Stomach cancers are classified according to what sort of tissues they start in.
The most common type arises in the glandular tissue lining the stomach. These tumors are called adenocarcinomas and account for over 95 percent of all stomach tumors.
One particular form of this cell type, unusual in the U.S. but more common in Japan, is the superficial spreading adenocarcinoma that essentially replaces the lining (mucosa) of the stomach with sheets of malignant cells.
Another subtype is scirrhous carcinoma (linitis plastica), a poorly differentiated mixture of mucin-producing carcinoma cells that infiltrates the muscle wall and turns it into rigid, leatherlike scar tissue that cannot stretch or move during the normal digestive process (peristalsis).
The disease can spread directly through the stomach wall into adjacent organs and through the lymph system to nodes in the abdomen, the left side of the neck and the left armpit.
Metastases through the bloodstream can spread to the liver, lungs, bone and brain. Metastases are also found in the lining of the abdominal cavity (peritoneum) and around the rectum.
Those at significantly higher risk are those aged between 50 and 59; workers in various industries (coal mining, nickel refining, rubber and timber processing); workers exposed to asbestos fibers; people with pernicious anemia who are 5 to 10 percent more likely to develop gastric cancer; and persons whose diet contains smoked, highly salted and barbecued foods.
Japanese immigrants have a decreased incidence of this cancer when they adopt an American diet and lifestyle, with a tenfold drop after two generations.
The symptoms of stomach cancer are similar to the symptoms of a hiatal hernia or peptic ulcer, namely a vague pain aggravated by food, nausea, heartburn and indigestion. These symptoms are often thought to be due to the stress of psychosomatic illness and are treated with antacids or H-2 blockers. Unfortunately, the temporary relief this treatment brings often delays the tests that could diagnose cancer.
Loss of appetite, feelings of fullness after even a small meal, and weight loss are common - upper abdominal pain, vomiting after meals and weight loss are seen in 80 to 90 percent of cases.
There also may be mild anemia, weakness, gastrointestinal bleeding and vomiting of blood. Both vomiting blood and rectal bleeding are seen in peptic ulcer disease, esophageal varices (varicose veins in the esophagus that grow and burst, a disease common in drinkers), and occasionally leiomyosarcomas.
Gastric cancers often seem to be benignulcers, which are like pits in the stomach lining. Larger ulcers - more than 3/4 in. (2cm) in diameter - that have borders raised above the level of the surrounding stomach are more likely to be malignant.
Diagnosis may include the following:
- Enlarged lymph nodes above the left collarbone (supraclavicular node)
- Nodal masses around the rectum, inside the navel or in the abdomen (involving the ovary)
- Enlarged liver (hepatomegaly)
- Increased fluid intake in the abdomen (ascites)
Blood and Other Tests might involve:
- Test for hidden blood in the stools
- Complete blood count (CBC), which may indicate anemia from gastrointestinal bleeding
- Serum chemistry profile to evaluate abnormal liver and bone chemistry enzymes, including tests for elevated levels of carcinoembryonic antigen (CEA) and levels of serum ferritin to indicate iron deficiency
- Analysis of gastric acid to detect achlorhydria
Imaging may involve:
- X-rays of the upper gastrointestinal tract (UGI series) by standard and double-contrast methods may find larger ulcer lesions
- Chest X-rays
- CT scan of the abdomen
- Bone scan if the bone enzyme alkaline phosphatase is elevated in the serum
- Ultrasound to help measure tumor size and predict recurrence
Endoscopy and Biopsy may involve examination of the stomach through a gastroscope inserted through the esophagus (fiberoptic endoscopy) to find ulcers and masses. It is the most definitive test for diagnosis of stomach cancer. Seventy percent of early malignant ulcers may look benign and even heal, but are usually positive on biopsy.
In this procedure, the esophagus and stomach are examined using a thin, lighted tube (gastroscope) which is passed through the mouth and esophagus to the stomach. The patient's throat is sprayed with a local anesthetic to reduce discomfort and gagging. Patients may also receive medication to relax them. Through the gastroscope, the doctor can look directly at the inside of the stomach. If an abnormal area is found, the doctor can remove some tissue through the gastroscope.
A small piece of tissue may be removed form any suspicious area for biopsy analysis by a pathologist, or a brush can be passed through the gastroscope to obtain cells in a way similar to a Pap smear. Tissue and brush biopsies can diagnose 98 percent of cases.
Stomach cancer is a somewhat treatable disease, with over half the patients with early stage disease being curable. Early-stage disease accounts for only 10 to 20 percent of all cases diagnosed in the U.S.. In early-stage disease over 50 percent are curable.
Five-year survival for more advanced cancers range from around 20 percent for those with regional disease to almost nil for those with distant metastases. Treatment for metastatic cancer can relieve symptoms and sometimes prolong survival, but long remissions are not common.
The ideal treatment is radical surgery, meaning that most or all of the stomach is removed (subtotal or total gastrectomy), along with the surrounding lymph nodes. Radical surgery is the only treatment that can lead to a cure, though lesser surgical procedures can play a significant role in therapy designed to relieve symptoms.
Radiation and chemotherapy are also treatment options. Neither has been shown to improve the outlook for those with advanced tumors, generally, although some patients with responsive tumors may benefit.