Even in ‘specialised epithelium’, there are multiple cell lineages: columnar cells resembling gastric foveolar cells containing MUC1, MUC5AC and mucus secreting cells expressing MUC6—mucin core proteins characteristic of gastric epithelium,6, 7 and goblet cells, with MUC2 and MUC3—seen in intestinal epithelium.8 Thus, the so-called ‘specialised epithelium’ of Barrett's oesophagus, often compared with intestinal metaplasia, shows evidence of gastric lineage differentiation as well as intestinal differentiation. This evidence concerns the gene MUC5AC and Barrett esophagus.