Cancer has formed in the inside lining of the mucosa (innermost layer) of the stomach wall. Stage I is divided into stages IA and IB, depending on where the cancer has spread. In stage IA, cancer may have spread into the submucosa (layer of tissue next to the mucosa) of the stomach wall. In stage IB, cancer (1) may have spread into the submucosa (layer of tissue next to the mucosa) of the stomach wall and is found in 1 or 2 lymph nodes near the tumor; or (2) has spread to the muscle layer of the stomach wall.