Light micrograph of anaplastic cancer of the stomach. Most of the cells seen here are cancerous, having large, irregular shapes and multiple nuclei (darker purple). Stomach (or gastric) cancer develops from the cells that line the interior wall of the stomach. It is a fairly common cancer linked to diet and other environmental factors. Stomach cancer must be detected before it spreads beyond the stomach lining. Gastrectomy (removal of all or part of the stomach) is a common treatment, but in most cases the cancer is too advanced to be operable by the time it is diagnosed.