Pancreatic Mucinous Cystic Neoplasm Communicating with Main Pancreatic Duct: An Unrecognized Presentation of Pancreatic Mucinous Neoplasm?

Mucinous cystic neoplasms (MCNs) and intraductal papillary mucinous neoplasms (IPMNs) are two well recognized entities of precursor cystic lesions of pancreatic duct adenocarcinoma. The characteristic features of MCNs are the lined mucinous epithelium with underlying ovarian-type stroma, but without communication with the ducts, while that for IPMNs are the communication with the ducts but without the underlying ovarian-type stroma. Here we report a case of MCN communicating with the main pancreatic duct in a 68-year-old woman. The initial radiographic diagnosis was pancreatic IPMN with main pancreatic involvement and this was also confirmed during gross examination. Histologically, the pancreatic cystic neoplasm was lined with mucinous epithelium with underlying ovarian-type of stroma. Immunohistochemical stains confirmed that the stroma cells were positive for ER, PR, alpha-inhibin and focally positive for CD10. The final pathologic diagnosis was pancreatic mucinous cystic neoplasm communicating with the main pancreatic duct. To the best of our knowledge, this is the second pathology confirmed case of MCN communicating with the main pancreatic duct. A careful gross examination and bivalvation of the main duct communicating with the cystic neoplasm helps render the correct diagnosis. If more cases are reported in the future, the MCN communicating with duct could become a new entity of pancreatic mucinous neoplasm.