Noncancerous tumors of the stomach are unlikely to cause symptoms or medical problems. Occasionally, however, some bleed or become cancerous.
About 99 percent of stomach cancers are adenocarcinomas. Other stomach cancers are leiomyosarcomas (cancers of the smooth muscle) and lymphomas.
Stomach cancer is more common in older people. Less than 25 percent of such cancer occurs in people under age 50. Stomach cancer is extremely common in Japan, China, Chile, and Iceland. In the United States, it's more common in poor people, blacks, and people who live in the north. I's the seventh most common cause of death from cancer in the United States, occurring in about 8 of every 100 000 people. For unknown reasons, stomach cancer is becoming less common in the United States.
Causes
Stomach cancer often begins at a site where the stomach lining is inflamed. However, many experts believe that such inflammation is the result of stomach cancer rather thạn the cause of it. Some experts suggest that stomach ulcers can lead to cалсег, but most people with ulcers and stomach cancer probably had an undetected cancer before the ulcers developed. Helicobacter pylori, the bacteriun that plays a role in producing duodenal ulcers, also may play a role in some stomach cancers.
Stomach polyps, uncommon noncancerous round growths that project into the stomach cavity, are thought to be forerunners of cancer and thercfore are removed. Cancer is particularly likely with certain types of polyp, a polyp larger than ? inch, or several polyps. Certain dietary factors are thought to play a role in the development of stomach cancer. These factors include a high intake of salt, a high intake of carbohydrates, a high intake of preservatives called nitrates, und a low intake of green lenfy vegetables and fruit. However, none of these factors have been proved to cause cancer.
Symptoms
In the early stages of stomach cancer, symptons are vague and easily ignored. When symptoms do develop, they may help indicate where in the stomach the cancer is located. For instance, a feeling of fullness or discomfort after a meat may indicate cancer in the lower part of the stomach. Weight loss or weakness usually results from difficulty in eating or from an inability to absorb some vitamins and minerals. Anemia may result from very gradual bleeding that causes
no other symptorns. Uncommonly, a person may vomit large amounts of blood (hematemesis) or pass black tarry stools (melena). When stomach cancer is advanced, a doctor may be able to feel a mass through the abdominal wall.
Even in the early stages, a small stomach tumor may spread (metastasize) to distant sites. The spread of the tumor may cause liver enlargement, jaundice, fluid accumulation in the abdomen (ascites), and cancerous skin nodules. The spreading cancer also may weaken bone, leading to bone fractures.
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