Thyroid Cancer (cont.)

The 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 can't be felt through the skin.

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

The thyroid makes hormones:

• Thyroid hormone: The thyroid follicular cells make thyroid hormone. This hormone affects heart rate, blood pressure, body temperature, and weight. For example, too much thyroid hormone makes your heart race, and too little makes you feel very tired.
• Calcitonin: The C cells in the thyroid make calcitonin. This hormone plays a small role in keeping a healthy level of calcium in the body.

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.

Cancer begins in cells, the building blocks that make up tissues. Tissues make up the thyroid and other organs of 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 vessels to 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.

See the Staging section for information about thyroid cancer that has spread.

Source: MedicineNet.com
http://www.medicinenet.com/thyroid_cancer/article.htm