Scanning electron microscopy of the human esophagus: application to Barrett's esophagus, a precancerous lesion.

In Barrett's esophagus, metaplastic columnar epithelium replaces the normal squamous epithelium. The importance of this lesion lies in the increased incidence of adenocarcinoma of the esophagus occurring in patients with Barrett's esophagus. We characterized the surface epithelial cells of Barrett's esophagus using quantitative scanning electron microscopy. Three distinct surface cell types, in addition to the globlet cell, were recognized in Barrett's epithelium: the gastric-like cell and the intestinal-like cell, both of which were similar to normal gastric and small intestinal surface cells, respectively, by quantitative scanning electron microscopy, and the variant cell which had a range of surface features. In four biopsy specimens from the squamo-Barrett's junction in three patients, we found the distinctive cell that had features intermediate between those of squamous and columnar epithelium. On the distinctive cell's surface there are two disparate structures not normally present on the same cell in the gastrointestinal tract: microvilli (a scanning electron microscopy feature of glandular epithelium) and intercellular ridges (a scanning electron microscopy feature of squamous epithelium). The surface characteristics of this cell were almost identical to those of cells found in the transformation zone of the uterine cervix, an area in which squamous epithelium physiologically replaces columnar epithelium. Scanning electron microscopy of Barrett's esophagus has increased our understanding of this precancerous lesion by showing striking cellular heterogeneity. It has also identified the distinctive cell which may represent an intermediate step in the development of Barrett's epithelium during which the surface characteristics of two different cell types, columnar and squamous, coexist in the same cell.