Table 5. Definitions of Differentiated TNM Stages IVA and IVB for Papillary and Follicular Thyroid Carcinomaa

StageTbNMDescriptionIllustration
Age at diagnosis is ≥55 years:
IVAT4b, Any N, M0 –T4b = Gross extrathyroidal extension invading prevertebral fascia or encasing the carotid artery or mediastinal vessels from a tumor of any size.
Stage IVA papillary and follicular thyroid cancer in patients 55 years and older; drawing shows cancer has (a) spread to tissue in front of the spine, (b) surrounded the common carotid artery, and (c) surrounded the blood vessels in the area between the lungs. Also shown are the thyroid gland, trachea, and lymph nodes.
NX = Regional lymph nodes cannot be assessed.
N0 = No evidence of locoregional 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 = Metastasis to regional nodes.
–N1a = Metastasis to level VI or VII (pretracheal, paratracheal, or prelaryngeal/Delphian, or upper mediastinal) lymph nodes. This can be unilateral or bilateral disease.
–N1b = Metastasis to unilateral, bilateral, or contralateral cervical neck lymph nodes (levels I, II, III, IV, or V) or retropharyngeal lymph nodes.
M0 = No distant metastasis.
IVBAny T, Any N, M1TX = Primary tumor cannot be assessed.
Stage IVB papillary and follicular thyroid cancer in patients 55 years and older; drawing shows other parts of the body where thyroid cancer may spread, including the lung and bone. An inset shows cancer cells spreading from the thyroid, through the blood and lymph system, to another part of the body where metastatic cancer has formed.
T0 = No evidence of primary tumor.
T1 = Tumor ≤2 cm in greatest dimension, limited to the thyroid.
–T1a = Tumor ≤1 cm in greatest dimension, limited to the thyroid.
–T1b = Tumor >1 cm but ≤2 cm in greatest dimension, limited to the thyroid.
T2 = Tumor >2 cm but ≤4 cm in greatest dimension, limited to the thyroid.
T3 = Tumor >4 cm limited to the thyroid, or gross extrathyroidal extension invading only strap muscles.
–T3a = Tumor >4 cm limited to the thyroid.
–T3b = Gross extrathyroidal extension invading only strap muscles (sternohyoid, sternothyroid, thyrohyoid, or omohyoid muscles) from a tumor of any size.
T4 = Includes gross extrathyroidal extension beyond the strap muscles.
–T4a = Gross extrathyroidal extension invading subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve from a tumor of any size.
–T4b = Gross extrathyroidal extension invading prevertebral fascia or encasing the carotid artery or mediastinal vessels from a tumor of any size.
NX = Regional lymph nodes cannot be assessed.
N0 = No evidence of locoregional 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 = Metastasis to regional nodes.
–N1a = Metastasis to level VI or VII (pretracheal, paratracheal, or prelaryngeal/Delphian, or upper mediastinal) lymph nodes. This can be unilateral or bilateral disease.
–N1b = Metastasis to unilateral, bilateral, or contralateral cervical neck lymph nodes (levels I, II, III, IV, or V) or retropharyngeal lymph nodes.
M1 = Distant metastasis.

M = distant metastasis; N = regional lymph nodes; T = primary tumor.

aReprinted with permission from AJCC: Thyroid--Differentiated and Anaplastic Carcinoma. In: Amin, MB, Edge Sb, Greene FL et al., eds.: AJCC Cancer Staging Manual. 8th ed. New York, NY: Springer, 2017, pp 873–90.

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

From: Thyroid Cancer Treatment (Adult) (PDQ®)

Cover of PDQ Cancer Information Summaries
PDQ Cancer Information Summaries [Internet].
Bethesda (MD): National Cancer Institute (US); 2002-.
Copyright Notice

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.