Aim This study was undertaken to evaluate the expression of claudins 7 and 18 in pancreatic ductal adenocarcinoma.

Methods and results Material tested included 111 operated samples and 47 additional biopsy samples consisting of 26 cases of pancreatitis, 3 cases of pancreatic intraepithelial neoplasia and 18 ductal adenocarcinomas. Samples were stained with antibodies to claudins 7 and 18 and analysed for membranous and cytoplasmic expression. Membrane bound claudin 7 and 18 expression was detected in 62 of 105 (59%) and 78 of 111 (70%) cases, respectively. Membrane bound claudin 7 and 18 were associated with large or intermediate neoplastic ducts (p=0.01, p=0.002, respectively). Well differentiated pancreatic adenocarcinomas displayed more cases with membrane bound claudin 7 or 18 immunopositivity (p=0.003, p=0.03, respectively). All pancreatic intraepithelial neoplasias studied expressed membrane bound claudin 18. Membrane bound claudin 7 or 18 positivity was not associated with survival (p=0.17, p=0.98). In the biopsy cases membrane bound claudin 18 had 100% specificity and 51% sensitivity for a tumour marker.

Conclusion Claudin 7 and 18 expression is related to gland size of neoplastic cells and is especially found in tumours with intermediate and large ducts and well differentiated tumours. Membrane bound claudin 18, when present, is a useful marker for diagnosis of pancreatic cancer. Claudins 7 and 18 were not associated with patient survival or spread of tumours.