What is Thyroid Cancer?
Thyroid cancer in children is a rare disease in which cancer (malignant) cells are found in the tissues of a child’s thyroid. The thyroid is a gland in the neck. It has two kinds of cells that make hormones. Follicular cells make thyroid hormone, which affects heart rate, body temperature and energy level. C cells make calcitonin, a hormone that helps control the level of calcium in the blood. Growths or tumors on the thyroid are usually called nodules, which can be benign or malignant:
- Benign nodules – These are not cancer and usually not a threat to life. Most thyroid nodules (more than 90 percent) are benign.
- Malignant nodules – These are cancer, and are generally more serious and may sometimes be life threatening.
In the United States, thyroid cancer represents 1% to 1.5% of all pediatric cancers, and 5% to 5.7% of malignancies in the head and neck. Thyroid nodules occur only in 4% to 7% of the general adult population, and in only 1% to 2% of the pediatric population. The incidence of malignancy is much higher in pediatric nodules. Five percent of nodules in adults are malignant; in the pediatric population, the percentage of malignant nodules is 33%.
The following are the major types of thyroid cancer:
- Papillary and follicular thyroid cancers -- These account for 80% to 90% of all thyroid cancers. Both types begin in the follicular cells of the thyroid. Most papillary and follicular thyroid cancers tend to grow slowly. If they are detected early, most can be treated successfully.
- Medullary thyroid cancer – These account for 5% to 10% of thyroid cancer cases. It arises in C cells, not follicular cells. Medullary thyroid cancer is easier to control if it is found and treated before it spreads to other parts of the body.
- Anaplastic thyroid cancer – This is the least common type of thyroid cancer and arises in the follicular cells. This type of cancer is usually very hard to control because the cancer cells tend to grow and spread very quickly.
Pediatric thyroid cancer is usually a papillary subtype of the papillary-follicular subtype, but all types of thyroid cancer have been observed. Pediatric patients seem to have higher local and distance recurrent rates than adults, but respond rapidly to therapy. The prognosis for children is excellent, with mortality rates of less than 10%. Pediatric thyroid cancer occurs more frequently in adolescents, but has also been observed in the neonatal period. It is also two to three times more common in females.
Research has shown that people with certain risk factors are more likely than others to develop thyroid cancer.
These risk factors include:
- Radiation – People exposed to high levels of radiation are much more likely than others to develop papillary or follicular thyroid cancer.
- Family history – Medullary thyroid cancer can be caused by a change, or alteration, in a gene called RET. The RET gene can be passed from parent to child. Nearly everyone with the altered RET gene will develop medullary thyroid cancer. A blood test can detect an altered RET gene. When medullary thyroid cancer runs in a family, the doctor may call this “familial medullary thyroid cancer.”
- Race – In the United States, white people are more likely than African Americans to be diagnosed with thyroid cancer.
- Not enough iodine in the diet – The thyroid needs iodine to make thyroid hormone. In the United States, iodine is added to salt to protect people from thyroid problems. Thyroid cancer seems to be less common in the United States than in countries where iodine is not part of the diet.
What are the symptoms of Thyroid Cancer?
Early thyroid cancer often does not cause symptoms. But as the cancer grows, symptoms may include:
- A lump, or nodule, in the front of the neck near the Adam’s apple
- Hoarseness or difficulty speaking in a normal voice
- Swollen lymph nodes, especially in the neck
- Difficulty swallowing or breathing
- Pain in the throat
How is Thyroid Cancer diagnosed?
The accurate diagnosis of thyroid cancer is crucial in tailoring an optimal treatment plan. The doctor will first ask about symptoms and medical history. The doctor will then perform a thorough physical examination.
A diagnosis may be confirmed by a series of tests, which can include:
- Blood Tests – The doctor may test for abnormal levels (too low or too high) of thyroid-stimulating hormone (TSH) in the blood. TSH controls how fast thyroid follicular cells grow. If medullary thyroid cancer is suspected, the doctor may check for abnormally high levels of calcium in the blood. The doctor may order blood tests to detect an altered RET gene or to look for a high level of calcitonin.
- Radionuclide scanning – This scan uses a very small amount of radioactive material to make thyroid nodules show up on a picture.
- Biopsy -- This involves removing a small piece of the thyroid to examine under a microscope. The doctor may remove the tissue through a needle or during surgery.
- Magnetic resonance imaging (MRI)
- Computed tomography (CT)
Treatment for Thyroid Cancer:
There are different treatment options for thyroid cancer:
Is the most common treatment for thyroid cancer. The surgeon may remove all or part of the thyroid. The type of surgery depends on the type and stage of thyroid cancer, the size of the nodule and the patient’s age. Nearly all patients who have part or all of the thyroid removed will take thyroid hormone pills to replace the natural hormone.
Radioactive iodine therapy
Radioactive iodine therapy (also called radioiodine therapy) uses radioactive iodine (I-131) to destroy thyroid cancer cells anywhere in the body. The therapy usually is given by mouth in a small dose that causes no problems for people who are allergic to iodine. Since pediatric patients are few and the prognosis is generally excellent, this treatment approach is usually recommended only for patients with extensive nodal involvement that cannot be removed by surgery, invasion of vital structures or distant metastases.
External radiation therapy
External radiation therapy, also called radiotherapy, uses high-energy rays to kill cancer cells. A large machine directs radiation at the neck or at parts of the body where the cancer has spread. This approach is used mainly to treat people with advanced thyroid cancer that does not respond to radioactive iodine therapy.
Chemotherapy uses drugs to kill cancer cells. For some patients, chemotherapy may be combined with external radiation therapy.