What is thyroid cancer?

Thyroid cancer occurs when there is abnormal cell growth in the butterfly-shaped gland in the front of the neck called the thyroid. The thyroid produces hormones that play an important role in helping to regulate the body’s growth and the way it breaks down food and nutrition (metabolism). In some cases, thyroid cancer can spread from the thyroid to other parts of the body. 

Children with thyroid cancer usually do very well with treatment, even if the cancer has spread. When we evaluate and treat thyroid cancer, we focus on creating a care plan that fits each child’s unique situation. Our goal is to treat the cancer safely, lower the risk of side effects and help your child go on to live a healthy, full and rewarding life. 

Types of thyroid cancer in children

Thyroid cancer in children is grouped into these types:

• Papillary thyroid cancer (PTC) is the most common type of thyroid cancer found in children and teens. It makes up about 90 to 95% of all thyroid cancer cases. Teen girls are more likely to develop this type of cancer than boys or younger children. PTC usually grows slowly and often starts on one side (or lobe) of the thyroid, though it can sometimes affect both sides. It can spread to the lymph nodes in the neck and, less often, to other parts of the body like the lungs. The good news is that papillary thyroid cancer usually responds very well to treatment.
• Follicular thyroid cancer (FTC) is a less common type of thyroid cancer in children. It usually appears as a single lump, or nodule, on one side of the thyroid gland. Unlike papillary thyroid cancer, which often spreads to nearby lymph nodes, follicular thyroid cancer can spread through the bloodstream to other parts of the body, like the lungs or bones. If the cancer has not spread into nearby blood vessels, surgery to remove the affected part of the thyroid can often lead to the cancer going away altogether.
• Papillary and follicular thyroid cancers are known as differentiated thyroid cancers (DTC). This means they both start in the thyroid cells that make thyroid hormone. In most children, we don’t know exactly why DTC develops. However, certain factors can increase the risk, like exposure to radiation at a young age (especially before age 10) or having a family condition that makes some people more likely to develop tumors.

Family history of thyroid cancer

If a family member is diagnosed with papillary or follicular thyroid cancer, there is a small—but real—chance that other family members could develop the same type of cancer (genetic factors). This risk may be limited to thyroid cancer, or it may be linked to a higher chance of other cancers or thyroid-related conditions. These can include PTEN hamartoma tumor syndrome, DICER1-related tumor predisposition syndrome, and familial adenomatous polyposis, which are inherited conditions that can increase cancer risk. 

• Medullary thyroid cancer (MTC) is often inherited in children and is linked to a condition called multiple endocrine neoplasia type 2 (MEN2). It starts in special cells in the thyroid that help control calcium levels in the body. MTC can spread to the lymph nodes and other parts of the body. Because these cells do not take in iodine, treatment usually includes surgery and oral chemotherapy if the cancer spreads. Here at Children’s Hospital of Philadelphia (CHOP), we care for children with MTC through our Advanced Pediatric Thyroid Cancer Therapeutics Clinic, where we carefully follow each child’s treatment and recovery.
• High-grade follicular-derived thyroid cancer is very rare in children, making up less than 1% of all thyroid cancer cases. It is more aggressive than papillary or follicular thyroid cancers. This type of cancer can develop from papillary or follicular cancer and may spread to the lymph nodes or other parts of the body. Some of these cancers grow and spread more quickly because the cells do not look or act like normal thyroid cells; these are called poorly differentiated thyroid cancers. Like medullary thyroid cancer, poorly differentiated and high-grade thyroid cancers often do not respond to treatment with radioactive iodine. 

Signs and symptoms of thyroid cancer in children

There are often no obvious signs or symptoms for children and adolescents with thyroid cancer. In most cases, your child’s doctor will notice a lump in your child’s neck during a physical exam or through a radiology study for an unrelated issue, then determine the lump to be a thyroid nodule. 

When there are signs and symptoms, they may include: 

• A visible lump in your child’s neck
• The sensation of a lump in your child's neck when they are swallowing or lying down
• Hoarseness or another change in your child's voice 

For certain inherited forms of medullary thyroid cancer, there may be additional physical signs and features. 

Causes of thyroid cancer in children

We do not know the cause of thyroid cancer for about 90% of children who develop it. In the remaining 10% of cases, causes can include risk factors like: 

• Genetic factors that increase the possibility for certain thyroid cancer, like medullary thyroid cancer and differentiated thyroid cancer to develop. 
• Exposure to ionizing radiation in their head and neck as part of previous treatment for another form of cancer. Patients less than 10 years old at the time of exposure are at greatest risk.
• Autoimmune thyroid disease, including Hashimoto’s thyroiditis (also known as chronic lymphocytic thyroiditis). 

Testing and diagnosis of thyroid cancer

We begin diagnosing thyroid cancer by taking a complete medical history and performing a thorough physical exam, including a careful check of the thyroid and the lymph nodes in the neck. 

To help diagnose thyroid cancer, we may use several tests:

• Blood test: We check the thyroid-stimulating hormone (TSH) level to see how well your child’s thyroid is working.
• Thyroid ultrasound: This uses sound waves to create images of the thyroid. It helps us see the size, number and appearance of any nodules (lumps) or abnormal lymph nodes in your child's neck.
• Fine needle aspiration (FNA): We use a thin needle to collect cells from your child's thyroid or nearby lymph nodes. We then look at these cells under a microscope to check for cancer.
• Nuclear medicine uptake and scan: If your child’s TSH is low, we may order this test. It shows whether a thyroid nodule is absorbing more iodine than usual, which can help guide treatment.