[Helicobacter pylori and gastric cancer].

Since its discovery and identification in gastric tissue by Marshall and Warren in 1983, our knowledge about the effects of Helicobacter pylori infection has grown considerably. Its role in the multifactorial pathology of peptic ulcer disease (gastrodudodenal ulcer disease), gastric adenocarcinoma, and MALT lymphoma is now widely accepted while its involvement in extraintestinal disease is still controversial.The correlation between the colonization of the stomach by H. pylori and gastric lymphoma has been demonstrated in multiple studies. Between 65 and 80% of distal gastric adenocarcinomas are attributed to H. pylori infection. However, gastric carcinogenesis cannot be explained by H. pylori infection alone. Among those individuals infected by this bacteria, only a small percentage (2-5%) ever develops gastric cancer, the majority exhibit benign lesions. There is a wide individual variation in the outcome of this infection in patients. This individual and population specific variation is due to the intricate relationship between genetics, the environment, bacterial virulence, diet, and socio-economic status and it explains the multiple outcomes of this infection. In this article, we conduct a review of the widely accepted theories regarding gastric cancer, Helicobacter pylori, the correlations and enigmas between them, the reported geographical variations, and the various proposed hypotheses on the carcinogenic mechanism of Helicobacter pylori.