Stage I includes: IA: (T1, N0, M0); IB: (T2, N0, M0). T1: Tumor measuring 2 cm or less in greatest dimension. T2: Tumor measuring more than 2 cm and 4 cm or less in greatest dimension. N0: No regional lymph node metastasis. M0: No distant metastasis. (AJCC 8th ed.) [from
NCI]