What Is Thyroid Cancer? Symptoms, Causes, Diagnosis, Treatment, and Prevention
CancerThyroid Cancer

What Is Thyroid Cancer?

What Is Thyroid Cancer?
Everyday Health
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Updated on May 29, 2026
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Thyroid cancer is a type of cancer that starts in the thyroid gland, a small, bilobed butterfly-shaped gland located at the base of the neck. It develops when abnormal cells in the thyroid grow and multiply, forming a tumor.

Many forms of thyroid cancer are highly treatable, especially when caught early, though treatment and outlook vary depending on the type and stage of the disease. Some people may need surgery, radiation, medication, or ongoing monitoring as part of long-term care.

Types of Thyroid Cancer

There are three main types of thyroid cancer, according to the American Cancer Society.

Differentiated

This category includes papillary, follicular, and oncocytic (also called Hürthle cell ) carcinoma. Papillary and follicular carcinoma both develop in thyroid follicular cells. Unlike anaplastic and medullary carcinoma, differentiated thyroid cancer cells can look like normal thyroid cells when viewed under a microscope.

Differentiated thyroid cancer is the most common type of thyroid cancer, with papillary carcinoma accounting for about 80 percent of thyroid cancer cases, and follicular carcinoma accounting for about 10 percent.

Papillary carcinoma grows very slowly, typically only in one lobe of the thyroid gland. They often spread to the neck’s lymph nodes over time. Despite this spreading, however, they are usually easily treated and are rarely fatal.

Follicular carcinoma may spread to other parts of the body, such as the lungs and bones, rather than the lymph nodes alone. The outlook for follicular thyroid cancer is worse than for papillary carcinoma, but is still quite good overall.

Anaplastic Carcinoma

Anaplastic carcinoma, though rare — it makes up only 1–2 percent of thyroid cancers — is the most aggressive type of thyroid cancer. It often produces symptoms early and spreads to other parts of the body and is difficult to treat. All anaplastic thyroid cancers are considered stage 4 disease, and up to 50 percent will have metastatic disease in other organs by the time it’s discovered.

The outlook is the worst for anaplastic thyroid carcinoma. While the five-year survival rate for differentiated cancer usually exceeds 95 percent, for anaplastic thyroid carcinoma, the five-year survival rate is below 10 percent even with the best treatment.

Medullary Carcinoma

Medullary thyroid carcinoma (MTC) is a less-common type of thyroid cancer that develops in the thyroid’s C cells, which produce the hormone calcitonin. It occurs in 2 to 4 percent of all thyroid cancers. Unlike papillary and follicular thyroid cancers, MTC does not arise from the follicular cells that make thyroid hormone. Some cases occur sporadically, while others are inherited through genetic syndromes passed down in families. Medullary thyroid carcinoma has an excellent long-term prognosis with treatment.

Thyroid Cancer Signs and Symptoms

Thyroid cancer affects the thyroid gland, which is located in the neck and releases hormones that help regulate metabolism, growth, and maturation. Most diagnosed thyroid cancers do not produce any signs or symptoms.

Thyroid cancer is sometimes found during a routine checkup, in the form of a nodule. It may also be found in an ultrasound, a CT scan, or via other procedures conducted for different health issues.

A lump in the neck, which you may or may not feel, may be the only sign of thyroid cancer. Other symptoms of thyroid cancer may include:

  • Neck swelling
  • Difficulty swallowing
  • Pain in the front of the neck,
  • Hoarseness or voice changes

These symptoms may occur at later stages, as a thyroid tumor grows larger. It’s also important to note that other conditions may cause symptoms similar to thyroid cancer.

Causes and Risk Factors for Thyroid Cancer

Aside from age, gender, and race, other risk factors for thyroid cancer include:

  • Radiation exposure in childhood
  • Inherited conditions, such as familial adenomatous polyposis or multiple endocrine neoplasia (MEN) syndrome
  • Family history of thyroid cancer
  • History of benign thyroid nodule
  • Gender, since papillary thyroid occurs about three times more often in women than in men

How Is Thyroid Cancer Diagnosed?

As with other types of cancer, a thyroid cancer diagnosis begins with your doctor’s review of your symptoms and medical history, including a family history that may indicate a higher risk for thyroid cancer.

Your doctor will also perform a physical exam, paying special attention to the feel and size of your thyroid and the lymph nodes in your neck, where the cancer might have spread.

If thyroid cancer is suspected, your doctor or a specialist may order various tests, which can include:
  • A neck ultrasound, which can determine if a thyroid nodule or lump is fluid-filled or solid (solid nodules are more likely to be cancerous)
  • CT scans, which can show the location and size of thyroid cancers using cross-sectional X-ray images
  • Magnetic resonance imaging (MRI), which can provide highly detailed images of the thyroid
  • Positron emission tomography (PET) scans, which can show the spread of thyroid cancer in all areas of the body at once (usually performed after cancer is diagnosed)
  • Blood tests that measure the levels of certain hormones — particularly thyroid-stimulating hormone (TSH), T3, and T4 — to see how well the thyroid is functioning
  • Blood tests for cancer markers, such as elevated levels of calcitonin (a hormone produced by thyroid “C” cells), which can indicate a type of thyroid cancer called medullary carcinoma
A conclusive diagnosis of thyroid cancer can happen only after a biopsy, a procedure in which doctors remove cells and study them under a microscope. In a fine-needle aspiration biopsy, a specialist will insert a needle through your skin and into your thyroid several times to take tissue samples from different areas of the gland. A surgical biopsy, which is a more invasive procedure, may be necessary if results from a fine-needle aspiration biopsy are unclear or if additional tissue for molecular testing is needed.

Treatment and Medication Options for Thyroid Cancer

About 99 percent of people with well-differentiated thyroid cancer survive for at least five years after diagnosis.

 Part of the reason for this high survival rate is that thyroid cancer is usually caught early, and differentiated thyroid cancers are naturally quite slow growing.

There are several different treatment options for thyroid cancer. The most effective treatment will depend on the stage and type of thyroid cancer you have.

Thyroid Cancer Surgery

Surgery is often the primary treatment for differentiated thyroid cancer. If the cancer is only in one lobe of your thyroid gland, your surgeon may opt for a lobectomy.

 In this procedure, the surgeon makes an incision in your neck to expose the thyroid, then cuts out the affected lobe — often along with the strip of tissue that connects the two lobes.

The most common thyroid cancer surgery, however, is a thyroidectomy, in which the entire gland is removed.

 Your surgeon may also remove the lymph nodes in the back of your neck if your thyroid cancer has spread to them. The reason for removing the entire gland is to prevent future cancers in the remaining tissue.
Thyroid cancer surgery may cause the following side effects:

  • Temporary or permanent voice hoarseness
  • Low blood calcium levels (from damage to the nearby parathyroid glands)
  • Excessive bleeding, blood clots, or wound infections

Also, after undergoing a thyroidectomy, you will have to take daily thyroid hormone pills.

Radiation Therapy

There are two types of radiation. First is external beam radiation and the second is radio-iodine ablation. External beam radiation may be used if needed after surgery to destroy any cancer cells still left in the body. In this procedure, which is often used if the cancer has spread beyond the thyroid gland, doctors treat the area with high-energy X-rays or another type of radiation, by directing the beam to the thyroid gland.

Radiation therapy may cause the following side effects:

  • Nausea
  • Fatigue
  • Temporary skin changes (similar to a sunburn)
  • Throat issues such as trouble swallowing, dry mouth, and hoarseness
Alternatively, your doctor may use a special radiation technique called radioactive iodine (RAI) therapy. This technique makes use of the fact that the thyroid gland naturally absorbs nearly all of the iodine in your body, including radioactive forms of iodine.

When you swallow RAI capsules or fluids, your thyroid tissues — including cancer cells that have spread to other parts of the body — absorb the RAI, which destroys the cancer cells.

Possible side effects of RAI therapy include temporary:

  • Tenderness and swelling of the neck or salivary glands
  • Nausea and vomiting
  • Dry mouth and changes in taste

Medication-Based Therapies

A few different treatments for thyroid cancer involve taking medications. In thyroid hormone therapy, drugs are used to stop the body from producing thyroid-stimulating hormones. This helps slow the growth of thyroid cancer and prevent the cancer from returning after treatment.

As with other types of cancer, chemotherapy is often used to treat thyroid cancer that has spread to other areas of the body. But most chemotherapy drugs affect other rapidly dividing cells in the body that aren’t cancerous, leading to a number of side effects, including hair loss, diarrhea, and fatigue.

A newer kind of chemotherapy — targeted therapy — uses drugs that interfere with specific molecules that cancer cells need to grow, according to ACS.

Though less damaging to the body than regular chemotherapy, targeted therapy drugs may cause side effects, which range from fatigue and high blood pressure to heart and liver problems.

Complications of Thyroid Cancer

Thyroid cancer and its treatments can lead to a range of long-term health effects, particularly in patients diagnosed and treated at a young age. Some possible complications include:

  • Osteoporosis
  • High blood pressure
  • Heart rhythm disorders
  • Heart valve disease

FAQ

What is thyroid cancer?

Thyroid cancer is a type of cancer that starts in the thyroid gland, a small gland in the neck that helps regulate metabolism through hormone production. It develops when cells in the thyroid grow and divide abnormally. Over time, these cells can form a tumor.

Many people have no symptoms in the early stages of thyroid cancer. When symptoms do appear, they may include a lump in the neck, swelling, or changes in the voice. Some people may also have difficulty swallowing or discomfort in the neck.

Thyroid cancer is not ranked in the top 10 most common cancers in the United States, but diagnosis rates have increased in recent years. This is partly because imaging tests are now used more often and can detect small tumors earlier. It is one of the more treatable forms of cancer when found early.

Yes, most types of thyroid cancer are highly treatable and curable, especially when diagnosed early. Treatment often includes surgery to remove part or all of the thyroid gland. Some people may also need radioactive iodine therapy or other follow-up care.

Some people do. If the thyroid is removed, lifelong thyroid hormone replacement medication is usually needed to replace the hormones the body can no longer make or to suppress future regrowth of cancer. Ongoing monitoring is also common to check hormone levels and detect any recurrence.

Resources We Trust

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
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