Upper Gastrointestinal System
The stomach is a large organ in the upper abdomen that plays an important role in digesting food and helping the body absorb nutrients.
Most cases of stomach cancer develop slowly in the lining of the organ over the course of several years. Because the illness typically does not cause symptoms until it is in its later stages, many people are not diagnosed until the disease is advanced.
According to the American Cancer Society, approximately 22,000 people in the United States are diagnosed with stomach cancer each year. This is a relatively low figure compared to other parts of the world; stomach cancer is far more common in developing countries throughout Asia, Central and Eastern Europe, and South America, possibly due to various diet, lifestyle, and environmental factors.
Types of Stomach Cancer
Most stomach cancers (up to 95 percent) are adenocarcinomas, which are tumors that form in the glandular tissues that make up the lining of the stomach.
There are three main types:
- Non-cardia (distal) stomach cancer is a type of adenocarcinoma thought to be related to long periods of inflammation and irritation in the lower part of the stomach. It is often associated with chronic infection with Helicobacter pylori bacteria and is more common in Asia than in other parts of the world.
- Proximal stomach cancer is a type of adenocarcinoma in which cancerous cells form in the first (proximal) part of the stomach and may extend into the gastroesophageal junction, where the esophagus (the tube through which food and liquid travel) joins the stomach. Proximal stomach cancer is more common in the United States than in other parts of the world and tends to develop in people who are obese or have gastro-esophageal reflux disease (GERD).
- Diffuse stomach cancer is an aggressive type of adenocarcinoma that grows rapidly within the cells of the stomach wall. Because it does not form a mass or a tumor, this type of stomach cancer can be difficult to diagnose. It tends to develop in people who are younger and have a family history of the disease or a genetic syndrome.
Other, less common types of stomach cancer include:
- Gastrointestinal stromal tumors (GIST), which develop in the muscle or connective tissue of the stomach
- Carcinoid tumors, which begin in the hormone-producing cells in the stomach
- Lymphoma, which begins in the immune-system cells in the stomach
Many people with stomach cancer have no symptoms at all or experience only vague abdominal discomfort. When symptoms do occur, they often mimic those of less serious conditions such as indigestion or a stomach virus. See your doctor if you have any of the following symptoms:
- stomach pain or discomfort
- a bloated feeling after eating
- nausea and vomiting
- unexplained weight loss and loss of appetite
- difficulty swallowing or excessive belching when eating
- persistent ulcer