Macrocystic serous cystadenoma mimicking branch duct intraductal papillary mucinous neoplasm.

A 29-year-old woman was referred to our hospital with a pancreatic cystic tumor diagnosed by computed tomography and magnetic resonance imaging. Endoscopic retrograde cholangiopancreatography was performed, wherein macrocystic serous cystadenoma of the pancreas was diagnosed. It was decided to observe the progress of the disease. The tumor diameter increased over 18 months to > 50 mm. Its growth rate was slower than the average rate of serous cystadenoma described in previous reports, but its form become warped and shaped like bunches of grapes. A branch duct variant of intraductal papillary mucinous neoplasm could not be excluded. Laparoscope-assisted distal pancreatectomy was performed, and the pathological diagnosis was macrocystic serous cystadenoma. Some macrocystic serous cystadenomas are like an intraductal papillary mucinous neoplasm, and differential diagnosis is very difficult. The macrocystic serous cystadenoma is a rare lesion, but it should be considered when diagnosing cystic tumors of the pancreas.