Stomach cancer is a disease in which malignant (cancer) cells form in the lining of the stomach.

The stomach is a J-shaped organ in the upper abdomen. It is part of the digestive system, which processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) in foods that are eaten and helps pass waste material out of the body. Food moves from the throat to the stomach through a hollow, muscular tube called the esophagus. After leaving the stomach, partly-digested food passes into the small intestine and then into the large intestine.

The stomach and esophagus are part of the upper digestive system.

The wall of the stomach is made up of 3 layers of tissue: the mucosal (innermost) layer, the muscularis (middle) layer, and the serosal (outermost) layer. Stomach cancer begins in the cells lining the mucosal layer and spreads through the outer layers as it grows.

See the following PDQ summaries for more information about stomach cancer:

• Stomach (Gastric) Cancer Prevention
• Gastric Cancer Treatment

Stomach cancer is less common in the United States than in the developing world.

Stomach cancer is the fourteenth most frequent cause of cancer death in the United States. This type of cancer is much more common in many parts of Europe, Asia, and Central and South America, and is a major cause of death in the developing world.

Stomach cancer rates in the United States have greatly decreased since 1930. The reasons for this are not known, but may have to do with better food storage or changes in the diet, such as lower salt intake.

Older age and certain chronic conditions increase the risk of developing stomach cancer.

Anything that increases the chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for stomach cancer include the following:

• Having any of the following medical conditions:
  • Helicobacter pylori (H. pylori) infection of the stomach.
  • Chronic gastritis (inflammation of the stomach).
  • Pernicious anemia.
  • Intestinal metaplasia (a condition in which the normal stomach lining is replaced with the cells that line the intestines).
  • Familial adenomatous polyposis (FAP) or gastric polyps.
• Being older or male.
• Eating a diet high in salted, smoked foods and low in fruits and vegetables.
• Eating foods that have not been prepared or stored properly.
• Smoking cigarettes.
• Having a mother, father, sister, or brother who has had stomach cancer.