Abstract
A 68-year-old woman was diagnosed with IgG4-related dacryoadenitis and sialadenitis in 2009. Administration of prednisolone in 2011 improved her symptoms and was later discontinued. Serum IgG4 levels were elevated in July 2017. CT scan revealed a round cyst surrounded by delayed perfusion in the tail of the pancreas. T1-weighted images on MRI scan showed the inside of the cyst had low intensity and the wall of the cyst had high intensity. On T2-weighted images, however, the inside of the cyst displayed high intensity and the wall of the cyst had low intensity. There were no apparent abnormalities in the main pancreatic duct. EUS disclosed a low echoic layer between the cyst and pancreatic parenchyma. ERP showed no communication between the pancreatic cyst and the main pancreatic duct. Laparoscopic distal pancreatectomy was performed with a preoperative diagnosis of mucinous cystic neoplasm or pancreatic endocrine neoplasm. Histopathological examination revealed that the cyst was surrounded by fibrosis and infiltration of chronic inflammatory cells, most of which were IgG4-positive plasma cells. Based on these findings, a revised diagnosis of focal autoimmune pancreatitis with storiform fibrosis and obliterative phlebitis around the cyst was made.
