Are all different types of Barrett's epithelium originally present, or do they appear only after some period of evolution?
D. Parekh, G.W.B. Clark, T.R. DeMeester (Los Angeles)
The most severe histological consequence of chronic gastroesophageal reflux is Barrett's esophagus. Barrett's mucosa is a metaplastic columnar epithelium that replaces the normal squamous epithelium in the esophagus. A wide variety of cell types and histological patterns are encountered in Barrett's mucosa. A distinctive specialized columnar epithelium (SCE) is diagnostic of this condition [1,2]. SCE is characterized by columnar cells, goblet cells and a villous like structure. The columnar cells lack absorptive capabilities or ultrastructure characteristics of true intestinal cells making them thus, an example of incomplete intestinal metaplasia . The other two types of histopathological patterns described in Barrett's epithelium include junctional or cardiac type Barrett's mucosa with a predominantly foveolar surface containing mucous glands and resembling gastric cardia type mucosa and fundic type which is the only variety of Barrett's epithelium that contains both parietal and chief cells with atrophic fundic glands [1-3]. The glandular structures of the fundic type epithelium appear sparse and shortened causing it to appear atrophic compared to normal gastric mucosa [1-3].
It is now well established that Barrett's mucosa is a premalignant lesion and relative to the general population the risk of a patient with Barrett's esophagus developing an esophageal cancer is increased 30-50-fold [1,3]. The development of adenocarcinoma in Barrett's esophagus is preceded by areas of underlying dysplasia, thereby providing evidence in support of the dysplasia-carcinoma sequence in this lesion . The specialized columnar epithelium in Barrett's mucosa has a special significance in this condition: when adenocarcinoma of the esophagus develops in Barrett's mucosa, it virtually always arises in a short or long segment of specialized metaplastic columnar epithelium and not from fundic or cardiac type epithelium .
A commonly used definition of Barrett's esophagus has been the presence of columnar epithelium extending more than 3 cm above the normal cardioesophageal junction . This is due to an imprecise relationship between lower esophageal sphincter (LES) and the squamocolumnar junction i.e., there may be a 2-3 cm dis-association between the Z-line and manometrically-defined LES in normal adults. Accurate diagnosis of Barrett's esophagus requires endoscopy with careful documentation of landmarks of the diaphragm (crural impression), gastroesophageal junction and Z-line. In patients with hiatal hernia this is particularly important; otherwise an excess amount of cardiac type Barrett's esophagus may be diagnosed if the biopsies have been obtained from the hiatal hernia. It is because of this difficulty that the prevalence of different types of mucosa in Barrett's esophagus have been controversial.