Cancer causes cells to grow uncontrolled in your body. Cancers are named for the part of the body where they start. Thyroid cancer is cancer that begins in the thyroid gland.

The thyroid is a small, butterfly-shaped gland at the base of the throat. It is part of the endocrine system, the body system that produces hormones to regulate the body’s functions.

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Illustration by Sophia Smith

The thyroid makes the hormone thyroxine, which helps the body regulate:

  • metabolism
  • blood pressure
  • heart rate
  • body temperature
  • body weight

When thyroid cancer develops, the abnormal cancer cells can crowd out normal cells. They can also spread to other parts of the body.

The American Cancer Society (ACS) estimates that about 43,800 new cases of thyroid cancer will be diagnosed in 2022.

While thyroid cancer can affect anyone, it occurs in women almost three times more than men. In fact, it is the fifth most common cancer found in women globally and in the United States.

Factors including overexposure to radiation can impact your risk for thyroid cancer. For example, when Chernobyl experienced its nuclear-reactor accident in 1986, there was a dramatic increase in thyroid cancer, especially in young children of the area. Similar events occurred after the atomic bomb explosion in Hiroshima. Frequent radiation exposure through radiation therapy or X-rays, especially in childhood, is considered a risk factor.

Keep reading to learn a bit more about thyroid cancer.

Thyroid cancer can mimic other diseases and ailments.

Symptoms of thyroid cancer can include:

A risk factor indicates that a person with certain characteristics or medical history may have a greater chance of getting a specific disease. Some risk factors can be changed, while others cannot. But just because you have one or several risk factors doesn’t mean you will inevitably get the disease they are associated with.

Risk factors associated with thyroid cancer can include:

  • being a woman
  • having a family history of thyroid cancer
  • having a hereditary condition, such as Cowden disease or familial adenomatous polyposis
  • being overexposed to radiation in childhood, such as through X-rays or radiation therapy
  • being overexposed to pesticides
  • being overweight or having obesity

A 2015 review found that having a diet higher in iodine, fish, and seafood in iodine-deficient populations may lead to a small reduction in your risk for thyroid cancer. Excess iodine may also be linked to thyroid cancer risk. However, more research is needed to understand the role of iodine in the development of thyroid cancer.

Genetics may be the cause of thyroid cancer in an estimated 2 out of 10 people with medullary thyroid cancers.

Thyroid cancers are relatively uncommon. However, according to the ACS, thyroid cancer is one of the most rapidly increasing cancers in the United States.

The increase may be attributed to experts’ knowledge about thyroid cancer, the ability to detect the disease, and advancements in medical technology rather than because more people are getting thyroid cancer.

There are three main types of cancer, and the look of the cancer cells classifies them as:

  • differentiated, with cells appearing similar to the regular thyroid cells
  • medullary, with cells developing from our C cells, which are the cells that produce the hormone that regulates calcium and phosphate in your blood
  • anaplastic, with cells appearing different from regular thyroid cells

Types of thyroid cancer can include:

Papillary cancer

Papillary thyroid cancer is a well-differentiated form of thyroid cancer. It’s the most common type of thyroid cancer. This type of cancer cell grows slowly. However, when they do grow, they can spread to lymph nodes.

Papillary cancer is often treated successfully and has a low rate of mortality.

Follicular thyroid cancer

Follicular thyroid cancer (FTC) is the second most common type of differentiated thyroid cancer.

There tends to be a higher rate of FTC in places where people eat a diet deficient in iodine. A lack of iodine may be related to certain types of thyroid cancer, including FTC, but more research is needed to confirm this.

Like papillary cancer, FTC has a good outlook, even though it can spread to other parts of the body when untreated.

Hurthle cell cancer

Hurthle cell thyroid carcinoma accounts for 5 percent of all thyroid cancer diagnoses. It is a type of follicular thyroid cancer and can be more aggressive than other types. It also has a greater chance of metastasizing or spreading to other parts of the body.

Factors like age, tumor size at diagnosis, cancer stage at diagnosis, and sex may affect the outlook for people with Hurthle cell cancer.

Sporadic medullary thyroid cancer

Sporadic medullary thyroid cancer (MTC) comes from the C cells of your thyroid gland. These cells make a hormone that controls the amount of calcium in your blood.

Between 75 and 85 percent of medullary thyroid cancers are sporadic, meaning they aren’t hereditary. Sporadic medullary thyroid cancer occurs mainly in older adults.

If diagnosed in stages I through III, MTC can have a good outlook.

Familial medullary thyroid cancer

This type of medullary thyroid cancer is hereditary and runs in families. It can affect both children and adults.

Anaplastic thyroid cancer

Anaplastic thyroid cancer is the most aggressive form of thyroid cancer. It is undifferentiated, which means that the cells do not look like normal thyroid gland cells.

While rare, this type of cancer can also metastasize to distant locations in the body. Because it spreads fast, it may not be diagnosed until it has already spread. This can make treating it more difficult. All anaplastic thyroid cancers are considered stage IV.

Thyroid lymphoma

This is a rare type of thyroid cancer. It begins in the white blood cells located within the thyroid gland.

Thyroid lymphoma can occur frequently in people with Hashimoto’s thyroiditis, a chronic autoimmune disease that damages the thyroid.

In general, thyroid lymphoma may have a good outlook. Factors that can influence outlook may include age, tumor size at diagnosis, stage, and treatment type.

The results of a physical exam or laboratory test can reveal the presence of thyroid cancer. For example, an examination of the neck may show a small or large mass in the thyroid. Lymph nodes may also enlarge and become detected.

Lab tests and procedures used to diagnose thyroid cancer include:

  • Fine needle or core biopsy. During a biopsy, a doctor removes cells from the thyroid to test for cancer. This can help identify the type of cancer.
  • Thyroid function tests. These blood tests measure thyroid hormone levels.
  • Thyroid ultrasound. An ultrasound uses sound waves show images of the thyroid gland, particularly to examine any suspicious nodules as well as any locations the cancer may have spread.
  • CT and MRI scans. These imaging tests may be done to take a close look at any areas where the thyroid cancer may have spread.
  • Thyroid scan. This imaging test uses a small amount of radioactive iodine to test your thyroid function.

Treatment will depend on what type of cancer you have, tumor size, and if it has metastasized or spread.


Removing part or all of your thyroid is the preferred treatment for cancer tumors measuring 1 to 4 centimeters. If any lymph nodes are affected, doctors may remove them also.

The procedure may affect your body’s ability to produce thyroid hormones. If that’s the case, oral supplements can replace thyroid hormones.

A laryngoscopy may be performed after surgery to ensure your vocal cords are working as they should.

Radioiodine therapy

Your thyroid gland absorbs almost all of the iodine in your body. So, by taking in radioactive iodine, doctors may use this thyroid function to kill cancer cells.

Doctors may use radioiodine therapy after surgery to destroy any thyroid tissue left after the procedure or to treat thyroid cancer that has spread to your lymph nodes.

External beam radiation therapy

Using external radiation waves targeted at the thyroid gland can destroy cancer cells. Doctors use this type of therapy primarily in medullary and anaplastic thyroid cancers.


Chemotherapy is a drug injected into your vein or taken orally to fight cancer cells. Doctors may add this to your treatment along with radiation for those diagnosed with anaplastic thyroid cancer.

Targeted drug therapy

Advancements in medicine have led scientists to develop newer drugs that can target the changes inside cells that cause them to become cancerous.

The drugs are also known as kinase inhibitors. They can help discourage the protein kinase from telling other cells how to grow. The drugs can also block tumors from forming the new blood vessels that they need to grow.

Even if you have surgery to remove your thyroid gland, you will likely still need treatment. The doctor will look at the risk that the cancer may come back and the potential effects it had or still has on your body.

Specific treatments, such as radioiodine ablation therapy and chemotherapy, may also cause side effects.

Also, if your thyroid gland is removed, you will likely need to take medication daily to replace the hormones your thyroid gland was responsible for. This medication, called levothyroxine (Synthroid, Levoxyl, Tirosint, and others), helps maintain your metabolism while preventing the reoccurrence of cancer.

People diagnosed in the early stages of thyroid cancer generally respond well to treatment and go into remission. Some types of thyroid cancer have a higher rate of returning, or recurring, than others.

Thyroid cancer has a 95 percent 5-year survival rate. This statistic means that 95 percent of people diagnosed with thyroid cancer will be alive 5 years after diagnosis.

More specific survival rates depend on age, the size and cell type of the tumor, how fast it is growing, and if it has spread to other parts of the body.

In most cases, the cause of thyroid cancer isn’t known, which means that there’s no known way to prevent it for many people.

Medullary thyroid cancer can be hereditary, so it’s best to talk to a doctor if your family has a history of this type of thyroid cancer. The doctor can refer you to a genetic counselor who can determine how likely you are to develop thyroid cancer.

There are many different forms of thyroid cancer. They’re classified by type of cancer cell.

Although you can’t prevent thyroid cancer, most types are treatable. Doctors will often remove all or part of the thyroid gland and use targeted therapies to kill any remaining cancer cells.

Post-surgery, you may still require regular follow-up visits with your doctor to monitor any signs that the cancer might come back or recur.