MUC6 and Barrett esophagus: 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.