1. Thyroid Thyroid gland. Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

2. Thyroid T1 is defined as tumor 2 cm or less in greatest dimension limited to the thyroid. T1a is defined as tumor 1 cm or less, limited to the thyroid. T1b is defined as tumor more than 1 cm but not more than 2 cm in greatest dimension, limited to the thyroid. Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

3. Thyroid T2 is defined as tumor more than 2 cm but not more than 4 cm in greatest dimension limited to the thyroid. Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

4. Thyroid Two views of T3: on the left, a tumor more than 4 cm in greatest dimension limited to the thyroid; on the right, a tumor with minimal extrathyroid extension (to either sternothyroid muscle or perithyroid soft tissues). Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

5. Thyroid T4a is defined as moderately advanced disease, a tumor of any size extending beyond the thyroid capsule to invade subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve. Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

6. Thyroid Cross-sectional diagram of three different parameters of T4a: tumor invading subcutaneous soft tissues; tumor invading trachea; tumor invading esophagus. Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

7. Thyroid T4b is defined as very advanced disease, tumor invading prevertebral fascia or encases carotid artery or mediastinal vessels. Cross-sectional diagram of two different parameters of T4b: tumor encases carotid artery; tumor invades vertebral body. Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

8. Thyroid N1a is defined as metastasis to Level VI (pretracheal, paratracheal, and prelaryngeal/Delphian lymph nodes). Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer

9. Thyroid N1b is defined as metastasis to unilateral, bilateral, or contralateral cervical (Levels I, II, III, IV, or V) or retropharyngeal or superior mediastinal lymph nodes (Level VII). Compton, C.C., Byrd, D.R., et al., Editors. AJCC CancerStaging Atlas, 2nd Edition. New York: Springer, 2012. ©American Joint Committee on Cancer