MSLN and pancreatic ductal adenocarcinoma: Mesothelin (MSLN) is a validated immunotherapy target that is highly overexpressed on the surface of common epithelial cancers including ovarian cancers, epithelial malignant mesotheliomas, ductal pancreatic adenocarcinomas, and lung adenocarcinomas, while expressed at relatively low levels only in mesothelial cells lining the pleura, pericardium, and peritoneum in healthy individuals[6-9].