Cytokeratin 14, 18, and 19 Expression in Normal Epithelium and in Squamous Cancer of the Esophagus
The normal esophagus is lined by a tough non-keratinizing stratified squamous epithelium, except for a short segment of columnar epithelium at the gastroesophageal junction. Different cell layers have classically been described in this epithelium. The basal or germinative layer is made up of cylindrical, basophilic cells and is covered by several intermediate layers of polyhedral cells. The layers adjacent to the lumen are flattened and form the superficial compartment [1–2]. The proliferative compartment in the squamous epithelium of the esophagus resides in the basal layer of cells. The basal cells can be divided in two topographically different but contiguous compartments both forming the junction with the lamina propria connective tissue: One is a flat layer lying parallel with the longitudinal axis of the esophagus and the second is lining the stromal papillae and lying perpendicular to the luminal axis of the esophagus. The connective tissue of the stromal papillae is highly vascularized . Random mitotic figures can be observed by routine microscopy in both compartments of the basal cell layer. Immunohistochemistry using antibodies directed against BRDU (bromodeoxyuridine), a compound which is incorporated in the nucleus, can demonstrate the presence of S-phase cells in the same layer. For the normal proliferative layer, the labelling index, indicating the ratio between the number of cells showing a positive staining for BRDU and the sum of the labelled and the unlabelled cells is 8.7%.
KeywordsEpidermal Growth Factor Receptor Basal Cell Squamous Epithelium Epidermal Growth Factor Receptor Expression Basal Cell Layer
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