Staging means finding out how far thyroid cancer has spread in your body. Physicians group thyroid cancer into stages I (1) through IV (4), with stage I being the least advanced and stage IV being the most advanced.
When your Fred Hutch Cancer Center team designs your treatment plan, they will consider the stage of your thyroid cancer along with many other factors. The stage is an important part of choosing which treatments are right for you.
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Thyroid Cancer Stages
The stage of thyroid cancer is determined based on the TNM system. The stage depends on:
- Tumor (T): The size of the main tumor and any spread of cancer into nearby tissue
- Nodes (N): The number of nearby lymph nodes where cancer has spread
- Metastasis (M): If cancer has spread (metastasized) to other parts of the body
In the TNM system, there will be a symbol after each letter to give details; for example, T1N0M0. In T1, the 1 indicates the size of the tumor (small). In N0, the 0 means there’s no sign of cancer in nearby lymph nodes. In M0, the 0 means cancer hasn’t spread to distant parts of the body. If you would like to know the stage of your cancer in the TNM system, ask your Fred Hutch care team.
There are slightly different staging systems for papillary, follicular, anaplastic, medullary and Hurthle cell thyroid cancers.
In people younger than 55 years, papillary and follicular thyroid cancers are divided into two stages.
- Stage I if the cancer has not spread to distant parts of the body
- Stage II if the cancer has spread to distant parts of the body
For people 55 and older, staging is more complex.
Stage I (1)
- The main tumor is no larger than 2 centimeters (0.8 inches) across and is still just in the thyroid (T1).
- The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
OR
- The main tumor is larger than 2 cm (0.8 inches) across but no larger than 4 cm and is still just in the thyroid (T2).
- The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
Stage II (2)
- The main tumor is no larger than 2 cm (0.8 inches) across and is still just in the thyroid (T1).
- The cancer has spread to nearby lymph nodes (N1). It has not spread to distant parts of the body (M0).
OR
- The main tumor is larger than 2 cm (0.8 inches) across but no larger than 4 cm and is still just in the thyroid (T2).
- The cancer has spread to nearby lymph nodes (N1). It has not spread to distant parts of the body (M0).
OR
- The main tumor is larger than 4 cm across but is still just in the thyroid (T3a) or it has grown into the strap muscles around the thyroid (T3b).
- The cancer might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant parts of the body (M0).
Stage III (3)
- The main tumor can be any size but it has grown beyond the thyroid gland into nearby tissues of the neck, such as the larynx (voice box), trachea (windpipe), esophagus (tube connecting the throat to the stomach), or the nerve to the larynx (T4a).
- The cancer might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant parts of the body (M0).
Stage IV (4) A
- The main tumor can be any size but it has grown extensively beyond the thyroid gland back toward the spine or into nearby large blood vessels (T4b).
- The cancer might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant parts of the body (M0).
Stage IV (4) B
- The main tumor can be any size, and it might or might not have grown outside the thyroid (Any T) or have spread to nearby lymph nodes (Any N).
- The cancer has spread to other parts of the body, such as the lungs, bones, or brain. (M1).
Age is not a factor in staging medullary thyroid cancer.
Stage I (1)
- The main tumor is no more than 2 centimeters (0.8 inches) across and is still just in the thyroid (T1).
- The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
Stage II (2)
- The main tumor is larger than 2 cm but no more than 4 cm across and is still just in the thyroid (T2).
- The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
OR
- The main tumor is larger than 4 cm across and is still just in the thyroid, or it is any size but is growing into the strap muscles around the thyroid (T3).
- The cancer has not spread to nearby lymph nodes (N0) or to distant sites (M0).
Stage III (3)
- The main tumor is any size and might be growing outside of the thyroid, but it has not grown beyond the strap muscles around the thyroid (T1, T2, T3).
- The cancer has spread to lymph nodes in the neck (N1a), but it has not spread to other lymph nodes or to distant parts of the body (M0).
Stage IV (4) A
- The main tumor is any size and has grown beyond the thyroid gland into nearby tissues of the neck, such as the larynx (voice box), trachea (windpipe), esophagus (tube connecting the throat to the stomach), or the nerve to the larynx (T4a).
- The cancer might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant parts of the body (M0).
OR
- The main tumor is any size and might be growing outside of the thyroid, but it has not grown beyond the strap muscles around the thyroid (T1, T2, T3).
- The cancer has spread to lymph nodes in the neck farther away from the thyroid, such as cervical or jugular nodes (N1b). It has not spread to distant parts of the body (M0).
Stage IV (4) B
- The main tumor is any size and has grown either back toward the spine or into nearby large blood vessels (T4b).
- The cancer might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant parts of the body (M0).
Stage IV (4) C
- The main tumor is any size and might have grown into nearby structures (Any T).
- The cancer might or might not have spread to nearby lymph nodes (Any N). It has spread to distant parts of the body such as the liver, lung, bone, or brain (M1).
- The main tumor measures between 2 and 4 centimeters (about half an inch to 1.5 inches). It hasn’t spread outside the thyroid.
Stage II (2)
- The main tumor measures between 2 and 4 centimeters, and the cancer is in nearby lymph nodes.
Stage III (3)
- The main tumor is in nearby neck tissues, like the voice box (larynx), windpipe (trachea) or food pipe (esophagus).
Stage IV (4)
- The main tumor is spreading to more areas. It may be moving toward the spine and nearby large blood vessels, bones, brain or lungs.
How to Know Your Thyroid Cancer Stage
As part of your diagnosis with thyroid cancer, you will have imaging scans and other tests, like biopsies, to tell if the cancer has spread and where. In a biopsy, a tissue sample is removed with a needle and a pathologist checks to see if it contains cancer cells.
If you have had staging tests and you already know the stage of your cancer before you come to Fred Hutch, we will look at the test results before your first appointment. If you have not had these tests, we will talk with you about which tests you need, why, how to get them and when you can expect results.
Causes of Thyroid Cancer
The exact cause of thyroid cancer is not known. But studies show that certain factors are linked to increased risk. Some of these risk factors are things you can’t change, such as having a family history of thyroid cancer. Other factors relate to your lifestyle, so you may be able to change them. For example, having excess body weight or too much or too little iodine in your diet raises thyroid cancer risk.