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Compared to adults, thyroid nodules are much less common in children and adolescents. However, childhood thyroid nodules are more likely to be malignant. In some cases, pediatric thyroid cancer may have spread to nearby lymph nodes and distant sites (lung) at diagnosis. It is also more likely to recur. Despite the greater tendency for spread in children compared to adults, differentiated thyroid cancer has an excellent outcome, with greater than 95% survival rate.
Most thyroid cancers in children are differentiated thyroid cancers (DTC), which arise from follicular cells in the thyroid gland. There are two types of differentiated thyroid cancers: papillary and follicular. Approximately 90% of pediatric thyroid cancers are papillary thyroid cancer.
Papillary thyroid cancer can often present with more than one nodule and involve both lobes of the thyroid (bilateral). In many cases, it has spread outside the thyroid to regional (cervical) lymph nodes at diagnosis. Follicular thyroid cancer is usually localized in the neck but is more likely to spread to lungs and bones.
Differentiated thyroid carcinomas are iodine-avid. This means that they take up iodine. This feature is important for screening and treatment with radioactive iodine.
Differentiated thyroid cancer occurs most often in older children and teens. Adolescents are 10 times more likely to develop thyroid cancer compared to younger children. These cancers are more common in females than males. Certain genetic factors may increase risk, and the tendency to develop thyroid and other cancers may be passed down in families. Children with differentiated thyroid cancer often have gene rearrangements of the RET gene.
|Familial Adenomatous Polyposis (FAP)
|PTEN Hamartoma Tumor Syndrome
Patients treated with radiation as a medical therapy are at increased risk of developing thyroid cancer. Environmental exposure to radiation such as radioactivity from nuclear disasters also increases risk. Higher doses of radiation and younger age during exposure are associated with higher risk.
The main sign of thyroid cancer is a nodule, or lump, in the thyroid gland. Sometimes, lymph nodes in the neck will appear swollen. In rare cases, symptoms might include problems breathing, difficulty or pain swallowing, and hoarseness.
However, often thyroid cancer does not cause any symptoms and may be found as part of a routine exam.
The stage, or extent of disease, depends on whether the cancer has spread. Stage of thyroid cancer is based on the characteristics of the thyroid nodules as well as spread of disease to lymph nodes and other parts of the body (lungs).
Patients who have no spread of disease outside the neck are considered Stage I.
Patients with distant spread of disease outside the neck are considered Stage II.
Post-operative staging is used to classify patients into risk groups. For all pediatric thyroid cancer patients, the risk of death is very low. However, some patients may be at higher risk for continued disease or spread of disease (metastases) after surgery.
|Risk||Spread of disease|
|Low Risk||Cancer is only in the thyroid gland with little or no spread to lymph nodes|
|Intermediate Risk||Some spread of cancer to nearby lymph nodes|
|High Risk||Significant spread of cancer to nearby lymph nodes, invading tissues outside the thyroid, or distant spread (to lungs)|
Thyroid cancer has a >95% survival rate in pediatric patients. Recurrence is more likely in children under 10 years of age and patients who have regional lymph node involvement at diagnosis. However, even with risk of recurrence, chance of survival is very good.
Factors that influence prognosis include:
Care by a multidisciplinary pediatric team is important to manage assessment, treatment, and long-term monitoring of patients with pediatric thyroid cancer. Care decisions are focused on balancing risk of continued disease and harm due to treatment side effects. Because of the risk of recurrence and other considerations (e.g., hormone function, genetic predisposition), ongoing follow-up is needed for all patients.
Surgery to remove the thyroid gland (thyroidectomy) is the main treatment for thyroid cancer. If the tumor is small, a partial thyroidectomy may be an option. This usually involves removing a lobe and isthmus of the thyroid gland.
More often, a total thyroidectomy is recommended. Complete removal of the thyroid helps to lower the risk of continued disease and assists in follow-up care using radioactive iodine in imaging and treatment.
A thorough neck and thyroid ultrasound and fine needle aspiration of suspicious lymph nodes is used to help plan surgery. In addition to removing the thyroid nodule, the surgeon may remove lymph nodes and other tissues in the central area or sides of the neck. This procedure is called neck dissection. Surgery that is more extensive can help reduce recurrence in higher risk patients.
Surgery to remove lymph nodes in the neck is called neck dissection. Central neck dissections are typically done when the primary thyroid tumor is larger than 4 cm or when the tumor has spread beyond the tissue that covers the thyroid gland (thyroid capsule).
Lateral neck dissections are most often done when the thyroid cancer has spread to the lymph nodes in the neck. Both types of neck dissections involve removing the lymph nodes that are most likely to communicate with the thyroid gland and are most likely to contain cancer cells which have spread.
Surgery should be done by an experienced surgeon who regularly performs these procedures in children. Treatment guidelines recommend that surgery be performed by a high-volume thyroid surgeon who does at least 30 similar procedures each year. This reduces the risk of surgical complications. Risks of surgery include damage to structures in the neck region such as nerves, specifically the recurrent laryngeal nerve, and parathyroid glands.
Each person has 4 parathyroid glands, which are very small structures located behind the thyroid. These glands release parathyroid hormone, a hormone responsible for maintaining normal levels of calcium in the body. Sometimes parathyroid glands are harmed during surgery. Even in the absence of surgical damage, the parathyroid glands often get “stunned” after thyroidectomy. This results in hypo-parathyroidism, and low levels of parathyroid hormone. Patients have symptoms of low calcium (or hypocalcemia) including muscle cramps and numbness and tingling in the hands, feet, and face. Treatment requires the use of a strong form of vitamin D (calcitriol) and calcium supplementation. This condition may be temporary (“Transient post-surgical hypo-parathyroidism”) or permanent. When the parathyroid glands are removed or permanently damaged, hypo-parathyroidism may require lifelong treatment.
Another risk of thyroid surgery is injury to the recurrent laryngeal nerve. This nerve allows the vocal cords to move and function for speech. Sometimes, the recurrent laryngeal nerve may have to be removed due to the tumor itself.
Before surgery, otolaryngologists typically perform a “scope” in the office to check vocal cord function. This procedure involves placing a flexible camera through the nose to visualize the vocal cords and to make sure that they are they are working properly. The procedure is repeated after surgery to evaluate vocal cord function.
To reduce the risk of injury to the nerve during surgery, a special endotracheal tube (breathing tube) can be used. This breathing tube has an electrode that detects and monitors the nerves during surgery.
If a vocal cord is injured during surgery, it is often temporary. However, it may take up to a year and a half to recover. If a patient has a change in voice or difficulty breathing or swallowing, the vocal cords can be injected with a temporary material to improve those functions. A re-innervation procedure may be needed if the nerve does not recover. This procedure connects the non-working recurrent laryngeal nerve with a working nerve to improve the function of the affected vocal cord.
These nerve complications due to thyroidectomy are rare and occur at a rate from 1.4% - 14%. The more experienced the surgeon, the lower the risk of complications.
After surgery, patients will have tests to plan follow-up care. Based on the extent of disease, patients may be monitored or may receive other treatments including radioactive iodine (131I) therapy or additional surgery.
Patients identified as “low risk” may be followed after surgery with periodic screening and TSH suppression with levothyroxine medication. Blocking thyroid stimulating hormone (TSH) keeps this hormone from driving the growth of tumor cells. Monitoring includes testing thyroglobulin and thyroglobulin antibody levels as well as ultrasound imaging to watch for recurrence.
Some “intermediate risk” and all “high risk” patients are assessed with a diagnostic whole body scan and TSH-stimulated thyroglobulin. Whole body scans are used to look for spread of thyroid cancer to other parts of the body. In this test, a special camera detects a radioactive tracer, usually radioiodine (RAI) I-123. Because thyroid cells use iodine to make hormones, this iodine isotope is absorbed specifically by thyroid cells. The picture created in the scan highlights thyroid cancer cells throughout the body. The 123I radiation in this test is very low and is just used for imaging.
Based on the scan results and thyroglobulin levels, radioactive iodine may be used as a treatment. Some patients may have additional surgery if it is possible to remove the disease.
Patients with intermediate and high risk differentiated thyroid cancer may receive treatment with 131I radioactive iodine (RAI). Radioactive iodine therapy is used to destroy thyroid cells. In this therapy, thyroid cells (including thyroid cancer cells) are stimulated to absorb iodine that delivers radiation specifically to the thyroid cells. The radiation kills the cells, even those that have spread to other parts of the body.
However, unlike low-dose 123I used in diagnostic imaging, treatment doses of I-131 have possible acute and late side effects. Some studies suggest that 131I RAI therapy may slightly increase the risk of second cancers, but this is not very well studied in patients treated during childhood or adolescence. The medical team and family must consider the risks of the thyroid cancer, the risks and benefits of treatment, and individual patient needs. Factors such as extent of disease, nature of and response to prior treatment, and other medical conditions may influence treatment plans.
Patients treated for thyroid cancer need lifelong monitoring and follow-up care by an interdisciplinary medical team. Specific recommendations for frequency and types of tests differ according to patient needs and thyroid cancer type and stage.
In differentiated thyroid cancer, thyroglobulin levels can serve as tumor markers to assist in monitoring. Additional considerations include support for adherence to medications including thyroid hormone replacement therapy and TSH suppression.
Key aspects of long-term care:
Recurrence of thyroid cancer can occur many years after treatment. Ongoing monitoring can help with early detection of late recurrences.
Patients can benefit from psychosocial support during treatment and survivorship. Care team members representing Psychology, Child Life, Social Work, and other disciplines can assist with coping and adherence to treatments that may affect quality of life. Possible issues include adjustment to daily medication use, body image concerns due to surgical scars, and other adjustment needs.
Patients may also need physical therapy after surgery to assist with neck mobility and range of motion.
Adjusting to a thyroid cancer diagnosis can be challenging for families. Although the prognosis is generally very good, the disease requires lifelong management through medication and monitoring. Support needs may increase during life transitions such as adolescence and young adulthood as patients gain independence. Adjustment challenges may also be greater for patients who experience thyroid cancer a second cancer.
Patients receiving radioactive iodine therapy should be followed for potential long-term and late effects of treatment. Special considerations include:
For general health and disease prevention, all cancer survivors should adopt healthy lifestyle and eating habits, as well as continue to have regular physical checkups and screenings by a primary physician. Survivors should discuss their medical histories with their health care providers including all cancer therapies.
Reviewed: June 2018