Pediatric Thyroid Cancer

The thyroid is an important gland situated at the base of the throat. It’s responsible for a number of bodily functions, including controlling metabolism, heart rate, body temperature, and the calcium content of the blood circulation. The three hormones secreted by the thyroid (thyroxine, triiodothyronine, and calcitonin), are important for growth in children.

Cancer of the thyroid in children is not common overall but is considered the most common type of childhood cancer affecting the endocrine system. Researchers have noted that the rates of pediatric thyroid cancer have risen over the last four decades. However, this is potentially due to improvements in detection and diagnosis rather than more children developing the condition.

What Causes Pediatric Thyroid Cancer?

There are certain factors that are known to increase a child’s risk of developing thyroid cancer. These include:

• Exposure to radiation
• Certain genetic syndromes, including multiple endocrine neoplasia type 2A or type 2B
• Family history of thyroid cancer

Thyroid cancer affects girls about four to six times more often than boys.

Thyroid cancer may arise from nodules on the thyroid, though more often than not, thyroid nodules are benign and non-cancerous. About one in four to five thyroid nodules may become malignant (cancerous). This is in contrast with thyroid nodules found in adults, which are found to be malignant only 5 to 10% of the time (less than one in 10).

There are three main types of pediatric thyroid cancer depending on what type of thyroid cell the tumor develops from. Papillary thyroid carcinomas are the most common form, accounting for 80-90% of childhood thyroid cancer cases. This is followed by follicular thyroid carcinomas (making up approximately 10% of cases). Medullary thyroid carcinomas are rare and typically linked to inherited genetic conditions.

Signs and Symptoms of Childhood Thyroid Cancer

Cancerous thyroid tumors in children usually appear as a lump or mass in the neck. Other associated signs and symptoms of papillary or follicular thyroid carcinomas can include:

• Swollen lymph nodes
• A tight or full sensation in the neck
• Difficulty breathing
• Difficulty swallowing
• Hoarseness or change in the voice

Additional symptoms associated with medullary thyroid cancer include:

• Painless bumps on the lips, tongue, or eyelids
• Lack of tear production
• Constipation

Diagnosis and Treatment

Investigation and management of thyroid cancer or suspicious thyroid nodules are performed by an otolaryngologist (ear, nose, throat specialist) or head and neck surgeon.

When investigating a diagnosis of thyroid cancer, the doctor will perform or order a variety of tests. These tests both diagnose as well as determine the stage of cancer, which identifies how far the cancerous cells may have spread throughout the body. Creating a fuller picture of the stage of cancer allows the surgeon to plan the most appropriate treatment.

Tests and procedures involved in investigating pediatric thyroid cancer include:

• Physical exam of the body
• Blood tests checking for thyroid function, certain proteins, or certain genes
• Imaging scans, including ultrasounds, CT, X-ray, and MRI scans
• Fine-needle aspiration biopsy to sample thyroid cells for cancerous changes
• Surgical biopsy to remove a thyroid nodule or a whole lobe from the thyroid for evaluation if a fine-needle aspiration biopsy is inconclusive

Currently, the first-line treatment for pediatric thyroid cancer is surgery. Depending on the extent of the cancer, surgery may involve removing half the thyroid (a lobectomy), removing between half to almost all the thyroid (subtotal thyroidectomy), or removing the entire thyroid (total thyroidectomy). Subtotal or total thyroidectomy are common in children with the papillary or follicular forms of thyroid cancer, as these types tend to spread (metastasize) and the tumors are often already large at the time of diagnosis. The risk of the cancer returning is reduced if a total thyroidectomy is performed.

Radioactive iodine therapy may be recommended to destroy any residual cancerous cells in the thyroid after surgery or if surgery was not an appropriate option to remove the tumor. Chemotherapy is also used in some cases if cancerous cells have metastasized to other parts of the body.

After addressing the thyroid cancer, long-term thyroid hormone therapy may be necessary to substitute for the hormones normally produced by the thyroid.

The chance of successful treatment and survival is very good for children with papillary or follicular thyroid cancer. Younger age at time of diagnosis, smaller tumors, and cancers localized to the thyroid are associated with the best prognosis. However, once the cancer has been treated, it is possible for it to return. Malignant cells may arise again in the thyroid (if the thyroid hadn’t been entirely removed), or in another area of the body. Recurrent thyroid cancers can be treated with radioactive iodine therapy or other targeted therapies.

Thyroid cancer in children is not common overall, but it is still worth being aware of your child’s risk factors. Signs that may indicate thyroid cancer, such as changes to the voice or a swelling in the neck, should be investigated by an otolaryngologist or pediatrician without delay.