Thyroid cancer occurs when the cells in the thyroid gland begin to grow abnormally into a malignant tumor. Approximately 1.2% of people will be diagnosed with thyroid cancer in their lifetime, according to the CDC. In some cases, this cancer results from exposure to radiation as a child. In contrast, hereditary thyroid cancer (HTC) occurs when a person has a genetic change (mutation) that causes their cells to be more likely to become cancerous. The mutation can be passed through generations in a family. People with HTC have a higher risk of developing thyroid cancer, and sometimes other cancers or health problems, as well.

Our genes, or DNA, tell the cells in our body how to work correctly. Cancer-risk genes are genes that can impact whether a cell will begin to grow uncontrollably into cancer. We have two copies of every gene, one from our mother and the other from our father. Hereditary thyroid cancer is most commonly inherited in an autosomal dominant way. For dominant conditions, having only one copy of a gene mutation is enough to cause symptoms. In the case of HTC, having one mutation leads to an increased risk for cancer. If a person has a mutation in one gene for HTC, there is a 50% risk that each of their children will inherit this mutation. Siblings, parents, and potentially other relatives could also have the mutation. Importantly, not everyone who has a mutation in a cancer-risk gene will develop cancer, but their chances are higher. While rare, it is possible for a person to have a mutation for a dominant condition that is absent from both of their parents. In this situation, the mutation arose early before they were conceived or born. This is called de novo inheritance. Even after de novo inheritance, if a person has a mutation in one gene for hereditary thyroid cancer, each of their children will have a 50% risk to inherit the mutation.

Hereditary thyroid cancer syndromes are conditions that impact other areas of an individual’s body in addition to increasing the risk for thyroid cancer. A syndrome can be inherited in a dominant, de novo, or recessive manner. Several examples are listed below:

 Li-Fraumeni syndrome (LFS)

Li-Fraumeni syndrome is caused by a mutation in the TP53 gene. People with LFS have up to a 78% lifetime risk for cancer. Many kinds of cancer can occur in LFS, and more than one type can arise in a single person. Non-medullary thyroid cancer has been reported in some families affected by Li-Fraumeni syndrome. It is important to diagnose LFS, because exposure to radiation therapy raises the cancer risk even further. LFS is a dominant condition, in that having only one mutation in the TP53 gene is enough to cause the syndrome

 Multiple Endocrine Neoplasia Type 2 (MEN2)

 Dominant mutations in the RET gene cause MEN2. People with this condition are at a higher risk to develop pheochromocytomas and medullary carcinoma of the thyroid, as well as parathyroid disease. The risk for medullary thyroid carcinoma in people with a RET mutation approaches 100%. For MEN2, knowing the specific mutation in a person can help determine the type of MEN2 they have, along with their type’s specific risks and related health problems.

Cowden syndrome (CS)

 People with Cowden syndrome often have large heads (macrocephaly) and are at an increased risk for different types of benign and malignant tumors, including endometrial, thyroid, and breast cancer. CS is caused by a mutation in the PTEN gene. The lifetime risk for thyroid cancer in women with Cowden syndrome is approximately 35%

What are the potential benefits for my patient? Patients identified with hereditary thyroid cancer can benefit from increased surveillance and preventative steps to better manage their risk for cancer or other clinical manifestations. Also, your patient’s family members can be tested to help define their risk. If a pathogenic variant is identified in your patient, close relatives (children, siblings, parents) could have as high as a 50% risk to also be at increased risk.


 A positive result means that a genetic mutation causing an increased risk for thyroid cancer was identified. Your risk for other cancers or health conditions may also be increased, depending on the gene involved. Your doctor can use this information to customize your care, which could include increased screening, preventative surgery, medication, and other steps. A positive result is also important for your family. Your parents, siblings, and children could have as high as a 50% chance to also have the mutation. As a result, sharing your genetic testing results with your relatives is important for their health



A negative result indicates that a genetic mutation was not identified. A negative result may indicate that there is not a cancer-risk gene mutation in you or your family. However, it can also mean that the gene increasing risk in you or your family was not included on the ordered test, or that it has not been discovered yet by scientists. Your doctor can use a negative result to continue your treatment and screening based on your clinical and family history, or they may consider another type of genetic testing.



The third possible test result is called a Variant of Uncertain Clinical Significance. A gene variant is a genetic difference that could be disease-causing (mutation) or could be a normal finding (benign). More research is needed to determine whether the variant is important or not, and it should be treated as a negative result until more information is available.

  • swollen glands in the neck
  • unexplained hoarseness that does not get better after a few weeks
  • a sore throat that does not get better
  • pain in your neck
  • difficulty swallowing
  • difficulty breathing