Thyroid Malignancies in Children

What is pediatric thyroid cancer?

 The thyroid is a butterfly-shaped gland in the neck that produces hormones that are important for growth and a healthy metabolism. 

Pediatric thyroid cancer (thyroid carcinoma) is cancer in the thyroid gland. Thyroid gland cancers are rare childhood cancers affecting fewer than 100,000 children yearly. While thyroid cancer can happen at any age, childhood thyroid cancer is most common in the teenage years, followed by adolescents ages 15 to 19.

Thyroid cancer often appears as a lump in the front of the neck and often during a chance medical exam or by a parent. 

Thyroid cancer can spread or metastasize to other body parts such as the lymph nodes; however, it is a childhood cancer that responds well to treatment. 

Types of thyroid cancer.

Differentiated thyroid carcinomas:  papillary thyroid carcinoma and follicular thyroid carcinoma. These types of thyroid cancer develop from the thyroid gland cells that produce a thyroid hormone. 

  • Papillary carcinoma is the more common type, accounting for about 90 percent of thyroid cancers in children. 
  • Follicular carcinoma is less common and accounts for about 10 percent of cases.

Medullary thyroid carcinoma:  This is an extremely rare thyroid cancer that develops in thyroid cells that do not produce thyroid hormone.

Medullary thyroid cancer:  This is more prevalent in adults. There are familial conditions where a child develops medullary thyroid carcinoma early in childhood or infancy. 

Anaplastic thyroid cancer:  This is another extremely rare but aggressive thyroid cancer occurring almost exclusively in adults.

What causes thyroid cancer in children?

The cause of most thyroid cancers in children is unknown but linked to radiation exposure and certain genetic conditions.

What causes thyroid nodules in children?

Exposure to radiation, including radiation used to treat cancer, increases the risk of developing thyroid nodules or thyroid cancer. 

Inherited (familial) or genetic conditions may cause thyroid cancers or nodules; however, some situations occur without being present in the parents. 

What are the symptoms of thyroid cancer in children?

Most children who are diagnosed with thyroid cancer feel well at the time of diagnosis, and many have no symptoms at all. While symptoms may vary from child to child, the most common include:

  • a lump in the neck
  • swollen lymph nodes in the neck
  • a sensation of a lump in the throat when swallowing 
  • unexplained hoarseness

Remember that similar symptoms can be associated with more common medical problems and conditions. Please consult your child’s physician for a diagnosis if your child has one of these symptoms.

How is thyroid cancer diagnosed in children?

The first step in treating a child with thyroid cancer is forming an accurate and complete diagnosis. In addition to a medical history and physical exam, a physician may order several tests to diagnose thyroid cancer and determine whether it has spread.

Blood tests are used to determine if the thyroid is working properly.

Ultrasound is the best imaging technique to visualize a known or suspected thyroid nodule. Ultrasound uses sound waves to assess the location and characteristics of nodules in the thyroid gland. Because ultrasound uses only sound waves, it does not expose the patient to any harmful radiation.

Fine-needle aspiration (sometimes called a biopsy) uses a very thin needle to take a sample of a thyroid nodule and/or lymph nodes to gather information about whether the thyroid nodule may be a thyroid cancer.

Surgery is sometimes needed to determine whether a thyroid nodule is a thyroid cancer, if the result of fine-needle aspiration (biopsy) is not definitive.

Computerized tomography (CT or CAT) scan is sometimes needed to take detailed images of the neck or chest, to help determine what surgery or other treatments are needed.

Genetic testing is useful in many cases to determine whether thyroid cancer may be part of an underlying genetic condition.

How is thyroid cancer treated in children?

Components of thyroid cancer treatment in children may include the following:

Surgery is the first and most important treatment for thyroid cancer. Thoroughly and safely removing as much of the tumor as possible is important to ensure the best possible long-term outcome. This often includes removing the entire thyroid gland, and if necessary, any lymph nodes in the neck that may contain thyroid cancer. This allows your doctors to form a complete diagnosis of the cancer type and obtain information on the stage of the disease, which will help determine if any further treatments are necessary.

Radioactive iodine therapy may be recommended to destroy any remaining cancer cells after surgery. This therapy uses the natural need of thyroid cells for iodine to treat thyroid cancer cells that may remain in the body after surgery. Radioactive iodine is absorbed by and destroys these remaining thyroid cells, even if they are located in areas that cannot be removed by surgery (like the lungs). In patients with high-risk thyroid cancer, radioactive iodine therapy can improve outcomes and reduce the risk of thyroid cancer recurrence. Radioactive iodine can only be used to treat differentiated types of thyroid cancers, not medullary thyroid cancers.

Hormone therapy is used to replace normal hormones and slow the growth of cancer cells. If the entire thyroid was removed, lifelong treatment with thyroid medication is needed. In patients with high-risk thyroid cancer, giving a slight excess of thyroid medication may improve outcomes and reduce the risk of thyroid cancer recurrence.

Molecular therapies may be effective for patients with advanced differentiated thyroid carcinoma that does not respond to surgery and radioactive iodine therapy, and for patients with advanced medullary thyroid carcinoma. 

What is the long-term outlook for children with thyroid cancer?

The prognosis for children with thyroid cancer is excellent, with a long-term survival rate greater than 95 percent. Outcomes are best when thyroid cancer is detected and treated early.

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