Cancer of the thyroid is the most common endocrine malignancy, although it is an uncommon cancer, comprising only about 1 percent of invasive cancers.

Although invasive thyroid cancer is uncommon, doctors often have to diagnose and treat thyroid nodules, since about 4 percent of adults develop them.

Thyroid cancer commonly appears as a "cold" nodule, meaning that it does not take up radioactive iodine. About 20 percent of cold nodules are cancer.

About 90 percent of thyroid cancers develop from...