What Are the Stages of Thyroid Cancer?

Medically Reviewed by Jennifer Robinson, MD on June 18, 2024
4 min read

If you or someone you love has thyroid cancer, you want to know what treatments are available and what to expect. This depends on several things – starting with what type of thyroid cancer you have and its stage.

It’s easy to get swamped by the numbers, letters, and unfamiliar words, even when you’re not under stress. This article will help you make better sense of what is happening based on the cancer’s stage.

The thyroid is a gland at the base of your throat. It makes hormones that help your body work properly.

There are four main types of thyroid cancer:

  • Papillary (the most common type)
  • Follicular
  • Medullary
  • Anaplastic

If your doctor finds cancer, they’ll begin the process of staging. They’ll run tests to see if it has spread to other parts of your body.

The American Joint Committee on Cancer created the system that’s most often used to describe the stages of thyroid cancer. It’s called the “TNM” system, and it focuses on these three things:

  • T -- What is the size and extent of the main, or primary, tumor?
  • N -- Has the cancer spread to nearby lymph nodes? (These are bean-shaped cells that help your body fight infection).
  • M -- Has the cancer spread, or metastasized, to other areas of the body or organs, namely the lungs, liver, and bones?

After your doctor runs tests to find out what type of thyroid cancer you have, they’ll add a number to each letter listed above. The higher the number, the more advanced is that aspect of the cancer. (For example, T2-T4 means a larger tumor than T1).

Next, your doctor will group this information into stages. These are represented by the Roman numerals I through IV. For the most advanced cases, the letters “A,” “B” and “C” also are used to indicate how far the cancer has spread.

What type of cancer you have, as well as your age, will have some bearing on your stage.

Here’s what each stage of thyroid cancer means, grouped by type:

  • Stage I -- The tumor can be any size. It may have spread to nearby tissues or nearby lymph nodes. But it hasn’t spread to other parts of the body.
  • Stage II -- The tumor is any size. Cancer may have spread to your lymph nodes. It also has spread to other parts of your body, like your lungs or bones.
  • Stage I -- You only have cancer in your thyroid. The tumor is 2 centimeters (about the size of a nickel) or smaller and hasn't spread.
  • Stage II -- You only have cancer in your thyroid. The tumor is any size but is nowhere else in your body.
  • Stage III --The tumor is any size and has spread to tissues near your thyroid, or it’s smaller and has reached your nearby lymph nodes.

If you are at stage IV, it means the cancer has spread. Your doctor assigns the letters “A,” “B” and “C” to show how far.

  • Stage IVA -- The cancer has spread beyond your thyroid. It now is under your skin, or it affects your larynx, esophagus or trachea. A smaller tumor in more distant lymph nodes is also considered stage IVA.
  • Stage IVB -- The tumor has grown toward your spine or into nearby large blood vessels, like the carotid arteries. These carry blood to your brain, face, and neck. It might have also spread to your lymph nodes.
  • Stage IVC -- The cancer has spread beyond the thyroid, and to distant sites of the body. It may be in your lungs, bones, and lymph nodes.

The following things apply to everyone who has this type of cancer, no matter their age.

  • Stage I -- The tumor is 2 centimeters or smaller. It’s only in your thyroid.
  • Stage II -- It’s larger than 2 centimeters and found only in your thyroid. Or, it’s any size but has spread to tissues beyond your thyroid. It hasn’t spread to your lymph nodes.
  • Stage III -- It may be smaller or larger than 2 centimeters and may also be in the tissues beyond your thyroid. The cancer is now in the lymph nodes near your voice box and windpipe.
  • Stage IV -- As with follicular and papillary thyroid cancer, stage IV means that the cancer has spread to distant sites in your body, and the letters “A,” “B,” and “C” indicate where it has gone.

This is a fast-growing type of thyroid cancer. For this reason, it’s described only as stage IVA, IVB, or IVC. By the time your doctor finds it, it may have already spread to your neck. Here’s what each stage means:

  • Stage IVA -- Cancer is in your thyroid. It may have spread to nearby lymph nodes.
  • Stage IV -- It has spread beyond your thyroid. It may be in your lymph nodes.
  • Stage IVC -- It has spread to other areas of your body such as your lungs and bones. It may also be in your lymph nodes.