Intraductal papillary mucinous neoplasms of the biliary and pancreatic ducts--a shape shifting outlook into an increasingly recognized disease.

Shape shifting, transformations and metamorphoses are common and fascinating themes in mythology, literature and folklore of different times. Among numerous examples of shape shifting, as physicians it is apt to mention The Strange Case of Dr. Jekyll and Mr. Hyde, by Robert Louis Stevenson, where the good Dr. Jekyll metamorphoses into the evil Mr. Hyde. Dr. Jekyll and Mr. Hyde: same character, two bodies with different morphology and with different biological behaviours. Those of us participating in the diagnosis and treatment of biliary and pancreatic tumours may find a similar scenario when considering the “strange case” of intraductal papillary mucinous neoplasms (IPMNs). IPMNs of the pancreas (IPMNs-P) and of the biliary tract (IPMNs-B) were initially described in Japan in the 1980s with the name of “mucin-secreting cancer of the pancreas” and “mucin-hypersecreting intrahepatic biliary neoplasms”, respectively. However, while IPMNs-P are widely recognized since the late 1990s, the term IPMN-B was used for the first time only in 2006