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Thyroid cancer is a malignant growth of the cells in the thyroid gland.
The thyroid is an endocrine gland located in the lower neck. It is shaped a bit like a butterfly, with a thin central body (or isthmus) and two “wings” or lobes. Like all endocrine glands, the thyroid produces hormones—chemicals that circulate through the blood to direct functioning in other organs of the body. The thyroid is made up of two types of cells, follicular cells and C cells. The follicular cells produce thyroid hormone, which is involved in regulating body temperature, heart rate, and the body’s use of energy. The C cells produce calcitonin, which is involved in the processing and use of calcium throughout the body.
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A thyroid tumor grows when cells of the thyroid become cancerous. These cancer cells begin to divide and multiply more quickly than normal cells. Cancer cells also lack the ability to organize themselves in a normal way and have the capability to invade other normal tissue. Growths on the thyroid are often called thyroid nodules. They can be benign (not cancerous) or malignant (cancerous). Luckily, the vast majority (more than 90%) of thyroid nodules are benign.
There are 4 main types of thyroid cancer:
Thyroid cancer is the most common type of endocrine gland cancer. About 14,000 cases of thyroid cancer are diagnosed each year, and about 1,100 deaths occur annually due to thyroid cancer. Women are about three times as likely as men to develop thyroid cancer. The average thyroid cancer patient is 45–50 years old when diagnosed.
No one knows exactly what causes thyroid cancer. It is clear, however, that certain situations greatly increase a person’s risk of developing the disease. For example, people who have been exposed to radiation (either after nuclear bomb fallout, or through medical use of radiation to the head, neck, chest, or back) have a higher risk of developing thyroid cancer than those who have not. Medullary thyroid cancer also runs in certain families, along with other endocrine cancers. People who have had other conditions affecting their thyroid (chronic goiter, sometimes due to too little iodine in the diet) are also at somewhat greater risk of developing thyroid cancer in the future.
Thyroid cancer can cause an enlarging lump in the neck, hoarseness, difficulty swallowing, and a harsh sound while breathing (called stridor). If thyroid cancer is left untreated, it can spread outside of the thyroid to the nearby lymph nodes, nerves, and blood vessels. It can also spread to distant sites within the body. This is called metastasis. When thyroid cancer spreads, it tends to metastasize to lungs, liver, and bone.
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Thyroid cancer. American Cancer Society website. Available at http://www.cancer.org/acs/groups/cid/documents/webcontent/003144-pdf.pdf. Accessed September 17, 2014.
Thyroid cancer—for patients. National Cancer Institute website. Available at http://www.cancer.gov/types/thyroid. Accessed September 17, 2014.
Thyroid carcinoma. In: Cecil Textbook of Medicine. 21st ed. Philadelphia, PA: WB Saunders Company; 2000: 1247-1250.
Last reviewed September 2016 by Mohei Abouzied, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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