Sporadic gastric cancer; a complex interaction of genetic and environmental risk factors.

Sporadic gastric cancer usually arises against a background of sequential mucosal changes. H. pylori superficial gastritis progresses to atrophy and intestinal metaplasia and then to dysplasia and cancer. A variety of environmental and host genetic factors influence this process and act at different stages in the pathway. Many different combinations of these risk factors may lead to cancer. Interactions also occur between environmental and genetic factors to increase or decrease their ability to influence the precancerous process. Sporadic gastric cancer is thus the consequence of complex combinations and interactions between many environmental and genetic factors.