From EndocrineWeb: How prevalent is thyroid cancer in the U.S.?. Certainly a diagnosis that is increasing. Increasing so much in fact that we may be changing what our our definition of thyroid cancer is in the next 20 years. Currently we call a lot of lesions “cancer” that are only noticed under the microscope in patients who have their thyroid removed for other reasons, and don’t seem to cause harm if left untreated. More people die with thyroid cancer than die of thyroid cancer.