What types of thyroid cancer are there?
There are four major types of thyroid cancer: papillary thyroid cancer, follicular thyroid cancer, medullary thyroid cancer, and anaplastic thyroid cancer. Doctors can tell the type of cancer by the way the cells look under a microscope and by the way the
Papillary cancer is the most common type, accounting for 60 to 70% of all thyroid cancers. About 2 to 3 times as many women as men have papillary cancer. Papillary cancer is more common in young people but grows and spreads more quickly in older people. People who have received radiation treatment to the neck, usually for a noncancerous condition in infancy or childhood or for some other cancer in adulthood, are at greater risk of developing papillary cancer.
Papillary cancer grows within the thyroid gland but sometimes spreads (metastasizes) to nearby lymph nodes. If left untreated, papillary cancer may spread to more distant sites.
Papillary cancer is almost always curable. Nodules smaller than ¾ inch are removed along with the thyroid tissue immediately surrounding them, although some experts recommend removing the entire thyroid gland. For larger nodules, most or all of the thyroid gland is usually removed. Radioactive iodine is often given to destroy any remaining thyroid tissue or cancer. Thyroid hormone is also given in large doses to suppress the growth of any remaining thyroid tissue.
Follicular cancer accounts for about 15% of all thyroid cancers and is more common among older people. Follicular cancer is also more common in women than in men.
Much more aggressive than papillary cancer, follicular cancer tends to spread (metastasize) through the bloodstream, spreading cancerous cells to various parts of the body. Treatment for follicular cancer requires surgically removing as much of the thyroid gland as possible and destroying any remaining thyroid tissue, including the metastases, if present, with radioactive iodine. It is often curable, but less so than papillary cancer.
Anaplastic cancer accounts for less than 5% of thyroid cancers and is most common among older women. This cancer grows very quickly and usually causes a large growth in the neck. It also tends to spread throughout the body.
About 80% of people with anaplastic cancer die within 1 year, even with treatment. However, treatment with chemotherapy and radiation therapy before and after surgery has resulted in some cures. Radioactive iodine is not helpful in the treatment of this type of cancer.
Medullary cancer begins in the thyroid gland but in a different type of cell than that which produces thyroid hormone. The origin of this cancer is the C-cell, which is normally dispersed throughout the thyroid and secretes the hormone calcitonin. The cancer produces excessive amounts of calcitonin. Because medullary thyroid cancer can also produce other hormones, it can cause unusual symptoms.
This cancer tends to spread (metastasize) through the lymphatic vessels to the lymph nodes and through the blood to the liver, lungs, and bones. Medullary cancer can develop along with other types of endocrine cancers in what is called multiple endocrine neoplasia syndrome (see Multiple Endocrine Neoplasia Syndromes).
Treatment requires surgically removing the thyroid gland. Additional surgery may be needed to determine whether the cancer has spread to the lymph nodes. More than two thirds of people whose medullary thyroid cancer is part of multiple endocrine neoplasia syndrome are cured. When medullary thyroid cancer occurs alone, the chances of survival are not as good.