Genetic testing for thyroid cancer may be appropriate if you have a family history of thyroid cancer or certain other factors that may raise your risk and make you a candidate for early intervention.

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Genetic testing can often identify individuals who may have an elevated risk for thyroid cancer. Genetic testing may also help guide treatment decisions or determine whether the surgical removal of thyroid nodules is necessary.

The tests themselves are simple, but it’s important to know how the test results will be analyzed and used to counsel you. Genetic testing for thyroid cancer may help you and your healthcare team make some important decisions about monitoring and treating your thyroid and understanding your risk for thyroid cancer and other types of cancer.

Learn more about thyroid cancer.

Several different types of genetic tests for thyroid cancer. The specific test your doctor recommends will be based on the specific tumor and the type of suspected mutation.

Among the most common types of thyroid cancer genetic tests are:

  • fluorescence in situ hybridization (FISH)
  • multiplex ligation-dependent probe amplification (MLPA)
  • next generation sequencing
  • polymerase chain reaction (PCR)
  • Sanger dideoxy sequencing

Genetic testing is usually done by analyzing a sample of blood or saliva or cells taken from a swab of the inner cheek. The samples are sent to a lab, and results are usually available in 2–3 weeks.

Prior to giving a sample, you’ll likely meet with a genetic counselor or other medical professional to talk about the benefits and limits of testing, what will happen next based on your results, and what kind of services or counseling will be available after your results are received.

Much of this information and other topics are covered in “informed consent” documents that you must sign before testing is performed.

Several different genetic mutations may be detected in thyroid tumors. Some of the more common include mutations of the following genes:

Genetic testing is recommended for people who have at least two first-degree relatives — parents or siblings — diagnosed with thyroid cancer or who have a neck mass that has grown quickly. Both of these circumstances suggest that a person may have an elevated risk of thyroid cancer.

If you know you have an increased risk of thyroid cancer, you can make sure you have your thyroid checked routinely in order to detect any early signs of cancer when it’s still highly treatable.

You may also be a good candidate for genetic testing if a fine-needle biopsy of suspicious thyroid cells turns up inconclusive results. In many of these cases, the thyroid lobe that contains a suspicious nodule is removed surgically. However, an analysis of the nodule reveals that no cancer is present.

A 2019 study in JAMA Oncology suggests that certain genetic testing may be helpful in identifying biopsy samples that are benign rather than cancerous.

Risk factors for thyroid cancer fall into two categories: those you can control and those you can’t.

Of the risk factors you can influence, some of the more common include having overweight or obesity, which are associated with higher risks of many cancers. Another risk factor is iodine in the diet. Too much iodine can raise the risk of papillary thyroid cancer, while iodine deficiency may raise the risk of follicular thyroid cancer.

Thyroid cancer risk factors that are beyond your control include:

  • Age: People assigned female at birth are more likely to be diagnosed in their 40s or 50s, while people assigned male at birth are usually in their 60s or 70s when diagnosed.
  • Cowden disease: This disorder can lead to numerous thyroid problems and other health concerns.
  • Family history of thyroid cancer: A family history of thyroid cancer, especially medullary thyroid cancers that stem from a mutation of the RET gene, increases your risk.
  • Sex: People assigned female at birth are about three times as likely as people assigned male at birth to develop thyroid cancer.
  • Radiation exposure: Exposure to radiation, particularly head and neck radiation treatments administered in childhood, can raise the risk of thyroid cancer. Radiation exposure in adulthood for cancer treatments, imaging, and other causes is less likely to raise thyroid cancer risk.

Because thyroid cancer can often be detected early and treated successfully, the prognosis is usually encouraging for people diagnosed with the disease. The 5-year survival rate for most types of thyroid cancer, excluding the rare anaplastic thyroid cancer, is about 99% when the cancer is still localized, according to the American Cancer Society.

If the cancer spreads to nearby structures — known as regional cancer — the survival rate only drops slightly. Anaplastic thyroid cancer survival rates are significantly lower than those associated with more common thyroid cancers.

Genetic testing for thyroid cancer isn’t appropriate for everyone. But if thyroid cancer runs in your family or you have other risk factors, you should talk with your doctor or a genetic counselor about whether testing is right for you.

Understand that even if you have a genetic mutation associated with an elevated risk of thyroid cancer, it doesn’t mean you’ll necessarily develop the disease. But having more information to make proactive medical decisions is always a good idea.