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: - Papillary carcinoma is the most common and usually affects women of child-bearing age. It metastasizes (spreads from the original site) slowly and is the least malignant type of thyroid cancer.
- Follicular carcinoma accounts for about 30% of all cases and has a greater rate of recurrence and metastasis.
- Medullary carcinoma is a cancer of non-thyroid cells in the thyroid gland and tends to occur in families. It requires different treatment from other types of thyroid cancer.
- Anaplastic carcinoma (also called giant and spindle cell cancer) is the most malignant form of thyroid cancer. It is rare, but does not respond to radioiodine therapy. Anaplastic carcinoma metastasizes quickly and invades nearby structures such as the trachea, causing compression and breathing difficulties.
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