Common symptoms of stomach cancer include unintentional weight loss, nausea, vomiting, poor appetite and abdominal pain, according to the American Cancer Society. Individuals may notice swelling in the abdomen and feel full when consuming small portions of food. They may also develop heartburn and anemia.
Scientists don't know the cause of stomach cancer, also known as gastric cancer, but the disease progresses as the rapid growth of mutated cells produces tumors that overwhelm nearby organs, Mayo Clinic states. Individuals who consume high amounts of sodium or smoked food and inadequate amounts of fruits and vegetables have a higher risk of developing stomach cancer. While factors such as smoking, polyps, pernicious anemia and H. pylori infection can also increase the risk, cases of stomach cancer are not common in the United States.
The most common forms of stomach cancer are adenocarcinoma, carcinoid tumors, lymphoma and gastrointestinal stromal tumors, or GIST, the American Cancer Society notes. Adenocarcinoma grows in the stomach's mucosal lining and accounts for approximately 90 to 95 percent of gastric cancers. Carcinoid tumors affect hormone-producing cells and are only present in about 3 percent of stomach cancer patients. Lymphomas in immune system cells make up about 4 percent of stomach cancers, while GIST growths are rare and form in interstitial tissue.