On the origin of cardiac mucosa: A histological and immunohistoc-hemical study of cytokeratin expression patterns in the developing esophagogastric junction region and stomach

Figure 3 Tubular esophagus. A: Esophageal ciliated epithelium at 20-wk GA. The immunostaining is for CK5 and is more intense in the basal and intermediate cell layers than in the superficial cell layer (OM ×400); B: Esophageal squamous epithelium in a 3-wk-old neonate. The immunostaining is for CK13 and is absent in the basal cell layer and diffuse moderate to strong in the intermediate and superficial cell layers (OM ×200); C: Esophageal simple columnar epithelium at 20-wk GA. To the left: parietal cells with roughly triangular shape and highly acidophilic cytoplasm (ESP, arrowhead). To the right: no discernible parietal cells are present (ESN, H&E, OM ×400); D: Esophageal simple columnar epithelium at 20-wk GA. The immunostaining is for CK7 and shows moderate positivity at the mucosal surface and deep in the glands (arrowhead and arrow, respectively, OM ×200); E: Esophageal simple columnar epithelium at 20-wk GA (same case as in Figure 3D). The immunostaining is for CK20 and shows patchy positivity of the superficial part of the mucosa (surface and pit epithelium: arrowhead and arrow, respectively, OM ×200).