What is Stomach Cancer ?

Stomach cancer is a cancer that starts in the stomach. The medical name for stomach cancer is gastric cancer.
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 sack-like organ that holds food and begins the digestive process by secreting gastric juice. The food and gastric juice are mixed into a thick fluid called chyme, which is then emptied into the first part of the small intestine called the duodenum.
                                                    


In nonmedical conversation, 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 gallbladder may say they have a "stomachache." The medical term for this area is abdomen. And, doctors would refer to this symptom as "abdominal pain."

This point is also very important in considering 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, small intestine, or gallbladder, because these cancers may have different symptoms, a different prognosis (the outlook for chances of survival), and different treatments.

The stomach is divided into five sections. The upper portion (closest to the esophagus) of the stomach is the proximal stomach. Some cells of this area 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 stomach has two curves, which form its upper and lower borders. They are called the lesser and greater curves, respectively. Other organs next to the stomach include the colon, liver, spleen, small intestine, and pancreas.

The stomach is made of 5 layers. Starting from the inside and working our way 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 two layers, the subserosa and the outermost serosa act as wrapping layers for the stomach. It is important to know about these layers because as the cancer grows deeper into them, the prognosis (outlook for cure) gets worse.

Cancer can develop in any of the five sections of the stomach, although most start in the mucosa. Cancers beginning in these 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 precancerous changes that occur in the lining of the stomach. These early changes rarely produce symptoms and therefore often go undetected.

Stomach cancers can spread by several different means. They can grow through the wall of the stomach and eventually grow into nearby organs. They also spread to the lymph system to form distant colonies of cancer in lymph nodes called metastases. Lymph nodes are bean size structures located near many body structures to fight infections. If cancer spreads to 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 (metastases) in organs such as the liver, lungs, and bones (even though it has spread to other organs, it is still called stomach cancer). When this happens, the stomach cancer can't be cured.

Approximately 90% to 95% of the malignant (cancerous) tumors of the stomach are adenocarcinomas. The terms stomach cancer or gastric cancer almost always refer to adenocarcinoma 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 an indolent (slow-growing) lymphoma of mucosa-associated lymphoid tissue (MALT).

Gastric stromal tumors: These tumors develop from the muscle or connective tissue of the stomach wall. Some are benign; others are malignant (cancerous). The malignant stomach tumors are also called gastric sarcomas and make up about 2% of stomach cancers.

Carcinoid tumors: These are tumors of hormone-producing cells of the stomach. Most of these do not spread to other organs. Carcinoid tumors account for about 3% of stomach cancers.

The treatment and outlook of these rarer types of cancers are different from that of adenocarcinoma and are not covered here. Gastrointestinal carcinoid tumors are discussed in a separate document called Gastrointestinal (Digestive System) Carcinoid Tumors.

Prevention
Even though we do not know the exact cause of stomach cancer, it is still possible to prevent many stomach cancers.

The dramatic decline of stomach cancer over the past 60 years is thought to be a result of people reducing many of the known dietary risk factors. This includes greater use of refrigeration for food storage rather than preservation of foods by salting, pickling, and smoking. To reduce the risk, people should avoid diets that are high in smoked and pickled foods and salted meats and fish.

A diet high in fresh fruits and vegetables can also lower stomach cancer risk. The American Cancer Society recommends that people choose most of the foods they eat from plant sources. This includes fruits, vegetables, breads, cereals, pasta, rice, and beans.

Tobacco and alcohol use can increase the risk of cancers of the proximal stomach (the upper portion of the stomach closest to the esophagus). These cancers tend to be particularly hard to treat successfully. The American Cancer Society recommends limiting the use of alcoholic beverages, if you drink at all. Tobacco use increases the risk for many types of cancer and is responsible for about one-third of all cancer deaths in the United States. If you don't use tobacco, don't start. If you already do, call your health care provider or the American Cancer Society for advice about quitting.

It is not yet known if people without symptoms whose stomach linings are chronically infected with the bacteria Helicobacter pylori should be treated. This issue is a topic of current research.
Although avoiding risk factors whenever possible can lower a person's stomach cancer risk, it cannot guarantee protection from this disease. Particularly in countries where stomach cancer is common, early detection may be the best way to improve the chance of successful treatment and reduce the number of deaths caused by the disease.


Diagnostic
Unfortunately, early stage stomach cancer rarely causes symptoms. This is one of the reasons why stomach cancer is so difficult to detect early. The signs and symptoms of stomach cancer include:

Unintended weight loss and lack of appetite
Abdominal pain
Vague discomfort in the abdomen, usually above the umbilicus (navel)
A sense of fullness in the upper abdomen, just below the chest bone after eating a small meal.
Doctors call this early satiety.
Heartburn, indigestion, or ulcer-type symptoms
Nausea
Vomiting, with or without blood
Swelling of the abdomen due to accumulation of fluid and cancer cells. Doctors call this malignant ascites.

Some of these symptoms can occur with noncancerous conditions such as a stomach virus or with other types of cancer. However, people who have any of these problems that persist for a long time should check with their doctor, especially if they are over age 50 or have stomach cancer risk factors.

Since symptoms of stomach cancer often do not appear until the disease is advanced, only about 10% to 20% of stomach cancers in the United States are found in the early stages, before they have spread to other areas of the body.

History and Physical Examination
A complete medical history is an interview in which the doctor asks you questions about risk factors and symptoms that might suggest stomach cancer. The doctor will also want to know about your general health in case you need surgery.

A physical examination provides information about signs of stomach cancer and other health problems. In particular, the doctor will feel your abdomen to see if there is a large tumor. The doctor will also feel to see if your liver is enlarged, whichmight mean the cancer has spread there. The doctor will also use the physical examination to evaluate your general health.

Tests for Stomach Cancer
In the United States, three procedures are commonly used when people have certain risk factors for gastric cancer or when signs and symptoms of this disease are present.

Upper endoscopy: While you are sedated, a doctor puts a thin, flexible, lighted tube called an endoscope down your throat. This instrument allows the doctor to view the lining of your esophagus, stomach, and first part of the small intestine. If abnormalities are noted, biopsies (tissue samples) can be taken. Small (less than 1/8 inch) tissue samples can be removed using instruments operated through the endoscope. The tissue samples are examined under a microscope to see if cancer is present and, if so, what type of cancer. Because you are sedated, this test is not uncomfortable.

When viewed through an endoscope, stomach cancer can appear as an ulcer, a polypoid (mushroom-shaped) or protruding mass, or as a flat, thickened area of mucosa, known as linitis plastica. Linitis plastica is more difficult to recognize in its earliest stages, and only a biopsy of a suspicious area will produce an accurate diagnosis.

Barium upper GI radiographs: For this test, people drink a barium-containing solution that coats the lining of the esophagus, stomach, and first portion of the small intestine. The radiologist then takes multiple x-ray pictures. Because x-rays can't pass through the coating of barium, this will outline any abnormalities of the lining of these organs. To identify early gastric cancers, a "double contrast" technique is commonly used. The patient swallows a thin tube and air is pumped into the stomach after the barium solution. This makes the barium coating very thin so even small abnormalities will show up.

Endoscopic ultrasound: This is a new technique in which a special instrument is used in patients undergoing upper endoscopy. For this test, the endoscope has a small ultrasound probe on the end. This probe releases high frequency sound waves and then detects the sound wave echoes that bounce off tissues of the stomach wall. A computer then translates the pattern of echoes into an image of the stomach wall. This test is usually only available at specialized centers. It is used to estimate how far cancer has spread into the wall of the stomach, into nearby tissues, and to nearby lymph nodes.

Computed tomography (CT) scan: This test uses a special x-ray machine that rotates around the body, taking pictures from many angles. These pictures are combined by a computer to produce detailed cross-sectional images. These help determine if and where stomach cancer has spread outside the stomach. Most often it is used to look for cancer that has spread to the liver.

Magnetic resonance imaging (MRI): Like computed tomography, MRI displays a cross-section of the body. However, MRI uses powerful magnetic fields instead of radiation. The procedure can present cross-sectional views from several angles. These images can also show if the cancer has spread beyond the stomach.

Chest x-ray: This can tell if the cancer has spread to the lungs. It may also be useful to determine if there are any serious lung or heart diseases.

Laboratory studies: These may include a blood test called a complete blood count (CBC) to look for anemia and a fecal occult blood test, which looks for blood in stool (feces). There will also be routine tests of your liver function.

The doctor may recommend other tests and procedures as well.


Treatment
No matter what stage of stomach cancer you have, treatment is available. The choice of treatment you receive depends on many factors. The location and the stage (extent of spread) of the tumor are very important, of course. But in creating your treatment plan, you and your cancer care team will also take your age, general state of health, and personal preferences into account.

The three main treatments for stomach cancer are surgery, chemotherapy, and radiation therapy.
Often the best approach involves using two or more of these treatment methods. Your recovery is one goal of your cancer care team. If a cure is not possible, treatment is aimed at relieving symptoms, such as trouble eating, pain or bleeding. It is important that you understand the goal of your treatment, whether to cure or to palliate (relieve symptoms), prior to starting treatment.


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