Thyroid Cancer Staging 

Updated: Sep 16, 2019
  • Author: Eric J Lentsch, MD; Chief Editor: Neetu Radhakrishnan, MD  more...
  • Print

TNM Classification for Thyroid Cancer

The American Joint Committee on Cancer (AJCC) used different tumor-node-metastasis (TNM) classification for differentiated and anaplastic thyroid cancer and for medullary thyroid cancer, as outlined below. [1, 2, 3]

Table 1. TNM Classification for Differentiated and Anaplastic Thyroid Cancer (Open Table in a new window)

Primary tumor (T)

TX

Primary tumor cannot be assessed

T0

No evidence of primary tumor is found

T1

Tumor size ≤ 2 cm in greatest dimension and is limited to the thyroid

T1a

Tumor ≤ 1 cm, limited to the thyroid

T1b

Tumor > 1 cm but ≤ 2 cm in greatest dimension, limited to the thyroid

T2

Tumor size > 2 cm but ≤ 4 cm, limited to the thyroid.

T3

Tumor size > 4 cm, limited to the thyroid or any tumor with gross extrathyroidal extension invading only strap muscles

T3a Tumor size > 4 cm, limited to the thyroid 
T3b Any size tumor with gross extrathyroidal extension invading only strap muscles (eg, extension to sternothyroid muscle or perithyroid soft tissues)

T4a

Any size tumor with gross extrathyroidal extension invading subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve

T4b

Any size tumor with gross extrathyroidal extension invading prevertebral fascia or encasing the carotid artery or mediastinal vessels

All categories may be subdivided: (s) solitary tumor and (m) multifocal tumor (the largest determines classification)

Regional lymph nodes (N)

Regional lymph nodes are the central compartment, lateral cervical, and upper mediastinal lymph nodes:

NX

Regional nodes cannot be assessed

N0

No regional lymph node metastasis

N0a One or more cytologically or histologically confirmed benign lymph nodes
N0b No radiologic or clinical evidence of locoregional lymph node metastasis

N1

Regional lymph node metastasis

N1a

Metastases to level VI or VI (pretracheal, paratracheal, or prelaryngeal/Delphian or upper mediastinal) lymph nodes

N1b

Metastases to unilateral, bilateral, or contralateral neck lymph nodes (levels I, II, III, IV, or V) or retropharyngeal lymph nodes

Distant metastasis (M)

M0

No distant metastasis is found

M1

Distant metastasis is present

Table 2. TNM Classification for Medullary Thyroid Cancer (Open Table in a new window)

Primary tumor (T)

TX

Primary tumor cannot be assessed

T0

No evidence of primary tumor is found

T1

Tumor size ≤ 2 cm in greatest dimension and is limited to the thyroid

T1a

Tumor ≤ 1 cm, limited to the thyroid

T1b

Tumor > 1 cm but ≤ 2 cm in greatest dimension, limited to the thyroid

T2

Tumor size > 2 cm but ≤ 4 cm, limited to the thyroid.

T3

Tumor size > 4 cm, limited to the thyroid or any tumor with gross extrathyroidal extension invading only strap muscles

T3a Tumor size > 4 cm, limited to the thyroid 
T3b Any size tumor with gross extrathyroidal extension invading only strap muscles (eg, extension to sternothyroid muscle or perithyroid soft tissues)

T4a

Moderately advanced disease; Any size tumor with gross extrathyroidal extension invading subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve

T4b

Very advanced disease; Any size tumor with extension toward the spine or into nearby large blood vessels, gross extrathyroidal extension invading prevertebral fascia or encasing the carotid artery or mediastinal vessels

 

Regional lymph nodes (N)

Regional lymph nodes are the central compartment, lateral cervical, and upper mediastinal lymph nodes:

NX

Regional nodes cannot be assessed

N0

No regional lymph node metastasis

N0a One or more cytologically or histologically confirmed benign lymph nodes
N0b No radiologic or clinical evidence of locoregional lymph node metastasis

N1

Regional lymph node metastasis

N1a

Metastases to level VI or VI (pretracheal, paratracheal, or prelaryngeal/Delphian or upper mediastinal) lymph nodes; can be unilateral or bilateral disease

N1b

Metastases to unilateral, bilateral, or contralateral neck lymph nodes (levels I, II, III, IV, or V) or retropharyngeal lymph nodes

Distant metastasis (M)

M0

No distant metastasis is found

M1

Distant metastasis is present

Table3. Stage grouping (Open Table in a new window)

Stage grouping

Differentiated, medullary, and anaplastic carcinoma have separte stage groupings

Differentiated (age < 55y):

Stage

T

N

M

I

Any T

Any N

M0

II

Any T

Any N

M1

Differentiated (age ≥ 55y):

Stage

T

N

M

I

T1

N0/NX

M0

T2 N0/NX M0

II

T1

N1

M0

T2 N1 M0
T3a/T3b Any N M0

III

T4a

Any N

M0

IVA

T4b

Any N

M0

IVB

Any T

Any N

M1

Anaplastic carcinoma (all anaplastic carcinomas are considered stage IV):

Stage

T

N

M

IVA

T1-T3a

N0/NX

M0

IVB

T1-T3a

Any N

M0

T3b Any N M0
T4 Any N M0

IVC

Any T

Any N

M1

Medullary carcinoma:

Stage

T

N

M

I

T1

N0

M0

II

T2, T3

N0

M0

III

T1-T3

N1a

M0

IVA

T4a

Any N

M0

T1-T3

N1b

M0

IVB

T4

N0

M0

IVC

Any T

Any N

M1