Different patterns of cytokeratin expression in Barrett's esophagus--what is beyond?

Barrett's esophagus (BE) was recently defined by the presence of metaplastic intestinal mucosa (specialized columnar epithelium) in the distal esophagus. However, different epithelial types that were classified by histological criteria occur at the gastro-esophageal region. The purpose of this study was to evaluate the expression of different subtypes of cytokeratins in Barrett's mucosa (BM) and to contribute to the discussion about the significance of cytokeratin expression patterns within the gastro-esophageal junction. Immunohistochemical detection of a wide spectrum of cytokeratins (CK7, CK10, CK19, CK20, CKHW, CK116 and CKAE1/AE3) was performed in bioptic samples obtained from 10 adults with BE and in nine samples of gastric mucosa from the same patients. Cytokeratin immunoreactivity of epithelial cells appearing in BM was particularly dependent on the differentiation degree of these cells. Less differentiated cells were positive for CK7 and CK10, as were the cells of the necks of gastric mucosa and the ducts of esophageal glands. In contrast, differentiated goblet cells showed only weak or negative immunoreactivity for CK7 and CK10. CK20 was positive predominantly in superficial parts of BM. Immunostaining with antibodies detecting a wider spectrum of cytokeratins (CK116, CKAE1/AE3) revealed prominent irregularities, particularly regarding the intensity of immunoreaction. BM showed only weakly positive staining for high molecular weight keratins. Our findings suggest that the mode of CK expression in BM is closely related to the differentiation degree of cells forming BM, and that the cytokeratin inmmunoreactivity pattern in BM is similar to that in the cells forming the necks of gastric glands and ducts of esophageal glands. However, it differs from squamous epithelium of esophageal mucosa.