MSLN (Mesothelin) is a cell-surface glycoprotein with normal expression in peritoneum, pleura, and pericardium, but with overexpression in a variety of cancers, including mesothelioma, pancreatic, lung, gastric, and ovarian cancers. It encodes a preproprotein that is proteolytically processed to generate two protein products, megakaryocyte potentiating factor and mesothelin. Mesothelin (MSLN) is an attractive antigen for chimeric antigen receptor (CAR) T therapy and the epitope selection within MSLN is essential. MSLN is an ideal cancer antigen for targeted immunotherapy. Diseases associated with MSLN include Benign Mesothelioma and Malignant Pleural Mesothelioma.