5
Table 3A. American Joint Committee on Cancer TNM
Classification (Thyroid Cancer)
Note: All categories may be subdivided: s=solitary tumor and
m=multifocal tumor (the largest determines the classification).
Primary tumor (T)
T0 No evidence of primary tumor
T1 Tumor ≤2 cm in greatest dimension, limited to the thyroid
T1a Tumor ≤1 cm, limited to the thyroid
T1b Tumor 1-2 cm, in greatest dimension, limited to the thyroid
T2 Tumor 2-4 cm, in greatest dimension, limited to the thyroid
T3 Tumor 4 cm in greatest dimension limited to the thyroid, or any tumor with
minimal extrathyroid extension (e.g., extension to sternothyroid muscle or
perithyroid so tissues)
T4a Moderately advanced disease: Tumor of any size extending beyond the
thyroid capsule to invade subcutaneous so tissues, larynx, trachea,
esophagus, or recurrent laryngeal nerve
T4b Very advanced disease: Tumor invades prevertebral fascia or encases carotid
artery or mediastinal vessels
Regional Lymph Nodes (N)
Regional lymph nodes are those in the central and lateral cervical compartments and the
upper mediastinum
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Regional lymph node metastasis
N1a Metastasis to Level VI (pretracheal, paratracheal, and prelaryngeal/Delphian
lymph nodes)
N1b Metastasis to unilateral, bilateral, or contralateral cervical (Levels I, II, III,
IV, or V) or retropharyngeal or superior mediastinal lymph nodes (Level VII)
Distant metastases (M)
M0 No distant metastasis
M1 Distant metastasis
