MUC1 and neoplasm: In addition to standard histopathological examination of the resected pancreatoduodenectomy specimens, immunohistochemical examination with antibodies directed against differentiation markers may be applied to discriminate between tumours of pancreatobiliary and intestinal-type differentiation.6,8,9,17–26 No single marker has so far been found to distinguish reliably between the two histological types and several differentiation markers are often used in combination.6,22–26 The differentiation markers most often used are cytokeratin (CK) 7 and CK20, and the mucin proteins MUC1 and MUC2.