Figure 1  (A) Intestinalised epithelium in Barrett’s oesophagus (BO) with mild regenerative changes. Note that a mild degree of crypt distortion, budding and crowding is a normal component of metaplastic epithelium in BO. In one focus, there is mild stratification of the nuclei in the surface epithelium, but the nuclei are regular in shape, and the cells show a relatively low nuclear/cytoplasmic (N/C) ratio. (B) High-power photograph of marked regenerative changes in an area of mucosa close to the neosquamocolumnar junction. The epithelium shows prominent stratification of the nuclei, which includes the surface epithelium as well. A few intraepithelial neutrophils are present. Key features of regeneration in this case include tufting of the epithelial cells, low N/C ratio, prominent nucleoli and preservation of cell polarity. (C) An area of extreme regeneration in a freshly ulcerated mucosal surface. The crypt and surface epithelium show cells with increased N/C ratio, hyperchromaticity and mucin depletion. Note that the atypia in the monolayer of epithelium covering the freshly ulcerated surface is similar to that seen in the crypt. Biopsy specimens obtained from this area of the mucosa 6 months later showed no evidence of dysplasia.