Education: Thyroid & Endocrine Cancers
Endocrine cancer is cancer that occurs in the endocrine tissue (the tissue in the body that secretes hormones). The endocrine system is a collection of hormone-producing glands that control basic body functions such as metabolism, growth and sexual development. The endocrine system consists of the pituitary gland, hypothalamus, pancreas, adrenal cortex, thyroid gland, parathyroid glands, and gonads.
Thyroid cancer is the most common cancer of the endocrine system. According to the American Cancer Society, more than 40,000 new cases of thyroid cancer are diagnosed annually in the U.S., with approximately 30,000 cases in women, and 10,000 cases in men.
Thyroid cancer starts in the thyroid glands. The thyroid gland is located in the front of the neck, below the voice box. It contains mainly two types of cells: thyroid follicular cells and C cells (also called parafollicular cells). The C cells secrete calcitonin, a hormone that regulates how the body uses calcium while the follicular cells use iodine from the blood to make thyroid hormone, which helps regulate a person’s metabolism.
What Are the Different Types of Thyroid Cancer?
The four main types of thyroid cancer are papillary, follicular, medullary, and anaplastic thyroid cancer. The four types are based on how the cancer cells look under a microscope.
About 8 of 10 thyroid cancers are papillary cancers. Usually they develop in only one lobe of the thyroid gland, but sometimes they occur in both lobes. Papillary carcinomas often spread to the lymph nodes in the neck. But most of the time, this can be successfully treated and is rarely fatal. Follicular carcinoma is the next most common type of thyroid cancer. These cancers usually remain in the thyroid gland. Unlike papillary carcinoma, follicular carcinomas usually don’t spread to lymph nodes, but some can spread to other parts of the body, such as the lungs or bones.
Medullary thyroid cancer develops from the C cells of the thyroid gland. Sometimes this cancer can spread to lymph nodes, the lungs, or liver even before a thyroid nodule is discovered. These cancers usually release calcitonin and carcinoembryonic antigen (CEA) into the blood, causing high levels of these when checked by blood tests. Anaplastic cancer (also called undifferentiated carcinoma) is a rare form of thyroid cancer. It is thought to sometimes develop from an existing papillary or follicular cancer. This cancer is called undifferentiated because the cancer cells do not look very much like normal thyroid tissue cells under the microscope. This is an aggressive cancer that rapidly invades the neck, often spreads to other parts of the body, and is very hard to treat.
Thyroid cancer is different from many other adult cancers in that it is commonly diagnosed in younger people. Nearly 2 of 3 cases are found in people between the ages of 20 and 55. Thyroid cancer occurs about three times more often in women than in men. Other factors include:
- A low iodine diet
- Exposure to radiation in childhood
- Heredity conditions
- Other thyroid cancers