Stomach cancer is a type of cancer that begins in the stomach. It is a relatively rare cancer, accounting for only 1-2% of all cancers diagnosed each year in the United States. The most common symptoms of stomach cancer include nausea, vomiting, and abdominal pain. In advanced cases, the cancer may spread to other parts of the body, such as the liver or lungs. Treatment options for stomach cancer include surgery, chemotherapy, and radiation therapy.