Introduction

Many types of tumors can develop in the thyroid gland. The thyroid gland is located in the front of the neck. It makes a hormone (called the thyroid hormone) that helps control heart rate, blood pressure, body temperature, and weight. About 44,670 people in the United States will be diagnosed with thyroid cancer in 2010, according to the American Cancer Society. Thyroid cancer is more common in women than in men, and most patients with thyroid cancer are older than 40.

Most thyroid tumors are benign (noncancerous). Those that are cancerous can spread into nearby tissues and to other parts of the body. Most thyroid cancers develop from the thyroid follicle cells, which make the thyroid hormone, and typically grow very slowly. They usually occur in only one lobe of the thyroid gland, but sometimes they involve both lobes.

At first, people with thyroid cancer might not notice any symptoms. Some people with thyroid cancer have a lump in the front of the neck, just below the Adam's apple. Sometimes this lump grows rapidly. Other possible symptoms are hoarseness, difficulty swallowing, trouble breathing, swollen lymph nodes (especially in the neck), and pain in the throat or neck.

In most cases, it is impossible to know what causes someone to develop thyroid cancer. However, people who have had head or neck radiation treatment for acne or other childhood diseases as children have a higher risk of thyroid cancer, although the cancer might not develop for at least 10 years after the radiation. People who have been exposed to radiation from a nuclear fallout also have an increased risk of thyroid cancer. In a few cases, thyroid cancer is caused by a change in a gene called RET, which can be passed from parent to child.