Thyroid Cancer Screening

Thyroid cancer is a disease in which malignant (cancer) cells form in the tissues of the thyroid gland.

The thyroid is a gland at the base of the throat near the trachea (windpipe). It is shaped like a butterfly, with a right lobe and a left lobe. The isthmus, a thin piece of tissue, connects the two lobes. A healthy thyroid is about the size of a walnut. It usually cannot be felt through the skin.

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Anatomy of the thyroid and parathyroid glands. The thyroid gland lies at the base of the throat near the trachea. It is shaped like a butterfly, with the right lobe and left lobe connected by a thin piece of tissue called the isthmus. The parathyroid glands are four pea-sized organs found in the neck near the thyroid. The thyroid and parathyroid glands make hormones.

The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones. Thyroid hormones do the following:

• Control heart rate, body temperature, and how quickly food is changed into energy (metabolism).
• Control the amount of calcium in the blood.

For more information about thyroid cancer, see Thyroid Cancer Treatment.

Thyroid cancer is found more often in women.

Thyroid cancer is most often diagnosed in men and women aged 45 to 64 years. It is the most commonly diagnosed cancer in women aged 20 to 34 years. Women are about three times more likely than men to have thyroid cancer.

The number of people diagnosed with thyroid cancer in the United States had been rising for at least 40 years, but the number of deaths from thyroid cancer has stayed the same or decreased slightly. The rise in rates of thyroid cancer appears to be leveling off in recent years, and there is a decrease in the rate of thyroid tumors less than 1 centimeter in size. Most cases of thyroid cancer respond to treatment and are usually cured.

Being exposed to radiation increases the risk of thyroid cancer.

Anything that increases a person's chance of getting a disease is called a risk factor. Not every person with one or more of these risk factors will develop thyroid cancer, and it will also develop in people who don't have any known risk factors. Talk with your doctor if you think you may be at risk.

Risk factors for thyroid cancer include the following:

• Being exposed to radiation to the head and neck as an infant or child or being exposed to radiation from an atomic bomb. The cancer may occur as soon as 5 years after exposure.
• Having a family history of thyroid disease or thyroid cancer.
• Having a history of goiter (enlarged thyroid).
• Having a genetic condition such as multiple endocrine neoplasia type 2 syndrome (MEN2), which is caused by a change in the RET gene.
• Being female.
• Being Asian.

Tests are used to screen for different types of cancer when a person does not have symptoms.

Scientists study screening tests to find those with the fewest harms and most benefits. Cancer screening trials also are meant to show whether early detection (finding cancer before it causes symptoms) helps a person live longer or decreases a person's chance of dying from the disease. For some types of cancer, the chance of recovery is better if the disease is found and treated at an early stage.

There is no standard or routine screening test for thyroid cancer.

There is no standard or routine screening test used for early detection of thyroid cancer. Thyroid cancer that does not cause symptoms may be found during the following:

• A routine physical exam when the doctor checks the patient's neck for lumps (nodules) or swelling in the neck, voice box, and lymph nodes, or anything else that seems unusual.
• Surgery that is done for another condition.
• An ultrasound that is done for another condition.

Screening for thyroid cancer may not help the patient live longer.

Studies have shown that screening for thyroid cancer does not decrease the chance of dying from the disease. No randomized clinical trials have been done in the United States to find out if a neck exam, ultrasound, or other screening test decreases the risk of dying from thyroid cancer. Neck exams and ultrasound are sometimes used to screen for thyroid cancer but do not decrease the risk of dying from the disease.

Screening tests for thyroid cancer are being studied in clinical trials.

Information about clinical trials supported by NCI can be found on NCI’s clinical trials search webpage. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.

Screening tests have risks.

Decisions about screening tests can be difficult. Not all screening tests are helpful and most have risks. Before having any screening test, you may want to discuss the test with your doctor. It is important to know the risks of the test and whether it has been proven to reduce the risk of dying from cancer.

The risks of thyroid cancer screening include the following:

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This PDQ cancer information summary has current information about the screening of thyroid cancer. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.

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PDQ® Screening and Prevention Editorial Board. PDQ Thyroid Cancer Screening. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/thyroid/patient/thyroid-screening-pdq. Accessed <MM/DD/YYYY>.

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