Ectopic hepatocellular carcinoma mimicking a retroperitoneal tumor: A case report

Background An ectopic hepatocellular carcinoma (EHCC) arises from the ectopic liver which is defined as a hepatic organ or tissue not connected to surrounding tissues. EHCC is a rare disease and it is difficult to diagnose preoperatively. Furthermore, the clinical features are not fully elucidated. Case summary A retroperitoneal tumor (6 cm) was located at the dorsal side of the pancreas head on abdominal ultrasonography in an 81-year old woman positive for hepatitis C virus antibody. Contrast enhanced-computed tomography and gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging showed viable HCC patterns with early enhancement and delayed washout. The tumor markers - serum alpha-fetoprotein and alpha-fetoprotein-L3% - were increased to 30.1 ng/mL and 83.1%, respectively. Protein induced by vitamin K absence or antagonist-II was within normal levels (17 mAU/mL). Positron emission tomography-computed tomography showed strong accumulation into the tumor (Standardized Uptake Value max: 13.8), and the tumor cytology following endoscopic ultrasound-guided fine needle aspiration showed poorly differentiated carcinoma. Tumor extirpation was performed, and operative findings showed that the retroperitoneal tumor was disconnected from the pancreas and the liver. Swollen lymph nodes near the tumor were histologically normal. On histological examination, the tumor was finally diagnosed as EHCC with Arginase-1 positive expression. Conclusion We report our experience of a rare EHCC which was difficult to diagnose, and we present a review of the literature.