There are a number of types of thyroid cancer with a wide range of varying characteristics. The following are brief descriptions of several forms of thyroid cancer:
- Papillary Thyroid Cancer is the most common, representing eight out of 10 cases. This cancer develops in the follicular cells, grows slowly, and often appears in only one lobe of the thyroid, though it is known to spread to the lymph nodes. The disease can develop in anyone but affects women three times more often than men (usually between the ages of 30 and 50).
- Follicular Thyroid Cancer also develops in the follicular cells and grows slowly, but it is a less common cancer (only one out of 10 cases in the United States). Advanced follicular cancer may spread to other organs such as lung and bone. This cancer is more common in areas of the world where people do not get enough iodine in their diet.
- Medullary Thyroid Cancer (MTC) is rare, accounting for approximately five percent of all thyroid cancers. This disease begins in the C cells and can produce abnormally high levels of calcitonin. There are two types of MTC: sporadic and familial. Eight out of 10 cases are of the sporadic type. Sporadic MTC is not inherited (not passed from generation to generation through a family), is usually found in only one lobe of the thyroid, and typically affects adults ages 40 to 60. Familial MTC is caused by inheriting an abnormal gene (the RET gene), develops at any age (but most typically before age 40), and can spread to other parts of the body. It accounts for about one out of five MTCs.
- Anaplastic Thyroid Cancer is a rare and very aggressive form of thyroid cancer, representing only two percent of all thyroid cancer cases. Believed to form from an existing papillary or follicular cancer, anaplastic cancer spreads rapidly to the lymph nodes in the neck, the trachea, and other organs, particularly the lung and bone.
- Thyroid Lymphoma represents less than one percent of thyroid cancers. It is a very uncommon form of lymphoma that begins in the immune system cells (lymphocytes) of the thyroid and typically affects older women.
- Metastatic Thyroid Cancer is thyroid cancer that has spread to other parts of the body. Most often thyroid cancer spreads to the lymph nodes, lungs, and bones.