Mucins are glycoproteins that are common on the surfaces of many epithelial cells. Under normal circumstances, mucins are known to play a protective role for epithelial tissues. In addition, their involvement in the differentiation of the epithelium, modulation of cell adhesion, as well as cell signalling has also been proposed.¹ Two main families can be distinguished: secreted mucins or gel-forming mucins (MUC2, MUC5AC, MUC5B, MUC6), and membrane-bound mucins (MUC1, MUC3, MUC4, MUC12, MUC17).² Alterations in the expression and in the structure of mucins have been reported in both pre-neoplastic and neoplastic lesions.³ The production of MUC2 or MUC5AC has been correlated, by a majority of non-invasive type tumours, with the expansive growth of the tumours that display lower levels of invasion and metastasis.⁴ A broad histomorphological spectrum of ampullary carcinomas of Vater make a reproducible histological classification difficult. Ampullary carcinomas positive for MUC2 have been associated with intestinal type tumour, whereas MUC5AC-positive ampullary carcinomas were related to pancreaticobiliary type.^5–7 In ampullary carcinoma, immunohistochemical expression …