Intrahepatic peribiliary perivascular epithelioid cell tumor (PEComa) associated with heterotopic pancreas: A case report

Background: Perivascular epithelioid-cell tumor (PEComa) is a group of rare mesenchymal neoplasms that express myomelanocytic-cell markers and exhibit a wide variety of histopathological features. Although heterotopic pancreas has been reported to occur in the gastrointestinal tract, intrahepatic heterotopic pancreas has been reported only rarely. Case presentation: We present a case of intrahepatic PEComa that showed a strong regional correlation with the presence of heterotopic pancreas. An intrahepatic tumor and biliary dilatation was incidentally discovered during a diagnostic evaluation to investigate low-back pain in a 47-year-old Japanese male. Cholangiocarcinoma was suspected and a left hemihepatectomy performed. Histological examination revealed a 3 × 3.8-mm tumor in the neighboring B2 bile duct. Histological and immunohistochemical investigations revealed the presence of a PEComa and pancreatic acini within the tumor mass. PEComa in the hepatobiliary and pancreatic regions are extremely rare. The presence of heterotopic pancreas is also relatively uncommon. Conclusion: The strong regional association of these 2 lesions raises the possibility of a PEComa originating from heterotopic pancreas or from an irritable response caused by heterotopic pancreas.