyroid cells called C cells, which produce the hormone calcitonin. Elevated levels of calcitonin in the blood can indicate medullary thyroid cancer at a very early stage. Some medullary thyroid cancers are caused by a gene called RET that's passed from parents to children. Changes in the RET gene can cause familial medullary thyroid cancer and multiple endocrine neoplasia, type 2. Familial medullary thyroid cancer increases the risk of thyroid cancer. Multiple endocrine neoplasia, type 2, increases the risk of thyroid cancer, adrenal gland cancer and other types of cancers.
• Other rare types. Other very rare types of cancer can start in the thyroid. These include thyroid lymphoma, which begins in the immune system cells of the thyroid, and thyroid sarcoma, which begins in the connective tissue cells of the thyroid.

Risk factors

Factors that may increase the risk of thyroid cancer include:

• Female sex. Thyroid cancer occurs more often in women than in men. Experts think it may be related to the hormone estrogen. People who are assigned female sex at birth generally have higher levels of estrogen in their bodies.
• Exposure to high levels of radiation. Radiation therapy treatments to the head and neck increase the risk of thyroid cancer.
• Certain inherited genetic syndromes. Genetic syndromes that increase the risk of thyroid cancer include familial medullary thyroid cancer, multiple endocrine neoplasia, Cowden syndrome and familial adenomatous polyposis. Types of thyroid cancer that sometimes run in families include medullary thyroid cancer and papillary thyroid cancer.

Complications

Thyroid cancer that comes back

Thyroid cancer can return despite successful treatment, and it can even come back if you've had your thyroid removed. This could happen if cancer cells spread beyond the thyroid before it's removed.

Most thyroid cancers aren't likely to recur, including the most common types of thyroid cancer — papillary thyroid cancer and follicular thyroid cancer. Your health care provider can tell you if your cancer has an increased risk of recurring based on the particulars of your cancer.

Recurrence is more likely if your cancer is aggressive or if it grows beyond your thyroid. When thyroid cancer recurrence happens, it's usually found in the first five years after your initial diagnosis.

Thyroid cancer that comes back still has a good prognosis. It's often treatable, and most people will have successful treatment.

Thyroid cancer may recur in:

• Lymph nodes in the neck
• Small pieces of thyroid tissue left behind during surgery
• Other areas of the body, such as the lungs and bones

Your health care provider may recommend periodic blood tests or thyroid scans to check for signs that your cancer has returned. At these appointments, your provider may ask if you've experienced any signs and symptoms of thyroid cancer recurrence, such as:

• Neck pain
• A lump in the neck
• Trouble swallowing
• Voice changes, such as hoarseness

Thyroid cancer that spreads (metastasizes)

Thyroid cancer sometimes spreads to nearby lymph nodes or to other parts of the body. The cancer cells that spread might be found when you're first diagnosed or they might be found after treatment. The great majority of thyroid cancers don't ever spread.

When thyroid cancer spreads, it most often travels to:

• Lymph nodes in the neck
• Lungs
• Bones
• Brain
• Liver
• Skin

Thyroid cancer that spreads might be detected on imaging tests, such as CT and MRI, when you're first diagnosed with thyroid cancer. After successful treatment, your health care provider might recommend follow-up appointments to look for signs that your thyroid cancer has spread. These appointments might include nuclear imaging scans that use a radioactive form of iodine and a special camera to detect thyroid cancer cells.

Prevention

Doctors aren't sure what causes the gene changes that lead to most thyroid cancers, so there's no way to prevent thyroid cancer in people who have an average risk of the disease.

Prevention for people with a high risk

Adults and children with an inherited gene that increases the risk of medullary thyroid cancer may consider thyroid surgery to prevent cancer (prophylactic thyroidectomy). Discuss your options with a genetic counselor who can explain your risk of thyroid cancer and your treatment options.

Prevention for people near nuclear power plants

A medication that blocks the effects of radiation on the thyroid is sometimes provided to people living near nuclear power plants in the United States. The medication (potassium iodide) could be used in the unlikely event of a nuclear reactor accident. If you live within 10 miles of a nuclear power plant and are concerned about safety precautions, contact your state or local emergency management department for more information.

Diagnosis

Tests and procedures used to diagnose thyroid cancer include:

• Physical exam. Your health care provider will examine your neck to feel for changes in your thyroid, such as a lump (nodule) in the thyroid. The provider may also ask about your risk factors, such as past exposure to radiation and a family history of thyroid cancers.
• Thyroid function blood tests. Tests that measure blood levels of thyroid-stimulating hormone (TSH) and hormones produced by your thyroid gland might give your health care team clues about the health of your thyroid.

• Ultrasound imaging. Ultrasound uses high-frequency sound waves to create pictures of body structures. To create an image of the thyroid, the ultrasound transducer is placed on your lower neck.

  The way a thyroid nodule looks on an ultrasound image helps your provider determine if it's likely to be cancer. Signs that a thyroid nodule is more likely to be cancerous include calcium deposits (microcalcifications) within the nodule and an irregular border around the nodule. If there's a high likelihood that a nodule might be cancerous, additional tests are needed to confirm the diagnosis and determine what type of thyroid cancer is present.

  Your provider may also use ultrasound to create images of the lymph nodes in the neck (lymph node mapping) to look for signs of cancer.

• Removing a sample of thyroid tissue. During a fine-needle aspiration biopsy, your provider inserts a long, thin needle through your skin and into the thyroid nodule. Ultrasound imaging is typically used to precisely guide the needle. Your provider uses the needle to remove some cells from the thyroid. The sample is sent to a lab for analysis.

  In the lab, a doctor who specializes in analyzing blood and body tissue (pathologist) examines the tissue sample under a microscope and determines whether cancer is present. The results aren't always clear. Some types of thyroid cancer, particularly follicular thyroid cancer and Hurthle cell thyroid cancer, are more likely to have uncertain results (indeterminate thyroid nodules). Your provider may recommend another biopsy procedure or an operation to remove the thyroid nodule for testing. Specialized tests of the cells to look for gene changes (molecular marker testing) also can be helpful.

• An imaging test that uses a radioactive tracer. A radioactive iodine scan uses a radioactive form of iodine and a special camera to detect thyroid cancer cells in your body. It's most often used after surgery to find any cancer cells that might remain. This test is most helpful for papillary and follicular thyroid cancers.

  Healthy thyroid cells absorb and use iodine from the blood. Some types of thyroid cancer cells do this, too. When the radioactive iodine is injected in a vein or swallowed, any thyroid cancer cells in the body will take up the iodine. Any cells that take up the iodine are shown on the radioactive iodine scan images.

• Other imaging tests. You may have one or more imaging tests to help your provider determine whether your cancer has spread beyond the thyroid. Imaging tests may include ultrasound, CT and MRI.
• Genetic testing. A portion of medullary thyroid cancers are caused by inherited genes that are passed from parents to children. If you're diagnosed with medullary thyroid cancer, your provider may recommend meeting with a genetic counselor to consider genetic testing. Knowing that you have an inherited gene can help you understand your risk of other types of cancer and what your inherited gene may mean for your children.

Thyroid cancer staging

Your health care team uses information from your tests and procedures to determine the extent of the cancer and assign it a stage. Your cancer's stage tells your care team about your prognosis and helps them select the treatment that's most likely to help you.

Cancer stage is indicated with a number between 1 and 4. A lower number usually means the cancer is likely to respond to treatment, and it often means the cancer only involves the thyroid. A higher number means the diagnosis is more serious, and the cancer may have spread beyond the thyroid to other parts of the body.

Different types of thyroid cancer have different sets of stages. For instance, medullary and anaplastic thyroid cancers each have their own set of stages. Differentiated thyroid cancer types, including papillary, follicular, Hurthle cell and poorly differentiated, share a set of stages. For differentiated thyroid cancers, your stage may vary based on your age.

Treatment

Your thyroid cancer treatment options depend on the type and stage of your thyroid cancer, your overall health, and your preferences.

Most people diagnosed with thyroid cancer have an excellent prognosis, as most thyroid cancers can be cured with treatment.

Treatment may not be needed right away

Treatment might not be needed right away for very small papillary thyroid cancers (papillary microcarcinomas) because these cancers have a low risk of growing or spreading. As an alternative to surgery or other treatments, you might consider active surveillance with frequent monitoring of the cancer. Your health care provider might recommend blood tests and an ultrasound exam of your neck once or twice a year.

In some people, the cancer might never grow and never require treatment. In others, growth may eventually be detected and treatment can begin.

Surgery

Most people with thyroid cancer that requires treatment will undergo surgery to remove part or all of the thyroid. Which operation your health care team might recommend depends on your type of thyroid cancer, the size of the cancer and whether the cancer has spread beyond the thyroid to the lymph nodes. Your care team also considers your preferences when creating a treatment plan.

Operations used to treat thyroid cancer include:

• Removing all or most of the thyroid (thyroidectomy). An operation to remove the thyroid gland might involve removing all of the thyroid tissue (total thyroidectomy) or most of the thyroid tissue (near-total thyroidectomy). The surgeon often leaves small rims of thyroid tissue around the parathyroid glands to reduce the risk of damage to the parathyroid glands, which help regulate the calcium levels in your blood.
• Removing a portion of the thyroid (thyroid lobectomy). During a thyroid lobectomy, the surgeon removes half of the thyroid. Lobectomy might be recommended if you have a slow-growing thyroid cancer in one part of the thyroid, no suspicious nodules in other areas of the thyroid and no signs of cancer in the lymph nodes.
• Removing lymph nodes in the neck (lymph node dissection). Thyroid cancer often spreads to nearby lymph nodes in the neck. An ultrasound examination of the neck before surgery may reveal signs that cancer cells have spread to the lymph nodes. If so, the surgeon may remove some of the lymph nodes in the neck for testing.

To access the thyroid, surgeons usually make a cut (incision) in the lower part of the neck. The size of the incision depends on your situation, such as the type of operation and the size of your thyroid gland. Surgeons usually try to place the incision in a skin fold where it will be difficult to see as it heals and becomes a scar.

Thyroid surgery carries a risk of bleeding and infection. Damage to your parathyroid glands also can occur during surgery, which can lead to low calcium levels in your body.

There's also a risk that the nerves connected to your vocal cords might not work as expected after surgery, which can cause hoarseness and voice changes. Treatment can improve or reverse nerve problems.

After surgery, you can expect some pain as your body heals. How long it takes to recover will depend on your situation and the type of surgery you had. Most people start to feel recovered in 10 to 14 days. Some restrictions on your activity might continue. For instance, your surgeon might recommend staying away from strenuous activity for a few more weeks.

After surgery to remove all or most of the thyroid, you might have blood tests to see if all of the thyroid cancer has been removed. Tests might measure:

• Thyroglobulin — a protein made by healthy thyroid cells and differentiated thyroid cancer cells
• Calcitonin — a hormone made by medullary thyroid cancer cells
• Carcinoembryonic antigen — a chemical produced by medullary thyroid cancer cells

These blood tests are also used to look for signs of cancer recurrence.

Thyroid hormone therapy

Thyroid hormone therapy is a treatment to replace or supplement the hormones produced in the thyroid. Thyroid hormone therapy medication is usually taken in pill form. It can be used to:

• Replace thyroid hormones after surgery. If your thyroid is removed completely, you'll need to take thyroid hormones for the rest of your life to replace the hormones your thyroid made before your operation. This treatment replaces your natural hormones, so there shouldn't be any side effects once your health care team finds the dose that's right for you.

  You might also need thyroid hormone replacement after having surgery to remove part of the thyroid, but not everyone does. If your thyroid hormones are too low after surgery (hypothyroidism), your health care team might recommend thyroid hormones.

• Suppress the growth of thyroid cancer cells. Higher doses of thyroid hormone therapy can suppress the production of thyroid-stimulating hormone (TSH) from your brain's pituitary gland. TSH can cause thyroid cancer cells to grow. High doses of thyroid hormone therapy might be recommended for aggressive thyroid cancers.

Radioactive iodine

Radioactive iodine treatment uses a form of iodine that's radioactive to kill thyroid cells and thyroid cancer cells that might remain after surgery. It's most often used to treat differentiated thyroid cancers that have a risk of spreading to other parts of the body.

You might have a test to see if your cancer is likely to be helped by radioactive iodine, since not all types of thyroid cancer respond to this treatment. Differentiated thyroid cancer types, including papillary, follicular and Hurthle cell, are more likely to respond. Anaplastic and medullary thyroid cancers usually aren't treated with radioactive iodine.

Radioactive iodine treatment comes as a capsule or liquid that you swallow. The radioactive iodine is taken up primarily by thyroid cells and thyroid cancer cells, so there's a low risk of harming other cells in your body.

Which side effects you experience will depend on the dose of radioactive iodine you receive. Higher doses may cause:

• Dry mouth
• Mouth pain
• Eye inflammation
• Altered sense of taste or smell

Most of the radioactive iodine leaves your body in your urine in the first few days after treatment. You'll be given instructions for precautions you need to take during that time to protect other people from the radiation. For instance, you may be asked to temporarily avoid close contact with other people, especially children and pregnant women.

Injecting alcohol into cancers

Alcohol ablation, which is also called ethanol ablation, involves using a needle to inject alcohol into small areas of thyroid cancer. Ultrasound imaging is used to precisely guide the needle. The alcohol causes the thyroid cancer cells to shrink.

Alcohol ablation may be an option to treat small areas of thyroid cancer, such as cancer that's found in a lymph node after surgery. Sometimes it's an option if you aren't healthy enough for surgery.

Treatments for advanced thyroid cancers

Aggressive thyroid cancers that grow more quickly may require additional treatment options to control the disease. Options might include:

• Targeted drug therapy. Targeted drug treatments focus on specific chemicals present within cancer cells. By blocking these chemicals, targeted drug treatments can cause cancer cells to die. Some of these treatments come in pill form and some are given through a vein.

  There are many different targeted therapy drugs for thyroid cancer. Some target the blood vessels that cancer cells make to bring nutrients that help the cells survive. Other drugs target specific gene changes. Your provider may recommend special tests of your cancer cells to see which treatments might help. Side effects will depend on the specific drug you take.

• Radiation therapy. External beam radiation uses a machine that aims high-energy beams, such as X-rays and protons, to precise points on your body to kill cancer cells. Radiation therapy might be recommended if your cancer doesn't respond to other treatments or if it comes back. Radiation therapy can help control pain caused by cancer that spreads to the bones. Radiation therapy side effects depend on where the radiation is aimed. If it's aimed at the neck, side effects might include a sunburn-like reaction on the skin, a cough and painful swallowing.
• Chemotherapy. Chemotherapy is a drug treatment that uses chemicals to kill cancer cells. There are many different chemotherapy drugs that can be used alone or in combination. Some come in pill form, but most are given through a vein. Chemotherapy may help control fast-growing thyroid cancers, such as anaplastic thyroid cancer. In certain situations, chemotherapy might be used for other types of thyroid cancer. Sometimes chemotherapy is combined with radiation therapy. Chemotherapy side effects depend on the specific drugs you receive.
• Destroying cancer cells with heat and cold. Thyroid cancer cells that spread to the lungs, liver and bones can be treated with heat and cold to kill the cancer cells. Radiofrequency ablation uses electrical energy to heat up cancer cells, causing them to die. Cryoablation uses a gas to freeze and kill cancer cells. These treatments can help control small areas of cancer cells.

Supportive (palliative) care

Palliative care is specialized medical care that focuses on providing relief from pain and other symptoms of a serious illness. Palliative care specialists work with you, your family and your health care team to provide an extra layer of support that complements your ongoing care.

Palliative care can be used while undergoing other aggressive treatments, such as surgery, chemotherapy or radiation therapy. Increasingly, palliative care is being offered early in the course of cancer treatment.

When palliative care is used along with all of the other appropriate treatments, people with cancer may feel better, have a better quality of life and live longer.

Palliative care is provided by a team of doctors, nurses and other specially trained professionals. Palliative care teams aim to improve quality of life for people with cancer and their families.

Follow-up tests for thyroid cancer survivors

After your thyroid cancer treatment ends, your provider may recommend follow-up tests and procedures to look for signs that your cancer has returned. You may have follow-up appointments once or twice a year for several years after treatment ends.

Which tests you need will depend on your situation. Follow-up tests may include:

• Physical exam of your neck
• Blood tests
• Ultrasound exam of your neck
• Other imaging tests, such as CT and MRI

Coping and support

It can take time to accept and learn to cope with a thyroid cancer diagnosis. Everyone eventually finds their own way of coping. Until you find what works for you, consider trying to:

• Find out enough about thyroid cancer to make decisions about your care. Write down the details of your thyroid cancer, such as the type, stage and treatment options. Ask your health care provider where you can go for more information. Good sources of information to get you started include the National Cancer Institute, the American Cancer Society and the American Thyroid Association.
• Connect with other thyroid cancer survivors. You might find comfort in talking with people in your same situation. Ask your provider about support groups in your area. Or connect with thyroid cancer survivors online through the American Cancer Society Cancer Survivors Network or the Thyroid Cancer Survivors' Association.
• Control what you can about your health. You can't control whether or not you develop thyroid cancer, but you can take steps to keep your body healthy during and after treatment. For instance, eat a healthy diet full of a variety of fruits and vegetables. Get enough sleep each night so that you wake feeling rested. Try to incorporate physical activity into most days of your week. And find ways to cope with stress.

Preparing for an appointment

If you have signs and symptoms that worry you, start by seeing your family health care provider. If your provider suspects that you may have a thyroid problem, you may be referred to a doctor who specializes in diseases of the endocrine system (endocrinologist).

Because appointments can be brief, and because there's often a lot of information to discuss, it's a good idea to be prepared. Here's some information to help you get ready, and what to expect.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, vitamins or supplements that you're taking. Remember to include any medicines you take that are available without a prescription.
• Take a family member or friend along. Sometimes it can be difficult to recall all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your provider. Write down your top three concerns so that you can be sure to discuss those before moving on to other concerns.

Your time with your provider is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For thyroid cancer, some basic questions to ask include:

• What type of thyroid cancer do I have?
• What stage is my thyroid cancer?
• What treatments do you recommend?
• What are the benefits and risks of each treatment option?
• I have other health problems. How can I best manage them together?
• Will I be able to work and do my usual activities during thyroid cancer treatment?
• Should I seek a second opinion?
• Should I see a doctor who specializes in thyroid diseases?
• How quickly do I need to make a decision about thyroid cancer treatment? Can I take some time to consider my options?
• What might happen if I decide to have regular checkups but not have cancer treatment?
• Are there any brochures or other printed material that I can take with me? What websites do you recommend?
• Am I able to access my medical records through an online patient portal?

If any additional questions occur to you during your visit, don't hesitate to ask.

What to expect from your doctor

Your provider is likely to ask you a number of questions. Being ready to answer them may reserve time to go over points you want to talk about in-depth. Your provider may ask:

• When did you first begin having symptoms?
• Are your symptoms occasional or continuous?
• How severe are your symptoms?
• Does anything seem to improve your symptoms?
• Does anything seem to make your symptoms worse?
• Have you ever been treated with radiation therapy?
• Have you ever been exposed to fallout from a nuclear accident?
• Does anyone in your family have a history of goiter or thyroid or other endocrine cancers?
• Have you been diagnosed with any other medical conditions?
• What medications are you currently taking, including vitamins and supplements?
• What have other health care providers shared with you about your condition?