Definition of thyroid cancer: Cancer that forms in the thyroid gland (an organ at the base of the throat that makes hormones that help control heart rate, blood pressure, body temperature, and weight). Four main types of thyroid cancer are papillary, follicular, medullary, and anaplastic thyroid cancer. The four types are based on how the cancer cells look under a microscope.
Estimated new cases and deaths from thyroid cancer in the United States in 2011:
New cases: 48,020
Source: National Cancer Institute