Thyroid cancer occurs in the cells of the thyroid — a butterfly-shaped gland located at the base of your neck, just below your Adam’s apple. Your thyroid produces hormones that regulate your heart rate, blood pressure, body temperature, and weight.

Thyroid cancer might not cause any symptoms at first. But as it grows, it can cause pain and swell in your neck.

Several types of thyroid cancer exist. Some grow very slowly and others can be very aggressive. Most cases of thyroid cancer can be cured with treatment.

Thyroid cancer rates seem to be increasing. Some doctors think this is because new technology is allowing them to find small thyroid cancers that may not have been found in the past.

Types of thyroid cancer include:

• Papillary thyroid cancer.The most common form of thyroid cancer, papillary thyroid cancer arises from follicular cells, which produce and store thyroid hormones. Papillary thyroid cancer can occur at any age, but most often it affects people ages 30 to 50. Doctors sometimes refer to papillary thyroid cancer and follicular thyroid cancer together as differentiated thyroid cancer.
• Follicular thyroid cancer.Follicular thyroid cancer also arises from the follicular cells of the thyroid. It usually affects people older than age 50. Hurthle cell cancer is a rare and potentially more aggressive type of follicular thyroid cancer.
• Anaplastic thyroid cancer.Anaplastic thyroid cancer is a rare type of thyroid cancer that begins in the follicular cells. It grows rapidly and is very difficult to treat. Anaplastic thyroid cancer typically occurs in adults age 60 and older.
• Medullary thyroid cancer.Medullary thyroid cancer begins in thyroid cells called C cells, which produce the hormone calcitonin. Elevated levels of calcitonin in the blood can indicate medullary thyroid cancer at a very early stage. Certain genetic syndromes increase the risk of medullary thyroid cancer, although this genetic link is uncommon.
• Other rare types.Other very rare types of cancer that start in the thyroid include thyroid lymphoma, which begins in the immune system cells of the thyroid, and thyroid sarcoma, which begins in the connective tissue cells of the thyroid.