2013 年 83 巻 1 号 p. 204-205
A 58-year-old man presented with a one-year history of remittent abdominal pain in the left upper quadrant due to acute pancreatitis. MRCP showed a significantly dilated and tortuous main pancreatic duct, which was occluded by a 10 mm-sized hypointense oval mass at the pancreas head. Computed tomography revealed the mass to be hypodense in the pre-contrast phase and slightly enhanced in the delayed phase. The most likely diagnosis was a pancreatic protein plug. However, intraductal tubulopapillary neoplasm (ITPN) could not be ruled out because of its enhancement on CT, and further diagnostic tests were required. EUS showed the pancreatic duct was incompletely filled with a 10 mm-sized homogeneously hypoechoic round mass. On ERP, the mass was slightly mobile but could not be removed using biopsy forceps. Peroral pancreatoscopy (POPS) revealed that the mass comprised opaque white anhistous cotton-like matter. Based on these findings, we concluded that the mass was more likely to be a protein plug than ITPN, and removed it completely using basket forceps. On histopathology, the mass consisted of eosinophilic mucoid matter mixed with a few non-typical columnar epithelia. The patient’s abdominal pain was relieved after the procedure. Protein plug and ITPN can have similar characteristics on CT, MRCP, EUS and ERP. POPS is useful to differentiate between a protein plug and ITPN.