GPC1 and pancreatic neoplasm: Importantly, CA19–9 serum levels exhibited limited ability to distinguish between patients with intraductal papillary mucinous neoplasm (PCPL) and healthy controls, whereas GPC1-positive serum exosomes yielded 100% sensitivity and specificity across all stages of pancreatic cancer (e.g., carcinoma in situ, stage I, and stages II-IV) (28).