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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 the thyroid gland?



Thyroid Gland - Click to Enlarge

The thyroid gland is part of the endocrine system. It helps control hormones in your body. It's in the front of your neck, over your windpipe (trachea). It's 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. Thyroid hormones control your metabolism. The C cells, or parafollicular cells, make the hormone calcitonin. This helps control calcium levels in your body.

What is thyroid cancer?

Thyroid cancer starts in the cells of the thyroid gland.

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 is a more aggressive form of thyroid cancer. It accounts for about 10% of all cases. 

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

  • Anaplastic carcinoma. This is a very rare type of thyroid cancer. It grows quickly and tends to spread. It can be hard to treat.

Illustration of the thyroid glad and its location

Most thyroid changes are not cancer

Changes in the thyroid gland are often easy to see and feel. 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. 

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:

  • 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 and not tender

  • The nodule grows fast

  • Lymph nodes around the thyroid gland are enlarged 

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.