Thyroid Cancer Stages

After someone is diagnosed with thyroid cancer, doctors will try to figure out if 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 use a cancer's stage when talking about survival statistics.

Thyroid cancers range from stages I (1) through IV (4). 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. And within a stage, 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.

How is the stage determined?

The staging system most often used for thyroid cancer is the AJCC (American Joint Committee on Cancer) TNM system, which is based on 3 key pieces of information:

  • The extent (size) of the tumor (T): How large is the cancer? Has it grown into nearby structures?
  • The spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes?
  • The spread (metastasis) to distant sites (M): Has the cancer spread to the distant organs such as the lungs or liver?

The systems described below are the most recent AJCC systems effective January 2018 and applies to differentiated, anaplastic and medullary thyroid cancers.

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced. 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.

The staging system in the table below uses the pathologic stage (also called the surgical stage). It is determined by examining tissue removed during an operation. Sometimes, if surgery is not possible right away or at all, the cancer will be given a clinical stage instead. This is based on the results of a physical exam, biopsy, and imaging tests. The clinical stage will be used to help plan treatment. Sometimes, though, the cancer has spread further than the clinical stage estimates, and might not predict the patient’s outlook as accurately as a pathologic stage.

Cancer staging can be complex, so ask your doctor to explain it to you in a way you understand.

Differentiated (papillary or follicular) thyroid cancer in patients younger than 55

Younger people have a low likelihood of dying from differentiated (papillary or follicular) thyroid cancer. The TNM stage groupings for these cancers take this fact into account. So, all people younger than 55 years with these cancers are stage I if they have no distant spread and stage II if they have distant spread. This table includes patients 55 or older as well as younger than 55. 

AJCC Stage

Age at diagnosis

Stage grouping

Differentiated Thyroid Cancer Stage description*

 

I

 

Younger than 55 years

 

Any T

Any N

M0

 

The cancer is any size (Any T) and might or might not have spread to nearby lymph nodes (Any N).

It has not spread to distant sites (M0).

OR

55 years or older

T1

N0 or NX

M0

The cancer is no larger than 2 cm [0.8 inches] across and confined to the thyroid (T1).

It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

OR

55 years or older

T2

N0 or NX

M0

The cancer is larger than 2 cm [0.8 inches] across but no larger than 4 cm and confined to the thyroid (T2).

It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

 

II

Younger than 55 years

Any T

Any N

M1

The cancer can be any size (Any T). It might or might not have spread to nearby lymph nodes (Any N).

It has spread to other parts of the body, such as distant lymph nodes, internal organs, bones, etc. (M1).

OR

55 years or older

T1

N1

M0

The cancer is no larger than 2 cm [0.8 inches] across and confined to the thyroid (T1).

It has spread to nearby lymph nodes (N1). It has not spread to distant sites (M0).

OR

55 years or older

T2

N1

M0

The cancer is larger than 2 cm [0.8 inches] across but no larger than 4 cm and confined to the thyroid (T2).

It has spread to nearby lymph nodes (N1). It has not spread to distant sites (M0).

OR

55 years or older

T3a or T3b

Any N

M0

The cancer is larger than 4 cm but confined to the thyroid (T3a) or it has grown into the strap muscles around the thyroid (T3b).

It might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant sites (M0).

III

55 years or older

T4a

Any N

M0

The cancer is any size and has grown extensively 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).

It might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant sites (M0).

IVA

55 years or older

T4b

Any N

M0

The cancer is any size and has grown extensively beyond the thyroid gland back toward the spine or into nearby large blood vessels (T4b).

It might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant sites (M0).

IVB

55 years or older

Any T

Any N

M1

The cancer is any size (Any T) and might or might not have spread to nearby lymph nodes (Any N).

It has spread to other parts of the body, such as distant lymph nodes, internal organs, bones, etc. (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. The N categories are described in the table above, except for:
  • NX: Regional lymph nodes cannot be assessed due to lack of information.

Anaplastic (undifferentiated) thyroid cancer

All anaplastic thyroid cancers are considered stage IV, reflecting the poor prognosis for people with this type of cancer.

AJCC Stage

Stage grouping

Anaplastic Thyroid Cancer Stage description*

 

IVA

 

T1, T2 or T3a

N0 or NX

M0

The cancer is any size but confined to the thyroid (T1, T2, or T3a).

It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

IVB

T1, T2 or T3a

N1

M0

The cancer is any size but confined to the thyroid (T1, T2, or T3a). It has spread to nearby lymph nodes (N1).

It has not spread to distant sites (M0).

OR

T3b

Any N

M0

The cancer is any size and has grown into the strap muscles around the thyroid (T3b).

It might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant sites (M0).

OR

T4

Any N

M0

The cancer is any size and has grown extensively 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 or back toward the spine or into nearby large blood vessels (T4). 

It might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant sites (M0).

IVC

Any T

Any N

M1

The cancer is any size (Any T) and might or might not have spread to nearby lymph nodes (Any N).

It has spread to other parts of the body, such as distant lymph nodes, internal organs, bones, etc. (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. The N categories are described in the table above, except for:
  • NX: Regional lymph nodes cannot be assessed due to lack of information.

Medullary thyroid cancer

Age is not a factor in the stage of medullary thyroid cancer.

AJCC Stage

Stage grouping

Medullary Thyroid Cancer Stage description*

 

I

 

T1

N0

M0

The cancer is 2cm (0.8 inches) or smaller and confined to the thyroid (T1).

It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

II

T2

N0

M0

The cancer is larger than 2cm but no more than 4cm across and confined to the thyroid (T2).

It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

OR

T3

N0

M0

The cancer is larger than 4cm and confined the thyroid or any size and growing outside of the thyroid but not involving nearby structures (T3).

It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

III

T1, T2, or T3

N1a

M0

The cancer is any size and might be growing outside of the thyroid but not involving nearby structures (T1, T2, T3).

It has spread to lymph nodes in the neck (pretracheal, paratracheal, prelaryngeal, or upper mediastinal) (N1a) but not to other lymph nodes or to distant sites (M0).

IVA

T4a

Any N

M0

The cancer 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).

It might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant sites (M0).

OR

T1, T2, or T3

N1b

M0

The cancer is any size and might be growing outside of the thyroid but not involving nearby structures (T1, T2, T3).

It has spread to certain lymph nodes in the neck such as cervical or jugular nodes (N1b). It has not spread to distant sites (M0).

IVB

T4b

Any N

M0

The cancer is any size and has grown either back toward the spine or into nearby large blood vessels (T4b).

It might or might not have spread to nearby lymph nodes (Any N). It has not spread to distant sites (M0).

IVC

Any T

Any N

M1

The cancer is any size and might have grown into nearby structures (Any T). 

It might or might not have spread to nearby lymph nodes (Any N). It has spread to distant sites 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. The N categories are described in the table above, except for:
  • NX: Regional lymph nodes cannot be assessed due to lack of information.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, 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.

American Joint Committee on Cancer. Thyroid – Medullary. In: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer; 2017: 891. 

Last Medical Review: December 19, 2017 Last Revised: December 19, 2017

American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.