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1083) Helicobacter pylori infection is a major etiologic factor of gastric carcinoma, especially the intestinal type of adenocarcinoma. However, most individuals infected with H. pylori do not develop cancer because:

Only certain types of H. pylori are carcinogenic and need environmental and host factors to result in carcinoma The development of carcinoma takes several decades, and most individuals acquire the infection only in late adulthood The carcinogenic effect of H. pylori is restricted to patients with preexisting gastric pathologies Dietary factors are more important than H. pylori infection Most cases of H. pylori gastritis are treated in the early stages

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• Epidemiologic studies have shown a sixfold increased risk of gastric carcinoma in individuals infected with H. pylori. Infection and gastric cancer risk are high in Japan and Colombia. However, in Africa, where the infection rate is also high, the gastric cancer rate is very low. This so-called African enigma remains unexplained.

• More than half of the world’s population is infected with H. pylori, yet only a very few infected individuals develop gastric cancer.

• CagA and VacA genes are being studied as possible oncogenes. CagA-positive H. pylori strains are associated with alterations in the gastric epithelial cell cycle and apoptosis, more severe mononuclear and neutrophilic infiltrates, and more severe glandular atrophy and intestinal metaplasia. VacA-positive strains are frequently isolated from distal gastric cancers.

• Host factors include certain interleukin-1β subtypes, tumor necrosis factor-α expression, and genetic polymorphisms of mucin (MUC-1) and human leukocyte antigens (HLA).

• Known environmental risk factors are excessive dietary salt and inadequate intake of fruits and vegetables.

Correa P: Bacterial infections as a cause of cancer. J Natl Cancer Inst 2003;95(7):E3.

Selgrad M, Bornschein J, Rokkas T, et al: Clinical aspects of gastric cancer and Helicobacter pylori—screening, prevention, and treatment. Helicobacter 2010;15(Suppl 1):40-45.

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Anatomic Pathology: Infectious Disease Pathology

1083) Helicobacter pylori infection is a major etiologic factor of gastric carcinoma, especially the intestinal type of adenocarcinoma. However, most individuals infected with H. pylori do not develop cancer because:

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