Stage I is divided into stage IA and stage IB, depending on where the cancer has spread. In stage IA, cancer has spread completely through the mucosal (innermost) layer of the stomach wall. In stage IB, cancer has spread completely through the mucosal (innermost) layer of the stomach wall and is found in up to 6 lymph nodes near the tumor, or has spread to the muscularis (middle) layer of the stomach wall.