Gastric cancer, also called stomach cancer, is a malignant tumor within the stomach. About 85 to 95 percent of gastric cancer cases are a type of cancer called adenocarcinoma—which develops in cells lining glandular types of internal organs, such as the lungs, breasts, colon, prostate, pancreas, cervix and stomach—that form in the mucosa, the lining of the stomach.
About 40 percent of stomach cancers develop in the lower part of the stomach; another 40 percent form in the middle part; and 15 percent develop in the upper part. In about 10 percent of cases, the cancer develops in more than one part of the organ.
Stomach cancer can spread to the esophagus or small intestine, as well as lungs, ovaries and bones. These cancers can also extend through the stomach wall to adjacent lymph nodes and organs. Unless it is caught early, gastric cancer is very difficult to cure—and unfortunately, because early stomach cancer causes few symptoms, it is usually in an advanced stage for being diagnosed. While it may not be possible to cure advanced-stage gastric cancer, it can be treated and symptoms can be ameliorated.
Worldwide, about 760,000 cases of gastric cancer are diagnosed a year, more than 24,000 of which occur in the United States. This cancer occurs more in men than women, and is more common in African Americans than Caucasians and older rather than younger individuals.
The types of stomach cancer include:
- Adenocarcinoma: This type of tumor, which starts in the glandular cells of the stomach lining, accounts for up to 95 percent of all stomach cancers.
- Lymphoma: This is a cancer of the immune system tissue in the stomach walls; these tumors grow very quickly.
- Carcinoid tumor: This slow-growing tissue originates in the stomach’s hormone-producing cells. These tumors tend to metastasize less often than adenocarcinomas.
- Gastrointestinal stromal tumor: This is a rare type of tumor that forms from the interstitial cells of Cajal, which are part of the autonomic nervous system and trigger gut contraction. Only about 5,000 gastrointestinal stromal tumors are diagnosed in the U.S. each year, and while these cancers can form anywhere from the esophagus to rectum, about 60 to 70 percent form in the stomach.