Stage IA includes: (T1a, N0, M0, G1); (T1a, N0, M0, GX). T1a: Tumor invades the lamina propria or muscularis mucosae. N0: No regional lymph node metastasis. M0: No distant metastasis. G1: Well-differentiated. GX: Grade cannot be assessed. (AJCC 8th ed.) [from NCI]