Cardiac Metaplasia: Follow, Treat, or Ignore?

Over the past two decades, evidence has accumulated to challenge the traditional view that cardiac mucosa, which is comprised exclusively of mucus glands, is the normal lining of the most proximal portion of the stomach (the gastric cardia). There is now considerable evidence to suggest that cardiac mucosa develops as a GERD-induced, squamous-to-columnar esophageal metaplasia in some, if not all, cases. Although cardiac mucosa lacks the goblet cells commonly required for a histologic diagnosis of intestinal metaplasia, cardiac mucosa has many molecular features of an intestinal-type mucosa, and appears to be the precursor of intestinal metaplasia with goblet cells. In apparently normal individuals, cardiac mucosa is commonly found in a narrow band, less than 3 mm in extent, on the columnar side of the squamo-columnar junction at the end of the esophagus. A greater extent of cardiac mucosa can be found in GERD patients, and the magnitude of that extent appears to be an index of GERD severity. Presently, the risk of adenocarcinoma imposed by cardiac mucosa is not clear, but appears to be far less than that of intestinal metaplasis with goblet cells. The British Society of Gastroenterology accepts an esophagus lined by cardiac mucosa as a "Barrett's esophagus". However, if one defines Barrett's esophagus as a metaplasia that predisposes to cancer, then only intestinal metaplasia clearly fulfills that criterion at this time. Well-designed, prospective studies are needed to establish the malignant potential of cardiac mucosa.