ERBB2 and pancreatic intraductal papillary-mucinous neoplasm: Based on our current finding that 30–40% of PDA/IPMN patients were positive for HER2, trastuzumab therapy can be used for patients expressing HER2-dependent signaling pathway molecules, not just HER2 itself, determined by cancer tissue, and if possible, by culturing primary cancer cells from patients11.