Stomach cancer is also called gastric cancer and starts in the stomach. Once food has been chewed and swallowed it enters the esophagus, a tube that carries food through the neck and chest to the stomach. The esophagus connects to the stomach right beneath your diaphragm, which is a muscle used for breathing underneath your lungs.
Stomach cancer is cancer that occurs in the stomach, the muscular sac located in the upper middle of your abdomen, just below your ribs. The cancer may spread from the stomach to other parts of the body, particularly the liver, lungs, bones, lining of the abdomen and lymph nodes.
The stomach is somewhat like a sack and holds food; it also starts to digest it by secreting gastric juice. Food and gastric juices are mixed in the stomach and then empty into the first part of the small intestine called the duodenum.
Sometimes people use the word, 'stomach,' to mean the entire area of the body between the chest and the pelvis. The medical term for this area of the body is the, 'abdomen.' For example, sometimes people experiencing pain in their abdomen say they have a, 'stomach ache,' when the pain could be coming from their appendix, small intestine, colon , or some other organs in their abdomen. Doctors talk about these kinds of pain as, 'abdominal pain.'
The reason this is important is because the stomach is one of a number of organs in the abdomen, and cancer might start in any of these organs. It is important not to confuse Stomach cancer with colon cancer, for example, or small intestine cancer or liver cancer because these forms of cancer have different symptoms. These forms of cancer also have different outlooks, and different treatments.
Parts of the Stomach
The human stomach has five parts:
The first three parts of the stomach; the Cardia, Fundus, and Body, are referred to as the, 'Proximal Stomach.' The lower two parts; the Antrum and the Pylorus, are referred to as the, 'Distal Stomach.' Cancers that start in different sections of the stomach might cause different symptoms; they also usually have different outcomes. Treatment options can also be affected by the location of the cancer.
There are two curves in the stomach that form the upper and lower borders. These curves are referred to as the, 'Lesser Curve," and, 'Greater Curve.' There are other organs near the stomach; they include the liver, colon, small intestine, spleen and pancreas.
There are five layers in the stomach wall, and it is important to know and understand these layers because as a cancer in the wall of the stomach grows deeper into them the prognosis deteriorates. The innermost layer is the mucosa and this is where stomach acid and digestive enzymes are made as well as where most forms of stomach cancers begin. Under the mucosa is a supporting layer called the submucosa. The submucosa is surrounded by a layer of muscle called the, 'muscularis', which is a layer of muscle that moves and mixes the stomach's contents. The outer-most two layers, called the, 'subserosa,' and the, 'serosa,' perform as wrapping layers for the stomach.
The Development of Stomach Cancer
Stomach cancers usually develop slowly, and over a period of many years. Pre-cancerous changes often occur in the lining of the stomach before a true cancer develops. Many times the early changes do not cause any symptoms and go undetected.
There are different ways that stomach cancers can spread. One way they can grow is through the wall of the stomach, and then continue on to invade nearby organs. They may also spread to lymph vessels and nearby lymph nodes, which are bean-sized structures located near many body structures that help fight infections. One of the features of the stomach is a very extensive network of lymph vessels and nodes. The outlook for survival decreases significantly if cancer spreads to the lymph nodes. As stomach cancer advances, it has the potential to travel through the blood stream and spread, or, "metastasize,' to organs such as the lungs, liver and bones.
Different Types of Stomach Cancer
Adenocarcinoma
Approximately 90% to 95% of cancerous tumors of the stomach are Adenocarcinomas. The term, 'stomach cancer,' nearly always refers to Adenocarcinoma. This form of cancer develops from the cells that form in the innermost lining of the stomach, or, 'Mucosa.'
There are also some other, less common tumors that may be found in the stomach, such as:
Lymphoma
Lymphomas are cancers of the immune system tissue and are sometimes found in the wall of the stomach, accounting for about 4% of all stomach cancers. The prognosis and treatment of a Lymphoma depends on whether it is aggressive or is a slow-growing lymphoma.
Gastrointestinal Stromal Tumor
Gastrointestinal Stromal Tumors are rare and seem to start in cells in the wall of the stomach called, 'interstitial cells of Cajal.' Some of these tumors are non-cancerous, or benign; others are cancerous. About 60% to 70% of these tumors occur in the stomach, but they can be found anywhere in the digestive tract.
Carcinoid Tumor
Carcinoid Tumors start in hormone-making cells in the stomach and most of them do not spread to other organs. Approximately 3% of all stomach cancers are carcinoid tumors.
Early symptoms may include:
Later signs and symptoms may include:
The American Cancer Society's estimates for stomach cancer in the United States for 2015 are:
