The stomach wall has three linings (inner, middle, and outer). Cancer of the stomach, also called gastric cancer, is a disease in which malignant (cancer) cells grow from the inner lining of the stomach. Stomach cancer can develop in any part of the stomach and then may spread throughout the stomach and to other organs. Stomach cancers are classified according to the type of tissue from which they originate. The most common type of stomach cancer is adenocarcinoma, which starts in the glandular tissue of the stomach, and accounts for 95% of all stomach cancers. Other forms of stomach cancer include lymphomas, which involve the lymphatic system, and sarcomas, which involve the connective tissue (such as muscle, fat, or blood vessels). The exact cause of stomach cancer is unknown, but various medical conditions can increase the risk, including: 

• gastritis (stomach inflammation) 
• pernicious anemia 
• gastric polyps
• gastric (peptic) ulcer

In addition, Helicobacter pylori ( H. pylori ) infection of the stomach increases the risk of developing stomach cancer. H. pylori is a bacteria that infects the lining of the stomach and causes chronic inflammation and ulcers. 
Stomach cancer is found most often in people who are over age 55, and affects men more often than women. The risk is greater if an immediate family member has had stomach cancer. 
Stomach cancer can often be cured if it is found and treated at an early stage. Unfortunately, the outlook is poor if the cancer is already at an advanced stage. 
  In the early stages of stomach cancer, a patient may have a few vague symptoms (indigestion, nausea, feeling bloated, poor appetite). These symptoms are similar to those caused by a hiatal hernia or peptic ulcer and may be treated with antacids or histamine blockers for temporary relief. As a result, patients may not recognize these as serious symptoms and may not go to the doctor for a long time. A gastric tumor can grow very large before it causes other symptoms. 
In later stages of stomach cancer, a patient may have the following symptoms: 

• Discomfort in the upper or middle part of the abdomen 
• Blood in the stool (which appears as black, tarry stools) 
• Vomiting or vomiting blood 
• Weight loss 
• Pain or bloating in the stomach after eating 
• Weakness or fatigue associated with mild anemia 

The physician may find some abnormalities during a physical exam, including enlarged lymph nodes, enlarged liver, and increased fluid in the abdomen (ascites). However, these findings generally indicate advanced stomach cancer. 
When a patient has some of the initial vague symptoms, such as indigestion, weight loss, nausea, and loss of appetite, the doctor may order screening tests. These tests include: 

• Blood tests, including blood chemistry (which looks for disease-causing substances in the blood) and complete blood count (to determine the number of red blood cells) 
• Upper GI series. These are X-rays of the esophagus and stomach (the upper gastrointestinal, or GI tract), taken after the patient drinks a barium solution. The barium outlines the stomach on the X-ray, helping the doctor find tumors or other abnormal areas. 
• Fecal occult blood test to look for blood in the stool 
• Gastroscopy and biopsy. This test examines the esophagus and stomach using a thin, lighted instrument called a gastroscope, which is passed through the mouth down to the stomach. Through the gastroscope, the doctor can look directly at the inside of the stomach. If an abnormal area is found, the doctor will remove some tissue for examination (biopsy). A biopsy is the only sure way to diagnose cancer. Gastroscopy and biopsy are the best methods of identifying stomach cancer. 
• CT scan, a special type of x-ray that takes detailed images of the organs 

One of the biggest concerns about a cancer diagnosis is whether the cancer has spread (metastasized) beyond its original location. To determine this, the doctor assigns a number (I through IV) to the diagnosis. The higher the number, the more the cancer has spread throughout the body. This is called "staging." 
  Stage I: The cancer has spread all the way through the inner lining of the stomach wall into the middle layer, or to nearby lymph nodes. 
Stage II: The cancer has spread to the other layers of the stomach wall or to nearby lymph nodes. 
Stage III: The cancer has spread all the way through the stomach wall, into nearby lymph nodes, or into nearby organs. 
Stage IV: The cancer has metastasized to other sites in the body. 
  Stomach cancer may be treated with the following, alone or in combination: 
Surgery, called gastrectomy, to remove all of the stomach (total gastrectomy) or part of the stomach, as well as some of the tissue surrounding the stomach. The doctor will also take biopsies of lymph nodes near the stomach to check for cancer cells. Lymphoma of the stomach is more frequently treated by gastrectomy than is adenocarcinoma. Only about one-third of stomach cancer cases can be treated and cured with surgery. 
Chemotherapy (drugs that kill or slow the growth of rapidly multiplying cancer cells) 
Radiation therapy (high levels of radiation to kill cancer cells or prevent them from multiplying, while minimizing damage to healthy cells) Cancer of the stomach is difficult to cure unless it is found at an early stage (before it has spread). Unfortunately, because early stomach cancer has few symptoms, the disease is usually advanced when the diagnosis is made. However, advanced stomach cancer can still be treated and the symptoms can be relieved. 
  Treatment of stomach cancer depends on the stage of the cancer: 
Stage I: Gastrectomy, sometimes followed by chemoradiation (combination of chemotherapy and radiation therapy) 
Stage II: Gastrectomy, sometimes followed by chemoradiation. The patient may also receive chemotherapy before and after surgery 
Stage III: Total gastrectomy. The patient may receive chemoradiation after surgery, or chemotherapy before and after surgery 
Stage IV: Total gastrectomy; chemoradiation; chemotherapy, radiation, or surgery to relieve pain and symptoms