Thyroid Cancer Staging 

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 minimal extrathyroidal extension (eg, extension to sternothyroid muscle or perithyroid soft tissues)

T4a

Moderately advanced disease; tumor of any size extending beyond the thyroid capsule to invade subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve

T4b

Very advanced disease; tumor invades prevertebral fascia or encases carotid artery or mediastinal vessel

All anaplastic carcinomas are considered stage IV:

T4a

Intrathyroidal anaplastic carcinoma

T4b

Anaplastic carcinoma with gross extrathyroid extension

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

N1

Regional lymph node metastasis

N1a

Metastases to level VI (pretracheal, paratracheal, and prelaryngeal/Delphian lymph nodes)

N1b

Metastases to unilateral, bilateral, or contralateral cervical (levels I, II, III, IV, or V) or retropharyngeal or superior mediastinal lymph nodes (level VII)

Distant metastasis (M)

M0

No distant metastasis is found

M1

Distant metastasis is present

Stage grouping

Separate stage groupings are recommended for papillary or follicular (differentiated), medullary, and anaplastic (undifferentiated) carcinoma

Papillary and follicular thyroid cancer (age < 45y):

Stage

T

N

M

I

Any T

Any N

M0

II

Any T

Any N

M1

Papillary and follicular; differentiated (age ≥ 45y):

Stage

T

N

M

I

T1

N0

M0

II

T2

N0

M0

III

T3

N0

M0

IVA

T1-3

N1a

M0

T4a

N1b

M0

IVB

T4b

Any N

M0

IVC

Any T

Any N

M1

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

Stage

T

N

M

IVA

T4a

Any N

M0

IVB

T4b

Any N

M0

IVC

Any T

Any N

M1

Medullary carcinoma (all age groups):

Stage

T

N

M

I

T1

N0

M0

II

T2, T3

N0

M0

III

T1-T3

N1a

M0

IVA

T4a

N0

M0

T4a

N1a

M0

T1

N1b

M0

T2

N1b

M0

T3

N1b

M0

T4a

N1b

M0

T4a

N0, N1b

M0

T1-T4a

N1b

M0

IVB

T4b

Any N

M0

IVC

Any T

Any N

M1