The stomach wall has three linings (inner, middle, and outer). Cancer of the stomach, also called gastric cancer, is a disease in which malignant (cancer) cells grow from the inner lining of the stomach. Stomach cancer can develop in any part of the stomach and then may spread throughout the stomach and to other organs. Stomach cancers are classified according to the type of tissue from which they originate. The most common type of stomach cancer is adenocarcinoma, which starts in the glandular tissue of the stomach, and accounts for 95% of all stomach cancers.