Table 2.

AJCC TNM staging for thyroid cancer: T staging of DTC and MTC

T stage	Size in greatest dimension	Presence of invasion
T1	≤2 cm	No extracapsular invasion
T2	>2 cm, ≤4 cm	No extracapsular invasion
T3	>4 cm	OR minimal extrathyroid extension (e.g., extension to sternothyroid muscle or perithyroid soft tissues)
T4a	Any size	Beyond the thyroid capsule to invade subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve
T4b	Any size	Prevertebral fascia or encases carotid artery or mediastinal vessels

Patients with DTC <45 years of age can only be staged as stage I or II; stage II has metastatic disease (M1).

For patients with DTC ≥45 years and MTC at any age, M1 determines stage IVc.

All anaplastic carcinomas are T4a, confined to thyroid, or T4b, invasion beyond the capsule. Therefore, all are Stage IV.