THE HISTOPATHOLOGY OF TREATED BARRETTS-ESOPHAGUS - SQUAMOUS REEPITHELIALIZATION AFTER ACID SUPPRESSION AND LASER AND PHOTODYNAMIC THERAPY

Columnar metaplasia of the lower esophageal epithelium (Barrett's esop hagus) occurs in response to acid reflux, and its most important long- term complication is malignancy. In view of this, techniques are being explored for the eradication of Barrett's esophagus, and histopatholo gists will increasingly be required to assess response to these therap ies in esophageal biopsy samples. The histopathologic features before and after treatment were studied in biopsy samples from 16 patients re ceiving omeprazole only, 10 treated by KTP laser photoablation, and fi ve who underwent photodynamic therapy. All the treatment modalities re sulted in histologic changes with at least partial squamous reepitheli alization of the metaplastic columnar epithelium. The histologic findi ngs suggest three main mechanisms for this: encroachment of adjacent s quamous epithelium at the squamocolumnar junction, extension of epithe lium from the submucosal gland duct to form squamous islands, and squa mous metaplasia within the Barrett's columnar mucosa itself. The latte r mechanism implies the existence of pluripotential stem cells within Barrett's mucosa. A relatively common finding was residual glandular m ucosa, nonneoplastic and dysplastic, beneath squamous epithelium indic ating the requirement for histologic confirmation of endoscopically su spected complete squamous reepithelialization with sufficiently deep b iopsies.