Fig. 5. Histological and endoscopic (inset) appearances of Barrett's oesophagus. The main image is an H&E stain of an oesophageal biopsy taken from a patient with Barrett's oesophagus. The metaplastic glandular epithelium is on the left of the image. It shows clear evidence of intestinal differentiation with mucous containing goblet cells clearly visible (white arrow). When goblet cells are absent from the metaplastic epithelium, a gastric pattern of transdifferentiation is said to be present. The metaplatic epithelium demonstrates a sharp junction with the normal stratified squamous epithelium of the oesophagus visible on the right. The inset shows the characteristic appearance of Barrett's oesophagus at endoscopic examination. Note the well defined tongue of red columnar mucosa (black arrow) extending several centimeters into the oesophagus from the gastroesophageal junction. The normal oesophageal epithelium appears gray/white at endoscopy.