What Is Thyroid Cancer?

The simple versionExplain▾

Thyroid cancer is a disease in which cancer cells form in the tissues of the thyroid gland. The thyroid is a gland at the base of the throat near the trachea (windpipe). It is shaped like a butterfly, with a right lobe and a left lobe. A thin piece of tissue called the isthmus connects the two lobes.

A healthy thyroid is a little larger than a quarter and usually cannot be felt through the skin. Thyroid cancer that is found at an early stage can often be treated successfully.

In short: thyroid cancer starts in the thyroid gland at the base of the throat.

What the thyroid doesExplain▾

The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones. These thyroid hormones do the following:

• Control heart rate, body temperature, and how quickly food is changed into energy (metabolism).
• Control the amount of calcium in the blood.

Thyroid nodulesExplain▾

Sometimes a doctor finds a lump (nodule) in the thyroid during a routine exam. A thyroid nodule is an abnormal growth of thyroid cells that may be solid or fluid-filled.

Thyroid nodules are common but usually are not cancer. They often don't cause symptoms or need treatment. Only a small number of thyroid nodules are diagnosed as cancer. When a nodule is found, an ultrasound of the thyroid and a fine-needle biopsy are often done to check for signs of cancer.

In short: thyroid nodules are common, and most are not cancer.

Types of thyroid cancerExplain▾

There are different types of thyroid cancer, and they differ in how aggressive they are. Thyroid cancer can be described as:

• Differentiated thyroid cancer, which includes well-differentiated tumors, poorly differentiated tumors, and undifferentiated tumors; or
• Medullary thyroid cancer.

Well-differentiated tumors (papillary thyroid cancer and follicular thyroid cancer) can be treated and can usually be cured.

Poorly differentiated and undifferentiated tumors (anaplastic thyroid cancer) are less common. These tumors grow and spread quickly.

Medullary thyroid cancer develops in the C cells of the thyroid. These cells make a hormone called calcitonin, which helps keep a healthy level of calcium in the blood.

Risk factors and finding itExplain▾

Age, sex, and being exposed to radiation can affect the risk of thyroid cancer. Risk factors include being between 25 and 65 years old, being female, being exposed to radiation to the head and neck as an infant or child, having a history of goiter (enlarged thyroid), and having a family history of thyroid disease or thyroid cancer.

Medullary thyroid cancer is sometimes caused by a change in a gene that is passed from parent to child. A genetic test can check for the changed gene.

Thyroid cancer may not cause early signs or symptoms. When they do appear, signs may include a swelling or lump in the neck. Other conditions can cause the same signs, so check with your doctor. Everyone's situation is different, and your care team is the best source of information about your own health.