KRT18 and cancer: Our results indicated that though CK18 protein expression varied among OSCC, it was abundant and stable in each OSCC; oesophageal squamous cell epithelium is intrinsically negative for CK8/18 expression and almost all cancer tissue specimens positive for CK8/18 expression contained more than 50% immuno-positive cells relative to the total number of cancer cells, though in a few cases CK8/18-positive cells constituted only 10–50% of cancer cells.