Abstracts
2000 Digestive Disease Week

# 2252 Ultrastructural Characteristics of Regenerating Squamous Islands in Barrett’s Epithelium.
Majid Hashemi, Cedric G. Bremner, L. Koss Kelly, Ross M. Bremner, Reginald V. Lord, Para Chandrasoma, Jorg Theisen, Otavio L. Gastal, Jeffrey H. Peters, Tom R. Demeester, Los Angeles, CA

Background: Islands of squamous epithelium are often seen after antireflux treatment. They may represent the early stages of regression of Barrett‘s columnar epithelium to squamous epithelium. We describe the ultrastructural features of cells in these squamous islands and compare these with cells from normal squamous epithelium. Methods: 38 biopsy specimens were obtained from seven patients with endoscopically visible islands of squamous epithelium within a segment of Barrett s epithelium after antireflux surgery. Biopsies from squamous epithelium from grossly normal esophagus in the same patient were used for comparison. Light microscopy of embedded samples was used for orientation and selection of the area for thin section (700-900 angstroms) transmission electron microscopy (TEM). Results: In none of the specimens of squamous islands was the typical three layered pattern of normal esophageal squamous epithelium identified. Apoptosis of cells with features characteristic of Barrett s epithelium was observed in the region immediately adjacent to immature squamous cells with lower concentration of glycogen granules and poorly developed junctional complexes. The table summarizes some of the features of cells from the squamous islands. Conclusion: The cells of squamous islands share features of normal esophageal squamous epithelium, most closely resembling cells of the prickle layer. Few cells have features of cells seen in the basal layer of the normal esophageal squamous epithelium, and there are no features of polarity seen in cells from squamous islands. These findings may be relevant to the question of the stability and long-term endurance of the regenerated squamous epithelium.