About the Thyroid
The thyroid is a small gland located in the front of the neck beneath the voice box (larynx). The thyroid has two lobes connected by a thin piece of tissue called the isthmus. The thyroid contains follicular cells that use iodine from your diet to make thyroid hormone. Thyroid hormone regulates your body’s metabolism by affecting heart rate, blood pressure, body temperature and weight. The C cells of the thyroid make calcitonin that plays a minor role in regulating calcium levels in the body.
Four tiny parathyroid glands are located behind the thyroid on its surface. The parathyroid glands are very important in maintaining a normal calcium level in the body.
Some cells in the thyroid may grow and divide faster than others to form a nodule. Most thyroid nodules are not malignant but about 5-10% are malignant
Thyroid cancer begins when cells in the thyroid gland grow and divide uncontrollably to form a tumor that can invade blood and lymph vessels.
The Thyroid Cancer Team includes, among others you might see:
Thomas Galloway, MD
About Thyroid Cancer
The diagnosis of thyroid cancer is increasing faster than any other malignancy, partly due to increased detection of small tumors with ultrasound, CT scans and PET scans. It is estimated that there will be about 48,020 new cases of thyroid cancer diagnosed in 2011 in the United States. Thyroid cancer is one of the most curable cancers with excellent survival rates in the majority of cases. There are nearly 500,000 cancer survivors in the United States.
Differentiated Thyroid Cancer
Papillary Thyroid Cancer
About 80% of all thyroid cancer in the United States is caused by papillary thyroid cancer. It is usually a slow growing cancer that may spread to the lymph nodes in the neck. If diagnosed early, most people with this type of cancer can be cured.
Follicular Thyroid Cancer
This type makes up about 15% of all thyroid cancers. Follicular thyroid cancer is also slow growing and can often be cured. Follicular thyroid cancer can spread to the lungs, bone, or, rarely, to the lymph nodes in the neck.
Hurthle Cell Thyroid Cancer
Hurthle cell cancer is a rare type of follicular thyroid cancer. Complete surgical removal of small Hurthle cell cancers confined to the thyroid can be curative. Hurthle cell cancer not cured by surgery can be more difficult to treat than papillary or follicular thyroid cancer since the Hurthle cells often do not absorb radioactive iodine.
Other Thyroid Cancers
Medullary Thyroid Cancer
This is a less common type of cancer that affects the C cells of the thyroid that make calcitonin. It may be caused by a genetic mutation that runs in some families or occurs spontaneously. High levels of calcitonin and carcinoembryonic antigen (CEA) are usually seen in medullary thyroid cancer. Medullary thyroid cancer tends to grow slowly but some of the familial forms can be more aggressive.
Anaplastic Thyroid Cancer
Only about 2% of all thyroid cancers are anaplastic. It begins in the follicular cells and tends to grow and spread rapidly. Anaplastic thyroid cancer is very difficult to control.
The most important risk factor for the development of thyroid cancer is exposure to radiation during childhood or adolescence. From the 1920’s through the 1950’s, x-rays were used to treat children with enlarged tonsils, acne, and other problems of the head and neck. As adults, these patients have an increased risk of developing thyroid cancer. Children and adults who were treated with radiation for cancers of the head or neck also have an increased risk of thyroid cancer. People who were exposed to ionizing radiation as children or adolescents from the Chernobyl or Fukashima nuclear disasters have an increased risk of thyroid cancer.
Family history of thyroid cancer
Medullary thyroid cancer sometimes runs in families due to a mutation of the RET gene that can be passed from parent to child. Genetic screening and testing are available at Fox Chase Cancer Center for patients and family members suspected of having the mutated gene. A history of any type of thyroid cancer in a first degree relative (parents, offspring, and siblings) is also a risk factor.
Family History of Multiple Colonic Polyps or Other Tumor Syndromes
People with a family history of multiple growths in the colon, such as in a condition called familial adenomatous polyposis (FAP) have an increased risk of thyroid cancer. Other tumor syndromes such as Carney Complex, Cowden’s syndrome, Werner Syndrome increase the risk of thyroid cancer.
In the US, women are almost 3 times more likely than men to develop thyroid cancer. However, thyroid cancer tends to be more aggressive in men.
Iodine is found in shellfish and iodized salt. The diet in the United States is generally iodine sufficient due to the widespread use of iodized salt, but many areas of the world remain iodine deficient. The role of iodine in the development of thyroid cancer is unclear. In iodine deficient areas of the world, there is a higher prevalence of follicular thyroid cancer. Papillary thyroid cancer has been shown to increase in frequency in some areas after iodine is supplemented in the diet. More studies are needed to know whether iodine is a risk factor.
Many patients with early thyroid cancer have no noticeable symptoms. As the cancer grows, a swelling or lump on the front of the neck is often the first symptom. Thyroid nodules are common and are usually painless. The vast majority of them are benign.
Other less common symptoms of thyroid cancer may include:
- trouble swallowing
- persistently swollen glands in the neck
- difficulty breathing
- pain in the throat or neck that does not go away
- a cough that does not go away and is not due to a cold
Symptoms of thyroid cancer may be similar to those of other medical conditions. If you are concerned about a symptom on this list, you should see your doctor.
If you have symptoms that suggest thyroid cancer, your doctor will help you find out whether they are from thyroid cancer or some other cause. Your doctor will ask about your personal and family medical history. You may have one or more of the following tests:
- Physical exam: Your doctor may examine your neck for lumps or large lymph nodes.
- Blood Tests: Tests of the thyroid function such as the thyroid-stimulating hormone (TSH) or calcitonin may be checked.
- Ultrasound: The ultrasound uses sound waves to create a picture of the thyroid. It is the best way to see the thyroid and the neck lymph nodes in great detail. Sometimes the appearance on the ultrasound can tell us whether a nodule is more likely to be cancerous.
- Thyroid Scan: Your doctor may order a scan of your thyroid to see if any of the nodules absorb iodine. You swallow a small amount of radioactive iodine that travels to your thyroid. Nodules that absorb more iodine than the rest of the thyroid are called “hot” nodules and usually do not require biopsy since they are rarely cancer.
- Fine Needle Aspiration (FNA) Biopsy: A biopsy is the only sure way to diagnose thyroid cancer. The blood tests and ultrasound pictures are used to determine which nodule(s) require biopsy. Using the ultrasound device to locate the suspicious nodule(s), a very fine needle can remove a sample of the tissue. A pathologist checks the samples for cancer cells with a microscope.
- Surgery: Sometimes the cells obtained from the FNA biopsy do not provided enough information to tell if the nodule is benign or cancerous. In those cases, the lobe containing the nodule must be removed surgically to determine the diagnosis.
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