CLDN5 and pancreatic neuroendocrine tumor: Claudin-5 is significantly positively expressed in pancreatic solid-pseudopapillary tumor cell membranes (SPN), but not in pancreatic neuroendocrine tumors (P-NET), and combined IHC detection of claudin-5 and intercellular adhesion molecule, CD99, is required for the diagnosis of SPN and P-NET (42).