Topic updated: July 2012

Thyroid Cancer

The Thyroid

Your thyroid is a gland at the front of your neck beneath your voice box (larynx). A healthy thyroid is a little larger than a quarter. It usually cannot be felt through the skin.

The thyroid has two parts (lobes). A thin piece of tissue (the isthmus) separates the lobes.

The thyroid makes hormones:

Four or more tiny parathyroid glands are on the back of the thyroid. These glands make parathyroid hormone. This hormone plays a big role in helping the body maintain a healthy level of calcium.

Understanding Cancer

Cancer begins in cells, the building blocks that make up tissues. Tissues make up the thyroid and other organsof the body.

Normal thyroid cells grow and divide to form new cells as the body needs them. When normal cells grow old or get damaged, they die, and new cells take their place.

Sometimes, this process goes wrong. New cells form when the body does not need them, and old or damaged cells do not die as they should. The buildup of extra cells often forms a mass of tissue called a nodule. It may also be called a growth or tumor.

Most thyroid nodules are benign. Benign nodules are not cancer (malignant):

  • Benign nodules
    • Are usually not harmful
    • Don’t invade the tissues around them
    • Don’t spread to other parts of the body
    • Usually don’t need to be removed
  • Malignant nodules (Thyroid Cancer)
    • May sometimes be a threat to life
    • Can invade nearby tissues and organs
    • Can spread to other parts of the body
    • Often can be removed or destroyed, but sometimes thyroid cancer returns

Thyroid cancer cells can spread by breaking away from the thyroid tumor. They can travel through lymph vesselsto nearby lymph nodes. They can also spread through blood vessels to the lungs, liver, or bones. After spreading, cancer cells may attach to other tissues and grow to form new tumors that may damage those tissues.

Types of Thyroid Cancer

There are several types of thyroid cancer:

  • Papillary: In the United States, papillary thyroid cancer is the most common type. About 86 of every 100 people with thyroid cancer have this type. It begins in follicular cells and usually grows slowly. If diagnosed early, most people with papillary thyroid cancer can be cured.
  • Follicular: The second most common type is follicular thyroid cancer. A little more than 9 of every 100 people with thyroid cancer have this type. It begins in follicular cells and usually grows slowly. If diagnosed early, most people with follicular thyroid cancer can be treated successfully.
  • Medullary: Medullary thyroid cancer is not common. About 2 of every 100 people with thyroid cancer have this type. It begins in C cells and can make abnormally high levels of calcitonin. Medullary thyroid cancer tends to grow slowly. It can be easier to control if it’s found and treated before it spreads to other parts of the body.
  • Anaplastic: The least common type is anaplastic thyroid cancer. About 1 of every 100 people with thyroid cancer has this type. Most people with anaplastic thyroid cancer are older than 60. The cancer begins in follicular cells of the thyroid. The cancer cells tend to grow and spread very quickly. Anaplastic thyroid cancer is very hard to control.

Tests and treatment options depend on the type of thyroid cancer.

Read the rest of this excellent article from the National Cancer Institute.

Thyroid image reproduced with permission from Philip Wilson, Medical & Scientific Illustrator in Orpington, Kent, England. All rights reserved. For more information see their website at: www.medart.co.uk

Illustration of thyroid

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