Stage IB includes: (T1a, N0, M0, G2-3, Tumor location: Any); (T1b, N0, M0, G1-3, Tumor location: Any); (T1b, N0, M0, GX, Tumor location: Any); (T2, N0, M0, G1, Tumor location: Any). T1a: Tumor invades the lamina propria or muscularis mucosae. T1b: Tumor invades the submucosa. T2: Tumor invades the muscularis propria. N0: No regional lymph node metastasis. M0: No distant metastasis. G1: Well-differentiated. GX: Grade cannot be assessed. G2: Moderately differentiated. G3: Poorly differentiated, undifferentiated. (AJCC 8th ed.) [from NCI]