Growth of abnormal cells that form nodules in the thyroid gland is the most common endocrine problem in the United States. Each year more than 25,000 women and 8,000 men are diagnosed with thyroid cancer in the United States. There are several histological types of thyroid cancer, the more common to less common being papillary thyroid cancer (PTC), follicular thyroid cancer (FTC), medullary thyroid cancer (MTC) and anaplastic thyroid cancer (ATC). PTC, FTC and ATC originate from follicular cells of the thyroid, whereas MTC originates from the parafollicular or calcitonin-producing (C) cells in the thyroid gland. PTC and FTC (including a subtype of Hurthle cell carcinoma, HCC) are composed of cancer cells that are considered well differentiated and account for 80 and 15 percent of all thyroid cancer in the U.S., respectively. In contrast, the cells of MTC and ATC are considered less differentiated, or dedifferentiated and account for about 3-5 percent each of all thyroid cancer. Individuals diagnosed with PTC, FTC and MTC generally have a good prognosis, whereas ATC is the most aggressive and the least likely form of thyroid cancer to respond to treatment, with a median survival of 4-12 months from the time of diagnosis.
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