MSH: A condition with damage to the lining of the lower ESOPHAGUS resulting from chronic acid reflux (ESOPHAGITIS, REFLUX). Through the process of metaplasia, the squamous cells are replaced by a columnar epithelium with cells resembling those of the INTESTINE or the salmon-pink mucosa of the STOMACH. Barrett's columnar epithelium is a marker for severe reflux and precursor to ADENOCARCINOMA of the esophagus.,NCI: A condition in which the cells lining the lower part of the esophagus have changed or been replaced with abnormal cells that could lead to cancer of the esophagus. The backing up of stomach contents (reflux) may irritate the esophagus and, over time, cause Barrett's esophagus.,NCI: Esophageal lesion lined with columnar metaplastic epithelium which is flat or villiform. Barrett epithelium is characterized by two different types of cells: goblet cells and columnar cells. The symptomatology of Barrett esophagus is that of gastro-esophageal reflux. It is the precursor of most esophageal adenocarcinomas.