Stage I includes: Under 55 years: Any T, Any N, M0. 55 years and older: (T1, N0/NX, M0); (T2, N0/NX, M0). T1: Tumor measuring 2 cm or less in greatest dimension limited to the thyroid. T2: Tumor measuring more than 2 cm but 4 cm or less in greatest dimension limited to the thyroid. N0: No evidence of locoregional lymph node metastasis. NX: Regional lymph nodes cannot be assessed. M0: No distant metastasis. (from AJCC 8th Ed.) [from NCI]