Thyroid Cancer Stages
If you are diagnosed with thyroid cancer, doctors will try to figure out whether it has spread, and if so, how far. This process is called staging.
The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also often use a cancer's stage when talking about survival statistics.
How is the stage determined?
The staging system most often used for thyroid cancer is the AJCC (American Joint Committee on Cancer) TNM system. The systems below are the most recent AJCC systems. They apply to differentiated, anaplastic, and medullary thyroid cancers.
T, N, and M categories
The AJCC TNM system is based on 3 key pieces of information:
- The size and extent of the main (primary) tumor (T): How large is the tumor? Has it grown into nearby structures?
- Spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes?
- Spread (metastasis) to distant sites (M): Has the cancer spread to distant organs such as the lungs or liver?
Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced.
Stage grouping (I-IV)
Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. For more information, see Cancer Staging.
Thyroid cancer stages range from I (1) through IV (4), sometimes with a letter after the number. As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. Within a stage (1-4), an earlier letter means a lower stage.
Although each person’s cancer experience is unique, cancers with similar stages tend to have a similar outlook and are often treated in much the same way.
Determining thyroid cancer stage
The stage of a thyroid cancer can be determined in 2 ways:
- Clinical stage: The clinical stage is based on the results of physical exams, imaging tests, and any biopsies that have been done (see Tests for Thyroid Cancer). The clinical stage can be helpful in determining treatment options.
- Pathological stage: If surgery is done, the pathological stage (also called the surgical stage) can be determined. This is based on the information above, as well as what is learned about the cancer by examining tissue removed during the operation.
The clinical and pathological stages for thyroid cancer are usually similar, but it’s possible that the stage might change after surgery is done. For example, surgery might show that the cancer has spread farther than what was seen on imaging tests. If this is the case, the pathological stage might be higher than the clinical stage.
There are slightly different staging systems for differentiated (papillary or follicular), anaplastic, and medullary thyroid cancers, so they are described in separate tables below.
Cancer staging can be complex. You can always ask your cancer care team to explain your stage in a way you understand.
Differentiated (papillary or follicular) thyroid cancer
Younger people with differentiated (papillary or follicular) thyroid cancer tend to have a better outlook than people who are older. The TNM stage groupings for these cancers take this into account.
For people younger than 55
In people younger than 55 years, differentiated thyroid cancers are divided into only 2 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 aged 55 and older
Staging is more complex for people who are 55 years old or older, as seen in the table below.
AJCC Stage |
Stage grouping |
Differentiated Thyroid Cancer Stage description* |
|
I
|
T1 N0 or NX M0 |
The main tumor is no larger than 2 centimeters (cm) [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 |
|||
T2 N0 or NX M0 |
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). |
||
II |
T1 N1 M0 |
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 |
|||
T2 N1 M0 |
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 |
|||
T3a or T3b Any N M0 |
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). |
||
III |
T4a Any N M0 |
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). |
|
IVA |
T4b Any N M0 |
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). |
|
IVB |
Any T Any N M1 |
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). |
|
* The following additional categories are not listed on the table above:
- TX: Main tumor cannot be assessed due to lack of information.
- T0: No evidence of a primary tumor.
- NX: Regional lymph nodes cannot be assessed due to lack of information.
Anaplastic (undifferentiated) thyroid cancer
All anaplastic thyroid cancers are considered stage IV, even when they haven’t spread, because these cancers often spread quickly and can be hard to treat.
AJCC Stage |
Stage grouping |
Anaplastic Thyroid Cancer Stage description* |
IVA
|
T1, T2 or T3a N0 or NX M0 |
The main tumor can be any size, but it is still just in the thyroid (T1, T2, or T3a). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0). |
IVB |
T1, T2 or T3a N1 M0 |
The main tumor can be any size, but it is still just in the thyroid (T1, T2, or T3a). The cancer has spread to nearby lymph nodes (N1). It has not spread to distant parts of the body (M0). |
OR |
||
T3b Any N M0 |
The main tumor can be any size, but 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). |
|
OR |
||
T4 Any N M0 |
The main tumor can be any size, but it has grown beyond the thyroid 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 ,or it has grown back toward the spine or into nearby large blood vessels (T4). 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). |
|
IVC |
Any T Any N M1 |
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). |
* The following additional categories are not listed on the table above:
- TX: Main tumor cannot be assessed due to lack of information.
- T0: No evidence of a primary tumor.
- NX: Regional lymph nodes cannot be assessed due to lack of information.
Medullary thyroid cancer
Age is not a factor in the staging of medullary thyroid cancer.
AJCC Stage |
Stage grouping |
Medullary Thyroid Cancer Stage description* |
I
|
T1 N0 M0 |
The main tumor is no more than 2 centimeters (cm) [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). |
II |
T2 N0 M0 |
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 |
||
T3 N0 M0 |
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). |
|
III |
T1, T2, or T3 N1a M0 |
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 (pretracheal, paratracheal, prelaryngeal, or upper mediastinal nodes) (N1a), but it has not spread to other lymph nodes or to distant parts of the body (M0). |
IVA |
T4a Any N M0 |
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 |
||
T1, T2, or T3 N1b M0 |
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). |
|
IVB |
T4b Any N M0 |
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). |
IVC |
Any T Any N M1 |
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 following additional categories are not listed on the table above:
- TX: Main tumor cannot be assessed due to lack of information.
- T0: No evidence of a primary tumor.
- NX: Regional lymph nodes cannot be assessed due to lack of information.
- Written by
- References
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
American Joint Committee on Cancer. Thyroid – Differentiated and Anaplastic. In: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer; 2017: 873-890.
American Joint Committee on Cancer. Thyroid – Medullary. In: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer; 2017: 891-901.
Last Revised: August 23, 2024
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
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