Thyroid cancer develops as a result of the uncontrolled growth of abnormal cells in the thyroid gland, resulting in a tumor. Some of these tumors are benign or non cancerous while some are malignant or cancerous. The malignant tumors spread to the nearby tissues and other parts of the body causing severe complications. Since the thyroid gland is close to the skin, tumors often appear as lumps called thyroid nodules in the neck. Thyroid cancer is more widespread among women than men; however, the reason for this is not clear. About 20,000 cases of thyroid cancer are reported each year in the United States.

The precise causes of thyroid cancer remain vague. Some studies reveal that people who are exposed to large amounts of radiation or those who have undergone radiation treatments for medical purposes, especially on the head and neck, face an increased risk of developing thyroid cancer. The occurrence of thyroid cancer is high in countries where people follow a low iodine diet. People with certain medical conditions or a family history of thyroid disease have a higher risk of developing thyroid cancer. Incidents of thyroid cancer arise mainly in the age group of 25 to 65 years.

Thyroid cancer may be papillary, follicular, medullary, or anaplastic. A fine needle aspiration (FNA) test is an ideal test for thyroid cancer. Papillary is the most usual type, while Follicular is a less common one usually found in older people. Medullary and anaplastic are rare types, the former often hereditary and the latter fast-growing one seen more among older people. The anaplastic type is difficult to treat. Thyroid cancers tend to develop at a slow pace, and it may take some time before any symptoms appear. Most types of thyroid cancer can be treated successfully with early detection and appropriate surgical procedures.