Stomach cancer,
also called gastric
cancer, is a cancer that starts in the stomach.
After food is chewed and swallowed, it enters the esophagus, a
tube that carries food through the neck and chest to the stomach. The
esophagus joins the stomach just beneath the diaphragm (the breathing
muscle under the lungs). The stomach is a sac-like organ that holds
food and starts to digest it by secreting gastric juice. The
food and gastric juice are mixed and then emptied into the first part
of the small intestine called the duodenum.
Some people use the word stomach
to
refer to the area of the body between the chest and
the pelvic area. The medical term for this area is the abdomen.
For instance, some people with pain in this area would say they have a
"stomach ache," when in fact the pain could be coming from the
appendix, small intestine, colon (large intestine), or other organs in
the area. Doctors would refer to this symptom as abdominal pain.
This is important because the stomach is only one of many organs in the
abdomen in which cancers may start. Stomach cancer should not be
confused with cancers of
the colon (large intestine), liver, pancreas, or small intestine
because these cancers may have different symptoms, a different outlook,
and different treatments.
The stomach has 5 sections. The upper portion (closest to the
esophagus) is called the cardia.
Next to this is the fundus.
Some cells in these areas of the stomach make acid and pepsin (a
digestive enzyme), the parts of the gastric juice that help digest
food. The lower portion (closest to the intestine) includes the antrum, where the
food is mixed with gastric juice, and the pylorus, which acts
as a valve to control emptying of the stomach contents into the small
intestine. The area between the proximal and distal stomach is the body (corpus) of
the stomach. The upper parts of the stomach (cardia, fundus, and body)
are sometimes called the proximal
stomach, and the lower two (antrum and pyloris) are called
distal stomach.
Cancers starting in different sections of the stomach may cause
different symptoms and tend to have different outcomes. The location
can also affect treatment options.
The stomach has 2 curves, which form its upper and lower borders. They
are called the lesser
curve and greater
curve, respectively. Other organs next to the stomach
include the colon, liver, spleen, small intestine, and pancreas.
The stomach has 5 layers. It is important to know about these layers
because as a cancer grows deeper into them, the prognosis (outlook for
survival) is not as good. The innermost layer is the mucosa. This is
where stomach acid and digestive enzymes are made, and where most
stomach cancers start. Under this is a supporting layer called the submucosa. This is
surrounded by the muscularis,
a layer of muscle that moves and mixes the stomach contents. The next 2
layers, the subserosa
and the outermost serosa,
act as wrapping layers for the stomach.
Stomach cancers tend to develop slowly over many years. Before a true
cancer develops, pre-cancerous changes often occur in the lining of the
stomach. These early changes rarely cause symptoms and therefore often
go undetected.
Stomach cancers can spread, or metastasize,
in different ways. They can grow through the wall of the stomach and
invade nearby organs. They can also spread to the lymph vessels and
lymph nodes. Lymph nodes are bean-sized structures near many body
structures that help fight infections. The stomach has a very rich
network of lymph vessels and nodes. If cancer spreads to the lymph
nodes, the outlook for survival is not as good. When the stomach cancer
becomes more advanced, it can travel through the bloodstream and spread
to organs such as the liver, lungs, and bones.
Types of Cancers in the Stomach
Adenocarcinoma: About 90% to 95% of cancerous (malignant) tumors of the
stomach are adenocarcinomas. The term stomach cancer, or gastric
cancer, almost always refers to adenocarcinoma. This cancer develops
from the cells that form the innermost lining of the stomach's mucosa.
The following other, less common tumors are also found in the stomach:
Lymphoma: These are cancers of the immune system tissue that are
sometimes found in the wall of the stomach. They account for about 4%
of stomach cancers. Prognosis and treatment depend on whether the
lymphoma is aggressive or is a slow-growing MALT lymphoma. For further
information, see the American Cancer Society document, Non-Hodgkin
Lymphoma.
Gastrointestinal stromal tumor (GIST): These are rare tumors that seem
to start in cells in the wall of the stomach called interstitial cells
of Cajal. Some are non-cancerous (benign); others are cancerous.
Although these tumors can be found anywhere in the digestive tract,
most (70%) occur in the stomach. For more information, see the American
Cancer Society document, Gastrointestinal Stromal Tumor (GIST).
Carcinoid tumor: These are tumors that start in hormone-making cells of
the stomach. Most of these do not spread to other organs. About 3% of
stomach cancers are carcinoid tumors. For more information, see the
American Cancer Society document, Gastrointestinal Carcinoid Tumors. The
information in the remainder of this document refers only to
adenocarcinoma of the stomach.
Revised: 04/23/2007
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