Biliary cystadenoma(BCA)is a rare hepatic neoplasm.Although considered a benign cystic tumor of the liver,BCA has a high risk of recurrence with incomplete excision and a potential risk for malignant degeneration.Correct diagnosis and complete tumor excision with negative margins are the mainstay of treatment.Unfortunately,due to the lack of presenting symptoms,and normal laboratory results in most patients,BCA is hard to distinguish from other cystic lesions of the liver such as biliary cystadenocarcinoma,hepatic cyst,hydatid cyst,Caroli disease,undifferentiated sarcoma,intraductal papillary mucinous tumor,and hepatocellular carcinoma.Ultrasound(US),computed tomography(CT)and magnetic resonance imaging(MRI)may be necessary.They demonstrate intrahepatic cystic lesions with features such as mural nodules,varying wall thickness,papillary projections,and internal septations.Nevertheless,surgery is still the only means of accurate diagnosis.Definitive diagnosis requires histological examination following formal resection.We describe a57-year-old woman initially diagnosed with polycystic liver who was subsequently diagnosed with giant intra-hepatic BCA in the left hepatic lobe.This indicates that both US physicians and hepatobiliary specialists should attach importance to hepatic cysts,and CT or MRI should be performed for further examination when a diagnosis of BCA is suspected. Biliary cystadenoma (BCA) is a rare hepatic neoplasm. Already considered a benign cystic tumor of the liver, BCA has a high risk of recurrence with incomplete excision and a potential risk for malignant degeneration. Correct diagnosis and complete tumor excision with negative margins are the mainstay of treatment. Unfortunately, due to the lack of presenting symptoms, and normal laboratory results in most patients, BCA is hard to distinguish from other cystic lesions of the liver such as biliary cystadenocarcinoma, hepatic cyst, hydatid cyst, Caroli disease, undifferentiated sarcoma (US), computed tomography (CT) and magnetic resonance imaging (MRI) may be necessary. The hypothesis intrahepatic cystic lesions with features such as mural nodules, varying wall thickness, papillary projections, and internal septations. Yet, surgery is still the only means of accurate diagnosis. Definitive diagnosis requires histological examin We suggest a57-year-old woman initially diagnosed with polycystic liver who was followed diagnosed with giant intra-hepatic BCA in the left hepatic lobe. This indicates that both both US physicians and hepatobiliary specialists should be attached importance to hepatic cysts, and CT or MRI should be performed for further examination when a diagnosis of BCA is suspected.