Stage I includes: IA (T1a, N0, M0, G1, GX); (T1b, N0, M0, G1, GX); IB (T2a, N0, M0, G1, GX); (T2b, N0, M0, G1, GX). T1a: Superficial tumor 5 cm or less in greatest dimension. T1b: Deep tumor 5 cm or less in greatest dimension. T2a: Superficial tumor more than 5 cm in greatest dimension. T2b: Deep tumor more than 5 cm in greatest dimension. N0: No regional lymph node metastasis. M0: No distant metastasis. G1: Grade 1. GX: Grade cannot be assessed. (AJCC 7th ed.) [from NCI]