Thyroid Cancer

Thyroid cancer is a cancer that begins in the thyroid gland, one of the largest endocrine * glands in the human body.

What Is the Thyroid Gland?

The thyroid gland is a large, butterfly-shaped gland that regulates the endocrine system. It is located in the front of the throat, just below the Adam's apple. Normally, the thyroid cannot be seen or felt under the skin.

The thyroid gland has two kinds of cells: follicular cells and parafollicular cells, also called C cells. The follicular cells make thyroid hormones (T3 and T4), and the C cells make another hormone called calcitonin, which is involved with the regulation of calcium in the blood. The pituitary * gland, which is located in the brain, releases TSH, or thyroid-stimulating hormone * . This hormone stimulates the follicular and C cells in the thyroid to create important hormones for the rest of the body. These hormones control factors that are regulated by metabolism, such as heart rate, blood pressure, body temperature, and energy consumption.

What Is Thyroid Cancer?

To understand thyroid cancer * , it is important to understand what cancer is. Cancer occurs when the cells in a certain part of the body undergo abnormal changes and start dividing without control or order, forming tumors * . A tumor found on the thyroid is called a nodule. Nodules are usually felt under the skin by the patient or by a doctor during a routine exam. Sometimes, nodules can cause neck pain or a change in voice.

There are about 37,000 new cases of thyroid cancer every year in the United States. It is much more common in women than in men. Up to 95 percent of thyroid nodules are noncancerous, or benign * , but a small percentage are cancerous, or malignant * . If detected early, thyroid cancer treatment is usually very successful. Thyroid cancer is one of the least deadly cancers.

Thyroid cancers

Thyroid cancers
Table by GGS Creative Resources. © 2016 Cengage Learning®.

What Are The Three Types of Thyroid Cancer?

There are three types of thyroid cancer:

Did You Know?

Over 95 percent of all thyroid nodules are benign. Most people who are diagnosed with thyroid cancer have an excellent prognosis. The 5-year survival rate for thyroid cancer is about 97 percent.

What Are the Symptoms of Thyroid Cancer?

Sometimes, people who have thyroid cancer may not even know that there is anything wrong. Over time, nodules may grow bigger. The vast majority of cases are detected when a patient feels a nodule in the neck. Most of these nodules (95 percent) are benign. Once thyroid cancer progresses, it may cause a variety of symptoms. These may include a change in voice, a lump on the thyroid that can be felt in the neck, enlarged lymph nodes * , pain or discomfort in the neck or ears, frequent coughing, or difficulty eating, swallowing, or breathing.

What Causes Thyroid Cancer?

As of 2015, scientists had not pinpointed what exactly causes thyroid cancer. There are, however, several known risk factors. These include the following:

How Is Thyroid Cancer Diagnosed?

Most thyroid cancers are detected when a patient or doctor feels nodules on the front of the neck. The doctor may request further testing to determine exactly what the nodule is. After nodules are found, patients are usually referred to a specialist called an endocrinologist * , who will do the following:

What Are the Stages of Thyroid Cancer?

Using some of the same tests that are used during diagnosis, doctors are able to assign a stage to thyroid cancer. Staging is used to give patients a treatment plan and prognosis. There is a standard staging system that is used for all types of cancer called TNM. T refers to the size of the tumor and whether it has spread to nearby areas. N describes how much the tumor has spread to areas such as the lymph nodes. M indicates whether the cancer has spread to other major body organs, such as the lungs or brain.

The American Cancer Society uses the following chart on its website to explain the complex staging system for thyroid cancer.

T categories for thyroid cancer:

For anaplastic thyroid cancers:

N categories for thyroid cancer:

M categories for thyroid cancer:

By considering several specific aspects of TNM, a patient's age, and the type of thyroid cancer the individual has, doctors can assign a stage from I (1) through IV (4). As with most types of cancer, those that are detected in early stages before they have spread have a better prognosis.

How Is Thyroid Cancer Treated?

Once a diagnosis of thyroid cancer has been made, patients undergo a series of procedures. In order to get rid of the cancer, doctors must get rid of all of the cells that have been affected by the cancer. Doing so almost always includes the removal of the thyroid gland, which is called a thyroidectomy. Sometimes, doctors also remove nearby lymph nodes.

A few weeks after the thyroid has been removed surgically, patients may also be given treatment with radioactive iodine to destroy any remaining tissue of the thyroid that may have cancerous cells.

If thyroid cancer is diagnosed as advanced, patients may need to undergo chemotherapy * or radiation therapy.

Because the thyroid produces important hormones that the body needs to function properly, patients who undergo a thyroidectomy are placed on hormone replacement therapy for the rest of their lives.

What Is the Prognosis for Thyroid Cancer?

Patients who are diagnosed with thyroid cancer are usually given an excellent prognosis. If treated quickly and appropriately, most cases of thyroid cancer have more than a 97 percent treatment success rate.

See also Cancer: Overview • Thyroid Disease


Books and Articles

Mulcahy, Nick. “Rise of Thyroid Cancer Is Oversimplified.” Medscape, February 21, 2014. (accessed November 17, 2015).


American Association of Endocrine Surgeons. “Thyroid Cancer: Papillary Thyroid Cancer (PTC).” Patient Education. (accessed November 17, 2015).

MedlinePlus. “Thyroid Cancer.” U.S. National Library of Medicine. (accessed November 17, 2015).


American Cancer Society. 250 Williams St. NW, Atlanta, GA 30303. Toll-free: 800-227-2345. Website: (accessed November 17, 2015).

American Thyroid Association. 6066 Leesburg Pike, Ste. 550, Falls Church, VA 22041. Telephone: 703-998-8890. Website: (accessed November 17, 2015).

National Cancer Institute. 9609 Medical Center Dr., Building 9609, MSC 9760, Bethesda, MD 20892-9760. Toll-free: 800-4- CANCER. Website: (accessed November 17, 2015).

ThyCa: Thyroid Cancer Survivors’ Association. PO Box 1545, New York, NY 10159-1545. Toll-free: 877-588-7904. Website: (accessed November 17, 2015).

* endocrine (EN-do-krin) refers to a group of glands, such as the thyroid, adrenal, and pituitary glands, and the hormones they produce. The endocrine glands secrete their hormones into the bloodstream, and the hormones travel to the cells that have receptors for them. Certain hormones have effects on mood and sometimes cause emotional swings.

* pituitary (pih-TOO-ih-tare-e) is a small oval-shaped gland at the base of the skull that produces several hormones—substances that affect various body functions, including growth.

* hormone is a chemical substance that is produced by a gland and sent into the bloodstream carrying messages that have certain effects on other parts of the body.

* cancer is a condition characterized by abnormal overgrowth of certain cells, which may be fatal.

* tumors (TOO-morz) are abnormal growths of body tissue that have no known cause or physiologic purpose. Tumors may or may not be cancerous.

* benign (be-NINE) refers to a condition that is not cancerous or serious and will probably improve, go away, or not get worse.

* malignant (ma-LIG-nant) refers to a condition that is severe and progressively worsening.

* lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.

* genes (JEENS) are chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.

* endocrinologist (en-do-krin-OLo-jist) is a doctor who specializes in treating patients with hormone-related disorders.

* ultrasound, also called a sonogram, is a diagnostic test in which sound waves passing through the body create images on a computer screen.

* biopsy (BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.

* aspiration (as-puh-RAY-shun) is the sucking of fluid or other material out of the body, such as the removal of a sample of joint fluid through a needle inserted into the joint.

* chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.

  This information is not a tool for self-diagnosis or a substitute for professional care.