Definition of Thyroid cancer:

Thyroid cancer is a cancerous growth of the thyroid gland.

Causes, incidence, and risk factors:

Thyroid cancer can occur in all age groups.

People who have had radiation therapy to the neck are at higher risk. This therapy was commonly used in the 1950s to treat enlarged thymus glands, adenoids and tonsils, and skin disorders. People who received radiation therapy as children have a higher incidence of thyroid cancer.

Other risk factors are a family history of thyroid cancer and chronic goiter. The disease affects 1 in 1,000 people.

There are several types of thyroid cancer:

• Anaplastic carcinoma (also called giant and spindle cell cancer) is the most dangerous form of thyroid cancer. It is rare, but does not respond to radioiodine therapy. Anaplastic carcinoma spreads quickly and invades nearby structures such as the trachea, causing breathing difficulties.
• Follicular carcinoma accounts for about 30% of all cases and is more likely to come back and spread.
• Medullary carcinoma is a cancer of non-thyroid cells in the thyroid gland and tends to occur in families. It requires different treatment than other types of thyroid cancer.
• Papillary carcinoma is the most common type, and usually affects women of childbearing age. It spreads slowly and is the least dangerous type of thyroid cancer.