AJCC 7th Edition TNM Score for Papillary or Follicular Well-Differentiated Thyroid Cancer (21)

Primary tumor (T)
T1Tumor ≤ 2 cm, limited to thyroid; T1a: tumor ≤ 1 cm (microcarcinoma);T1b: tumor > 1 cm but ≤ 2 cm
T2Tumor > 2 cm but ≤ 4 cm, limited to thyroid
T3Tumor > 4 cm, limited to thyroid, or any tumor with minimal extrathyroid extension; for example, extension to sternothyroid muscle or perithyroid soft tissues
T4Advanced disease: T4a: tumor of any size extending beyond thyroid capsule to invade subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve; T4b: tumor invades prevertebral fascia or encases carotid artery or mediastinal vessels
Regional nodes (N)
N0No regional lymph node metastasis
N1Regional lymph node metastasis; N1a: metastasis to central neck compartment (cervical level VI); N1b: metastasis to unilateral, bilateral, or contralateral lateral neck compartments (cervical levels I, II, III, IV, or V) or retropharyngeal or superior mediastinal lymph nodes (cervical level VII)
Distant metastases (M)
M0No distant metastasis
M1Distant metastasis