Updated project metadata. The increased number of pancreatic cyst lesions (PCLs) have been detected through the development of abdominal imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and endoscopic ultrasound (EUS). However, accurate classification of cystic lesions is difficult because of the lack of standardized diagnostic methods, and thus potentially unnecessary surgical resection has been performed on pancreatic cyst patients. Among four most common types of cystic lesions of pancreas, intraductal papillary mucinous neoplasms (IPMNs), mucinous cystic neoplasms (MCN), serous cystic neoplasms (SCN), and solid pseudopapillary neoplasms (SPNs), IPMNs, the precursor lesion of pancreatic cancer, have been detected most frequently, and are subdivided into low-grade dysplasia (LGD), high-grade dysplasia (HGD), and invasive IPMN in accordance with their malignancy. To discover the potential biomarkers of the histological grades of IPMN, we investigated pancreatic cyst fluid proteins that are differentially expressed in accordance with the IPMN malignancy by LC-MS/MS analysis.