Adapted for the Canadian edition by Richard Tsang, MD
Cancer of the thyroid is the most common endocrine malignancy but is an uncommon cancer, comprising only about 1 percent of invasive cancers. It is estimated that there will be about 1,100 new cases in 1995, 800 in women and 300 in men. People with these malignancies are usually treated successfully.
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.
Most cases occur between 25 and 65 years of age, and the age at diagnosis is one of the most important factors in predicting prognosis. Men under 40 and women under 50 have significantly lower rates of recurrence and better survival rates than older patients.
Types About 90 percent of thyroid cancers develop from the follicular cells . Some develop from the parafollicular cells or C cells (medullary). Patients with well-differentiated tumors generally have a good prognosis. Those with undifferentiated or anaplastic tumors do not.
