Review article: intestinal metaplasia and gastric carcinogenesis.

Gastric intestinal metaplasia, an intermediate step in Correa's cascade of gastric carcinogenesis, is generally regarded as a pre-malignant lesion. Epidemiological studies suggest that patients with intestinal metaplasia have more than a 10-fold increased risk of developing gastric cancer. Within the subclassification of intestinal metaplasia, incomplete or type III intestinal metaplasia appears to be associated with even higher malignant potential. The topographical distribution of intestinal metaplasia may also have prognostic implications. Certain genetic and epigenetic alterations have been demonstrated in gastric intestinal metaplasia which straddle into gastric cancer. These findings suggest that genetic changes occur early in the multistep gastric carcinogenesis process. Unlike Barrett's oesophagus and colonic polyp, which have well-defined surveillance guidelines, there is no widely accepted surveillance programme for gastric intestinal metaplasia. An annual surveillance programme may allow early detection of gastric cancer, which theoretically may improve survival. It remains elusive whether the treatment of Helicobacter pylori infection may reverse gastric intestinal metaplasia or reduce the subsequent risk of cancer development. Further controlled studies with longer follow-up are needed to resolve this controversy. The role of chemo-prophylactic agents, e.g. cyclo-oxygenase-2 inhibitor, should be investigated.