Table 3. Definitions of Differentiated TNM Stage II for Papillary and Follicular Thyroid Carcinomaa

StageTbNMDescriptionIllustration
Age at diagnosis is <55 years:
IIAny T, Any N, M1TX = Primary tumor cannot be assessed.
Stage II papillary and follicular thyroid cancer in patients younger than 55 years; 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 gland, 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.
Age at diagnosis is ≥55 years:
IIT1, N1, M0T1 = Tumor ≤2 cm in greatest dimension, limited to the thyroid.
Stage II papillary and follicular thyroid cancer (1) in patients 55 years and older; drawing shows cancer in the thyroid gland and nearby lymph nodes. The tumor is 4 centimeters or smaller. An inset shows 4 centimeters is about the size of a walnut. Also shown are the larynx and trachea.
Stage II papillary and follicular thyroid cancer (2) in patients 55 years and older; drawing shows cancer in the thyroid gland and the tumor is larger than 4 centimeters. An inset shows 4 centimeters is about the size of a walnut. Also shown are the lymph nodes, larynx, and trachea.
Stage II papillary and follicular thyroid cancer (3) in patients 55 years and older; drawing shows cancer in the thyroid gland and nearby muscles in the neck. Also shown are the larynx and trachea.
–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.
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.
T2, N1, M0T2 = Tumor >2 cm but ≤4 cm in greatest dimension, limited to the thyroid.
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.
T3a/T3b, Any N, M0–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.
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.

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®)

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