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What Is Thyroid Cancer?

Causes, symptoms, diagnosis, treatments, and support

Featured experts: David Lieb, MD, Avital Harari, MD, and Amy Chen, MD


While thyroid cancer is less prevalent in the United States than many other cancers, an estimated 44,000 people are still diagnosed with it each year, according to the National Cancer Institute (a division of the NIH). It has very good 5-year survival rates — about 98% overall, regardless of the stage at which it is diagnosed. But despite a reputation among some people as a “good cancer” to get, it can still be a traumatic and debilitating experience. We’re here to empower you with clear answers to your pressing Qs.

Overview | Types of Thyroid Cancer | Signs and Symptoms | Causes and Risk Factors | Diagnosis | StagesTreatment | Complications from Treatment | Survival Rates | Support | Fast Facts | Frequently Asked Questions

What Is Thyroid Cancer?

Thyroid cancer is a solid tumor cancer that usually shows up as a nodule, or mass, in the thyroid gland, which is located at the front base of your throat. It occurs when rogue cells reproduce too rapidly for the immune system to control. There are several types of thyroid cancer, but two types — papillary thyroid cancer and follicular thyroid cancer — are by far the most common, accounting for some 95 percent of cases. Between 1% and 2% of people will get thyroid cancer at some point during their lifetime. It affects three times as many women as men and is most common after age 30, though it can occur in any age group. Thyroid cancer is more likely to be aggressive in older adults.

Thyroid Cancer Types

There are four main types of thyroid cancer, which differ in their aggressiveness and other factors:

Papillary Thyroid Cancer

This is by far the most common form of thyroid cancer, accounting for between 80% and 85% of all diagnoses. It’s among the most curable of all cancers.

Follicular Thyroid Cancer

About 10% to 15% of thyroid cancers fall into this category. It’s more aggressive than papillary thyroid cancer and can invade other areas of the body through the bloodstream. A rare form of follicular thyroid cancer known as Hurthle cell cancer is especially aggressive.

Medullary Thyroid Cancer

This accounts for less than 3% of thyroid cancers, according to the American Thyroid Association (ATA). It can, and frequently does, spread to lymph nodes.

Anaplastic Thyroid Cancer

This type of cancer has a poorer prognosis and tends to become resistant to chemotherapy over time. The ATA says less than 2% of thyroid cancers fit into this category. Anaplastic thyroid cancer advances quickly and is the most aggressive thyroid cancer.

The different types of thyroid cancerThe four different types of thyroid cancer.

Thyroid Cancer Symptoms

Thyroid cancer frequently presents with no symptoms, says David Lieb, MD, head of the endocrinology department at the East Virginia Medical School in Norfolk, VA. Most commonly, Dr. Lieb says, a physician finds a nodule — a growth of abnormal thyroid tissue — during an incidental exam (an exam done for another reason).

When thyroid cancer does cause signs or symptoms, the most common one is swelling in your neck. Sometimes, you don’t notice even the growth, but your dentist or spouse might, Dr. Lieb notes. Your thyroid typically still works normally.

In some cases, a person can have thyroid nodules big enough to cause other issues, including:

  • problems swallowing
  • shortness of breath
  • discomfort when moving the head or neck
  • hoarseness
  • changes to the voice
  • a persistent cough

Pain is very uncommon in thyroid cancer, except in some cases of medullary thyroid cancer.

It’s important to note that the large majority of thyroid nodules (more than 90%) do not turn out to be cancerous. Having such nodules is common, especially as you age; half of the population experiences them by age 60, according to the ATA. Nodules are less common in children and younger adults than in older adults, but when they do occur they have a higher likelihood of being cancerous.


What Causes Thyroid Cancer?

It’s not clear exactly what causes thyroid cancer to develop. However, there are a number of known potential risk factors, some of which can be modified and others (like your age and sex) that can’t. According to the National Cancer Institute, risk factors for developing thyroid cancer include:

  • Being female
  • Being between the ages of 25 and 65. (The median age of papillary thyroid cancer patients is 50.)
  • Asian ethnicity
  • Radiation exposure. This includes having had external beam radiation to the head, neck, or chest, or exposure to a radiation event such as the one at Chernobyl, which led to an increase in children with thyroid cancer. The cancer can develop as early as five years after exposure.
  • A history of goiter (enlarged thyroid gland)
  • A family history of thyroid cancer or thyroid disease
  • Having certain genetic mutations. This is especially relevant to medullary thyroid cancer, which runs strongly in families. If you have a family member with medullary thyroid cancer, there is a blood test you can take that looks for a mutation on a specific gene (called RET) that’s associated with the cancer. People who learn they have the mutation sometimes opt to undergo surgery to remove their thyroid (called a thyroidectomy) to decrease their chance of cancer. Even young children can have this surgery.
  • Iodine deficiency. This is a risk factor for follicular thyroid cancer.
  • Being overweight or obese. Heavier individuals have a higher risk of developing thyroid cancer than people who are not overweight, and the risk appears to increase as body mass index (BMI) goes up. Heavier patients also often present at later stages and with more aggressive tumors, according to research done by Avital Harari, MD, an endocrine surgeon at the UCLA Geffen School of Medicine.

Other research led by Dr. Harari is looking at whether certain environmental exposures, including to pesticides and flame retardants, have a link to thyroid cancer.

Thyroid Cancer Diagnosis

If you are referred to a specialist to check for possible thyroid cancer, you can expect to have a biopsy of your thyroid gland —specifically, what’s called a fine needle aspiration biopsy. The sample is then studied under a microscope to determine if a nodule is cancerous or benign.

If a nodule is cancerous, a pathologist will determine the type and the staging of the cancer. You will likely be referred to a surgeon to develop a plan for treatment.

Post-referral, expect your surgeon to take a full medical history and conduct a physical exam. The doctor will need to know if you have issues such as a “hot” thyroid nodule (a nodule that makes too much thyroid hormone) that needs controlling prior to surgery. There will be imaging studies of your neck and surrounding lymph nodes, Dr. Harari says.

“We want to know if there are multiple nodules, evidence of invasion, and the positioning of lymph nodes,” she explains. “We may need to do a CT scan if we think the cancer extends to the lungs.”

These studies will help the surgeon plan your procedure and determine if a vascular surgeon — a surgeon who specializes in treating the circulatory system — or other specialist is required.

What Are the Stages of Thyroid Cancer?

Once you have been diagnosed with thyroid cancer, you will undergo testing to determine how far the cancer has spread, also known as the stage. Knowing the stage of your cancer helps your doctor to decide the most appropriate treatment.

The staging of papillary or follicular thyroid cancers is based on the age of the person at diagnosis — specifically if they are younger or older than age 55 — and the extent to which thyroid cancer cells have spread. The staging of anaplastic and medullary thyroid cancers does not take age into account.

TNM Staging

In staging your cancer, your doctor may refer to the American Joint Committee on Cancer’s TNM system, which provides a common shorthand and helps to illustrate a clearer picture of your cancer. TNM stands for:

  • T – Tumor. What size is your tumor?
  • N – Nodes. Has the cancer spread to your lymph nodes?
  • M – Metastasis. Has the cancer spread further?

Papillary and follicular thyroid cancers are categorized as Stage I, Stage II, Stage III, Stage IVA, or Stage IVB. Medullary thyroid cancer has those stages plus a Stage IVC. All anaplastic thyroid cancers are considered Stage IV; they’re categorized as Stage IVA, IVB, or IVC depending on the extent of spread.

Imaging of a cancerous mass on the thyroid gland.Imaging of a cancerous mass on the thyroid gland (on the patient's right side; left side of the image).

Treatment for Thyroid Cancer

Treatment for thyroid cancer varies based on the type and staging of the cancer, as well as other factors including:

  • your age at diagnosis
  • your general health
  • whether your cancer is newly diagnosed or recurring

Here is a rundown of the treatment options you and your doctor might consider.


Small, isolated papillary and follicular thyroid cancers are often cured with simple surgery alone. The extent and type of surgery varies from person to person and from cancer to cancer.

How much of the thyroid gland to have removed is a discussion between you, your surgeon, and your endocrinologist. “I can present the data,” says Amy Chen, MD, a head and neck surgeon at Emory University in Atlanta. “I may tell the patient it’s okay if they have less than the entire thyroid removed. But sometimes they want it all out, because they are worried about recurrence. And I’ll take it all out.”

Other people come in wanting less surgery than they need, and Dr. Chen says this is more problematic. “It’s a long discussion. The best chance to remove it all is the first chance and if I don’t, it may get worse.”

Dr. Lieb says that before this century, most people with thyroid cancer were all treated the same: surgery and radioactive iodine (RAI) therapy (discussed below). “Now,” however, “we have studies that help guide therapy so that it’s more patient specific,” he says.

In clinical guidelines released in 2015, for example, the ATA developed a system for determining whether a patient is at low, intermediate, or high risk for recurrence or relapse of their thyroid cancer. That information is then used to guide treatment decisions. People with a low risk for recurrence may not need a total thyroidectomy (removal of the entire thyroid gland), according to the guidelines.

In the cases where part of the thyroid is saved, the patient may not even need to take thyroid hormone after surgery, Dr. Lieb says.

Recovery from thyroid surgery is pretty quick, Dr. Harari says. “Even with the really long surgeries, you can walk the same day.” For a couple weeks after surgery, you need to avoid strenuous lifting and exercise, but walking and general movement are fine. Your neck and throat may be sore but should be able to return to work within a few days.

Postsurgical pain is usually managed with acetaminophen after the first day. About half of patients need a narcotic pain reliever the first night, Dr. Harari says.

While some doctors will keep you in the hospital for a couple days, others will avoid using drains to try to ensure you can go home the day of surgery, Dr. Harari says. After surgery, you will see your doctor every 6 or 12 months for follow-up monitoring to ensure the cancer is gone and you are healing well. As part of that monitoring, you may have one or more of these tests:

  • Ultrasound examinations. Your doctor may use these results to determine if there are any signs that your cancer has returned.
  • Blood test for thyroglobulin. After treatment for thyroid cancer, you should not produce any thyroglobulin, a protein made by your thyroid gland. If your test is positive for the protein, it may mean cancer has returned, but it may also only indicate that you have residual thyroglobulin antibodies.
  • Blood test for calcitonin. If you have medullary thyroid cancer (MTC), you may have regular tests for calcitonin, which is produced by cells in the thyroid called C cells. Like thyroglobulin, calcitonin is used as a cancer marker after thyroid surgery.
  • Other imaging studies. MTC patients may also have regular CT scans or MRIs (in addition to ultrasounds) as part of their regular follow-up care.

If you are at a higher risk for recurrence, your doctor may order a full body scan with RAI tracers to detect any thyroid cells that might mean there is a recurrence of thyroid cancer.

Thyroid Hormone Replacement Therapy

Thyroid hormone replacement therapy is often prescribed after thyroid surgery to replace the hormones that are no longer being produced by your (now-removed) thyroid tissue. Depending on how much of your thyroid was taken out, you may have to take the medication — most commonly levothyroxine (brand name Synthroid and others) — for the rest of your life.

Thyroid hormone replacement can also help prevent the growth or recurrence of thyroid cancer. It does this by lowering your circulating level of the hormone TSH, which is secreted by your brain’s pituitary gland and tells your thyroid to make more thyroid hormone. High TSH levels can stimulate the growth of thyroid cancer cells. Higher doses of replacement thyroid hormone tell your body to make less TSH, slowing the growth of any thyroid cancer cells and lowering the odds of your cancer coming back. 

It can take a few adjustments to find the correct dosage of thyroid hormone replacement. During this time, you may need to see the doctor every 6 to 8 weeks for a blood draw to determine if your levels are optimal.

Radioactive Iodine (RAI) Therapy

Thyroid cells are unique in that they are the only cells in your body that can absorb the element iodine, which makes targeting thyroid cancer easier. For a long time, RAI was the treatment of choice following surgery to remove the thyroid. RAI targets any thyroid cells that are left after surgery, destroying them from within.

Those who need RAI treatment take a single pill about 5 to 6 weeks after surgery. For a few days following the treatment, you must avoid other people as you yourself are radioactive for a time.

If you are taking medication for an underactive thyroid (hypothyroidism), you may be asked to stop taking it for a few weeks before RAI treatment. This can lead you to temporarily experience symptoms like fatigue, hair loss, weight gain, and other common symptoms of an underactive thyroid. About a week after the treatment, you can start taking thyroid medications again.

As an alternative to stopping thyroid medication, your doctor might suggest thyrotropin alfa, a recombinant (genetically engineered) form of thyroid hormone. Switching to thyrotropin alfa allows you to continue taking thyroid replacement during RAI treatment. However, Dr. Lieb notes that it is expensive and not all insurers will cover it. The drug is given via injection on the days immediately preceding RAI.

Low Iodine Diet

You may also be asked to go on a low iodine diet during RAI therapy. This means you will have to avoid certain foods including:

  • iodized salt and things that contain it
  • dairy
  • seafood
  • soy products
  • chocolate
  • products containing red dye

If you need to follow a low iodine diet, the Thyroid Cancer Survivors Association (thyca.org) has a cookbook created by members that includes food lists and recipes. “For some people, it is the most frustrating thing about treatment,” says Dr. Lieb.

External Beam Radiation

External beam radiation therapy may be used to target cancer cells that have spread beyond the thyroid gland. It is most commonly used to treat medullary or anaplastic thyroid cancers that do not respond to RAI or other targeted treatments.


Chemotherapy can be used to treat thyroid cancer that has spread beyond the thyroid. The method and dosage are determined based on the type and staging of the cancer. This method is often used to treat anaplastic thyroid cancer due to the speed at which it can progress.

Watchful Waiting, a.k.a. Active Surveillance

Dr. Harari notes that there has been increased interest in “watchful waiting,” also known as active surveillance, for thyroid cancer. “In New York at Memorial Sloan Kettering Cancer Center, it is the standard of care for certain populations,” she says.

Watchful waiting can be a good choice for people who have small nodules that are not growing quickly or are not invasive in nature. It can also be a good treatment option for people who are very worried about having surgery, Dr. Harari says. 

One reason why watchful waiting is garnering interest is that while diagnoses of thyroid cancer have increased over the last decade, mainly as a result of increased imaging done for other purposes, mortality from it hasn’t changed.

“People are having chest CTs for other reasons and they pick it up, or they have a carotid artery ultrasound and see it,” Dr. Lieb says. “But if these nodules hadn’t been discovered, many of them wouldn’t have caused a problem at all; they are small, low-risk cancers.”

Dr. Chen agrees. “The fact that we are finding more and smaller cancers hasn’t impacted the death rate,” she says. “So when we operate on people with small early-stage cancers, we may be doing unnecessary surgery with the potential for complications — because all surgeries have risks. So we have someone who probably wouldn’t die of thyroid cancer, but we have given them a lifelong problem with nerves, voice loss, and hypoparathyroidism [which are complications of thyroid surgery]. It’s not good.”

Research is currently looking at molecular markers that can predict which tumors may be more aggressive and likely to get bigger. Such information might help doctors determine in the future which patients are most likely to benefit from immediate surgery and which can forgo it.

What Are the Side Effects of Thyroid Cancer Treatment?

All medical treatments have potential side effects, including those for thyroid cancer. Here are possible complications you should be aware of if you’re undergoing treatment.

Side Effects of Thyroid Surgery

The risks of thyroid surgery include:

  • Damage to the laryngeal nerve. “It can be stunned, or one vocal cord won’t move the same way as the other,” Dr. Harari explains. About 5% of people temporarily experience this complication, and 1% have permanent damage. There are procedures to regain vocal strength, and an ENT specialist can assist the patient in these efforts.
  • Hypoparathyroidism, or inadequate parathyroid hormone production, as sometimes surgeons decide to remove one or more of the parathyroid glands — four tiny glands that regulate the body’s calcium levels and are located near the back of the thyroid. People whose thyroid surgery involves a central neck incision have a 10% risk of parathyroid complications.
  • Vagus nerve issues. Lateral neck incisions can risk impacting the vagus nerve, Dr. Harari says. This can have effects on the voice (because the laryngeal nerve originates at the vagus nerve) as well as the shoulder or tongue.
  • Loss of thyroid function. After surgery, you will probably need to take pills for the rest of your life to replace lost thyroid hormones. If your parathyroid glands are also removed, you may also need to take calcium and vitamin D.

Side Effects of Thyroid Hormone Treatment

Thyroid hormone pills themselves do not usually cause side effects, but it can take some time to get the dosage right, and you may experience symptoms of either hyperthyroidism or hypothyroidism while you and your doctor work to determine the correct dose. (This will be done through blood testing to monitor your thyroid hormone levels.)

Symptoms of too much thyroid hormone may include:

  • Increased heart rate
  • Weight loss
  • Chest pain
  • Cramps

Symptoms of too little thyroid hormone may include:

  • weight gain
  • fatigue
  • dry skin and hair

Definitely check in with your doctor if you feel you are experiencing any of the above symptoms so that your dosage can be properly adjusted.

Side Effects of Radioactive Iodine Therapy

Side effects from radioactive iodine (RAI) can include:

  • Mild nausea during the first day
  • Swelling and pain in the neck where thyroid cells remain
  • Dry mouth
  • Temporary loss of smell and/or taste

Additionally, high doses of RAI can cause problems with fertility (more common in women than men). They can also kill normal thyroid cells along with the cancerous ones, which can lead to the need for thyroid hormone replacement medication.

If you have to have RAI multiple times, the radiation can increase the risk of some cancers, including leukemia, says Dr. Lieb.

Side Effects of External Beam Radiation Therapy

Side effects depend on the dose, but generally, radiation to the neck may cause:

  • Dry, sore mouth and throat
  • Hoarseness
  • Difficulty swallowing
  • Fatigue

Side Effects of Chemotherapy

Chemotherapy, which is usually only used for anaplastic thyroid cancer, has different side effects depending on the type and dose of drugs given and the length of time for which they are taken. Side effects can include:

  • Hair loss
  • Mouth sores
  • Loss of appetite
  • Nausea and vomiting
  • Diarrhea
  • Increased chance of infections (due to low white blood cell counts)
  • Easy bruising or bleeding (due to low blood platelet counts)
  • Fatigue (due to low red blood cell counts)

Thyroid Cancer Survival Rate

Most thyroid cancers are very curable. In fact, the most common types of thyroid cancer — papillary and follicular cancers — have a more than 98% cure rate if they’re caught and treated at an early stage. The earlier you are diagnosed, the less likely it is that your cancer will have spread beyond the thyroid and the easier it is to treat.  

Medullary thyroid cancer has a worse prognosis and is likely to include lymph node involvement. Once cancer has entered the lymph nodes it spreads readily through the lymphatic system, meaning your cancer will require more extensive and possibly more aggressive treatment.

The least common type of thyroid cancer, anaplastic thyroid cancer, has a very poor prognosis. The best results occur when localized anaplastic thyroid cancer is diagnosed early and completely removed via a thyroidectomy, as it’s very aggressive. Unfortunately, this cancer tends to be found after it has already spread.

Because most people don’t die from thyroid cancer, it’s sometimes called a “good cancer” to get — even by some physicians. “Almost everyone I take care of has heard that,” Dr. Lieb says. “But I take issue with it. Physicians can feel very bad telling people they have cancer, and rather than saying ‘[You have cancer but] your prognosis is good,’ some downplay the diagnosis. But there isn’t a good cancer.”

Patients “need to know that cancer changes your life,” he says. “You have to take thyroid hormones. You may have to take radioactive iodine treatment, which can have side effects. You may need to have surgery, which isn’t fun. And you have to have regular testing, like ultrasounds, which increases anxiety and healthcare costs.”

And then there is the fear of recurrence, though it rarely happens with thyroid cancer. “There are surveys done with people who have thyroid cancer that show even those who are at low risk for recurrence worry they will die of thyroid cancer, or that another family member will get it,” Dr. Lieb says. “But that’s not likely.”

Where Can I Find Thyroid Cancer Support?

Your biggest sources of support can be your friends and family. Consider taking a trusted friend or relative to your appointments to take notes and ask questions you might not think of right away.

Additionally, hospitals will often have information on support groups in your area — both virtual and IRL (in real life). The doctor(s) treating your cancer may also be able to suggest some of these.

The Thyroid Cancer Survivors’ Association has information and support for both newly diagnosed people and those who have been on their cancer journey for longer.

You can also visit and join the American Cancer Society’s Cancer Survivors Network.

Fast Facts About Thyroid Cancer

  • Thyroid nodules are common as we age, and most are benign.
  • By age 80, 90% of people have at least one thyroid nodule.
  • Two-thirds of thyroid cancers occur in people under the age of 55.
  • Thyroid cancer affects three times as many women as men.
  • The two most common types of thyroid cancer — papillary and follicular — account for 95% of cases.
  • The age at which a person is diagnosed with thyroid cancer is a well-established factor in predicting survival, with older patients tending to experience more aggressive cancers.
  • Up to 25% of medullary thyroid cancer diagnoses are inherited.
  • Approximately 1.2 percent of all men and women will be diagnosed with thyroid cancer during the course of their lifetime.

Thyroid Cancer FAQs

How do I choose a thyroid surgeon?

A high-volume surgeon is best. Whether you opt for a general, endocrine, or head and neck surgeon, you want to choose a provider who does a lot of these surgeries every year, says Dr. Lieb. Dr. Chen says a good volume to shoot for is 100 per year or more.

You can find directories of qualified surgeons at the American Association of Endocrine Surgeons or the American Academy of Otolaryngology – Head and Neck Surgery.

Are there complementary therapies I can try?

While there are no great studies showing that complementary and alternative medicine can cure or treat thyroid cancer, you might find some of them helpful for relieving stress, such as aromatherapy or massage therapy.

Ask your doctor before taking any herbal supplements, and if you are already taking some, be sure to let your provider know what and how much, as some herbs can impact thyroid function or interfere with medications.

Will I be cared for mainly by one provider, or will there be multiple ones?

Thyroid cancer care is a team sport. Dr. Lieb says you can expect to be cared for by many people during your cancer treatment, including your primary care physician, your endocrinologist, and your surgeon. There will also be pathologists and social workers. Depending on the type of thyroid cancer, you may also see a nuclear medicine team, vascular surgeon, voice specialist, and imaging professionals.

What other (non-health-related) issues might I encounter during treatment?

Cancer can be expensive. Dr. Lieb says that young adults with thyroid cancer have one of the highest rates of healthcare-related bankruptcy. This is partly due to the cost of imaging studies. Another factor is that many people only have insurance through their workplace and cancer treatment can impact your ability to work. Be sure you have support to help you examine medical bills and proactively engage with your insurance provider.


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