Nonepithelial Tumors

Leiomyoma

Schwannoma

Granular cell tumor

Leiomyosarcoma

Gastrointestinal stromal tumor (GIST) (gradation from benign to malignant)

Kaposi sarcoma

Others

Malignant Lymphoma

* The Laurén classification subdivides adenocarcinomas into intestinal and diffuse types.

pathway by which intestinal-type gastric cancers develop. Adenomas containing mucosal dysplasia can also become malignant.

Environment.

Environmental influences may be critical in gastric carcinogenesis. [35] When families migrate from high-risk to low-risk areas (or the reverse), successive generations acquire the level of

risk that prevails in the new locales. The diet

TABLE 17-5-- Factors Associated with Increased Incidence of Gastric Carcinoma

Environmental Factors

Infection by H. pylori

• Present in most cases of intestinal-type carcinoma

Diet

• Nitrites derived from nitrates (water, preserved food)

• Smoked and salted foods, pickled vegetables, chili peppers

• Lack of fresh fruit and vegetables

Low socioeconomic status

Cigarette smoking

Host Factors

Chronic gastritis

• Hypochlorhydria: favors colonization with H. pylori

• Intestinal metaplasia is a precursor lesion

Partial gastrectomy

• Favors reflux of bilious, alkaline intestinal fluid

Gastric adenomas

• 40% harbor cancer at time of diagnosis

• 30% have adjacent cancer at time of diagnosis

Barrett esophagus

• Increased risk of gastroesophageal junction tumors

Genetic Factors

Slightly increased risk with blood group A

Family history of gastric cancer

Hereditary nonpolyposis colon cancer syndrome

Familial gastric carcinoma syndrome (E-cadherin mutation)

is suspected to be a primary factor, and adherence to certain culinary practices is associated with a high risk of gastric carcinoma. Lack of refrigeration; consumption of preserved, smoked,

cured, and salted foods; water contamination with nitrates; and lack of fresh fruit and vegetables are common themes in high-risk areas. The consumption of dietary carcinogens, such as Nnitroso

compounds and benzopyrene, appears to be particularly important. Conversely, intake of green, leafy vegetables and citrus fruits, which contain antioxidants such as ascorbate

(vitamin C), alpha-tocopherol (vitamin E), and beta-carotene, is negatively correlated with gastric cancer. A specific protective role for any one of these nutrients cannot be assumed,

however, since intake of fresh food may simply displace consumption of preserved foods.

So far there is no conclusive evidence linking alcohol intake and cigarette smoking to the development of gastric cancer. Despite initial concern, to date there appears to be no increased

risk of stomach cancer from the use of antacid drug therapies.

Host.

Autoimmune gastritis, like H. pylori infection, increases the risk of gastric cancer, presumably due to chronic inflammation and intestinal metaplasia. It has been noted that blood group A

patients have higher risk but it is not yet clear whether this is related to the binding of H. pylori to Lewis B antigen, or to other mechanisms.

Within the United States, blacks, Native Americans, and Hawaiians have a higher risk of developing gastric cancer. But since only about 8% to 10% of patients with gastric cancer have a

family history of this disease, genetic factors are unlikely to be a major influence. Environmental factors mentioned above, are likely to play a major role in the higher incidence of gastric

cancer among these various groups. Genetic traits play a critical role in some familial cases of gastric cancer, including gastric carcinoma occurring in the hereditary nonpolyposis

colorectal cancer (HNPCC) syndrome. Recently, E-cadherin gene (CDH1) germ-line mutations have also been identified as the underlying genetic basis for another familial gastric cancer

syndrome that is characterized by early occurrence of diffuse type adenocarcinoma.[36] These patients are also at risk for developing lobular breast cancer.[37]

Date: 2016-04-22; view: 705