Stomach cancer, which is also called gastric cancer, is a cancer that starts in the stomach.
After food is chewed and swallowed, it enters the esophagus, a tube-shaped organ that carries food through the neck and chest. 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 begins the digestive process 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.
The word stomach is often used to refer to the area of the body between the chest and the pelvic area. For instance, some patients with diseases of the appendix, small intestine, colon (large intestine), or stomach may say they have a "stomach ache." The medical term for this area is the abdomen. And doctors would refer to this symptom as abdominal pain.
This point is important in considering gastrointestinal cancers. The stomach is only one of many organs in the abdomen in which cancers may develop. It is important not to confuse stomach cancer with cancers of the colon (large intestine), liver, pancreas, or small intestine because these cancers may have different symptoms, a different prognosis (outlook for chances of survival), and different treatments.
The stomach is divided into 5 sections. The upper portion (closest to the esophagus) of the stomach is called the cardia or proximal stomach. Next to this is the fundus. Some cells of these areas of the stomach produce acid and pepsin (a digestive enzyme), the ingredients of the gastric juice that help digest food. The lower portion (closest to the intestine) is the distal stomach. This area 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 of the stomach.
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 cure) gets worse. Starting from the inside and working out, the innermost layer is the mucosa. This is where stomach acid and digestive enzymes are made. Next 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.
Most stomach cancers start in the mucosa. Cancers beginning in different sections may produce different symptoms and tend to have different outcomes. The location can also affect some of the treatment options that are available.
Stomach cancers are believed to develop slowly over many years. Before a true cancer develops, there are usually pre-cancerous changes that occur in the lining of the stomach. These early changes rarely produce symptoms and therefore often go undetected.
Stomach cancers can spread, or metastasize, in several different ways. They can grow through the wall of the stomach and eventually grow into nearby organs. They can also spread to the lymph system, including lymph vessels and lymph nodes. Lymph nodes are bean-sized structures located near many body structures to fight infections. The stomach has a very rich network of lymph vessels and nodes. If cancer spreads to the lymph nodes, the outlook for cure also gets worse. When the stomach cancer becomes more advanced, it will travel through the bloodstream and form deposits (called metastases) in organs such as the liver, lungs, and bones.
Approximately 90% to 95% of cancerous (malignant) tumors of the stomach are adenocarcinomas. The term stomach cancer, or gastric cancer, almost always refers to adenocarcinoma-type cancer of the stomach. This cancer develops from the epithelial cells that form the innermost lining of the stomach’s mucosa.
The following are other, less common tumors that are 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 cancer is an aggressive lymphoma or a slow-growing (indolent) lymphoma of mucosa-associated lymphoid tissue (MALT).
Gastrointestinal stromal tumors (GIST): These are rare tumors that appear to develop from cells in the wall of the stomach called interstitial cells of Cajal. Some are non-cancerous (benign); others are cancerous (malignant). Although these cancers can be found anywhere in the gastrointestinal tract, the majority (70%) occur in the stomach.
Carcinoid tumors: These are tumors of hormone-producing cells of the stomach. Most of these do not spread to other organs. About 3% of stomach cancers are carcinoid tumors.
By Health Fitness InfoCentre
