Thyroid cancer is the most common endocrine malignancy; thyroid cancer is a malignant tumor or mass that grows in the thyroid gland; thyroid cancer is one of the few cancers whose incidence is increasing every year. Women are more likely to develop thyroid cancer than men, with more than seven out of ten thyroid cancer patients being female. The cause of most thyroid cancers is unknown. Those who have been exposed to high levels of radiation as children or who have received radiation treatment for head or neck conditions at a young age are more likely to develop thyroid cancer. Thyroid cancer may develop 20 years after radiation exposure. However, most people who have been exposed to radiation do not develop thyroid cancer, and most people with thyroid cancer have not been exposed to radiation. The prognosis of a patient with thyroid cancer depends on several factors: the type of thyroid cancer, the size of the tumor, whether the thyroid cancer has spread (metastasized) to other parts of the body (especially far from the thyroid gland), and the age of the patient at the time of diagnosis. Thyroid cancer is usually very well treated if detected early.