5
Table 2. AJCC TNM Classification System for Differentiated
Thyroid Carcinoma
Primary Tumor (T)
TX Size not assessed, limited to the thyroid
T1 T1a ≤1 cm, limited to the thyroid
T1b >1 cm but ≤2 cm, limited to the thyroid
T2 >2 cm but ≤4 cm, limited to the thyroid
T3 >4 cm, limited to the thyroid, or any tumor with minimal
extrathyroid extension
T4 T4a Tumor extends beyond the thyroid capsule to invade
subcutaneous so tissues, larynx, trachea, esophagus, or
recurrent laryngeal nerve
T4b Tumor invades prevertebral fascia or encases carotid artery or
mediastinal vessels
Lymph Nodes (N)
NX Regional lymph nodes not assessed
N0 No regional lymph node metastasis
N1 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 Metastasis (M)
MX Distant metastasis not assessed
M0 No distant metastasis
M1 Distant metastasis
Pediatric patients are considered to have Stage II disease if distant metastases are identified (M1);
otherwise, all pediatric patients are considered to have Stage I disease.
Used with the permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois.
e original source for this material is the AJCC Cancer Staging Manual, 7th Edition (2010)
published by Springer Science and Business Media LLC, www.springer.com.
