Home  >  Health Resources  >  Health Encyclopedia

Thyroid Cancer: Introduction

Thyroid Cancer: Introduction

What is cancer?

Cancer is when cells in the body change and grow out of control. To help you understand what happens when you have cancer, let's look at how your body works normally. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them, and die when your body does not need them any longer.

Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby areas. They can even spread to other parts of the body (metastasis).

What is thyroid cancer?

Thyroid cancer starts in the gland called the thyroid.

There are 4 main types of thyroid cancer (carcinoma):

  • Papillary carcinoma. This is the most common type. It affects women more than men.

  • Follicular carcinoma. This more aggressive form accounts for about 10% of all cases of thyroid cancer. 

  • Medullary thyroid carcinoma. This rare type produces a lot of calcitonin and tends to spread. 

  • Anaplastic carcinoma. This very rare type grows quickly and tends to spread. It can be hard to treat.

Illustration of the thyroid glad and its location
Thyroid Gland - Click to Enlarge

Most thyroid changes are not cancer

Changes in the thyroid gland are often easy to see. Lumps or bumps, called nodules, are common. They may not need to be treated. Not all of them are cancer. Growths that are not cancer don’t spread from the thyroid to other parts of your body. But cancer from the thyroid gland can either stay there or spread.

Thyroid adenomas are small nodules that start in the cell layer that lines the inner surface of the thyroid gland. They are not cancer. The adenoma itself may produce or secrete thyroid hormone. If it produces enough thyroid hormone, it may cause hyperthyroidism. This is a condition where your body has too much thyroid hormone. This may need to be treated.

Some signs that a nodule may be cancer and not an adenoma include:

  • There is one nodule rather than many nodules

  • A thyroid scan shows the nodule is not working

  • The nodule is solid instead of filled with fluid, like a cyst

  • The nodule is hard

  • The nodule grows fast

The thyroid gland is in the front of your neck. It is under your Adam’s apple and above your collar bone. You often can’t see or feel your thyroid. It faces the front, but it’s underneath your skin. It’s shaped like a butterfly with 2 lobes, a right and left lobe. The lobes are joined by a bridge of tissue, called the isthmus. The thyroid is made up of 2 main types of cells. The follicular cells make and store thyroid hormones which control your metabolism. The C cells, or parafollicular cells, make the hormone calcitonin. This helps control calcium levels in your body. 

How thyroid cancer spreads

When thyroid cancer spreads outside the thyroid gland, it typically goes to nearby lymph nodes. It can also spread to nearby blood vessels and other tissues in the neck. Over time, it can spread to distant parts of the body, such as the lungs and bones.

Talk with your healthcare provider

If you have questions about thyroid cancer, talk with your healthcare provider. Your healthcare provider can help you understand more about this cancer. 


Today's Interactive Tools