Primary hepatic neuroendocrine neoplasm presenting as a massive cystic liver tumor mimicking mucinous cystic neoplasm of the liver: A case report and literature review.

Neuroendocrine neoplasms (NENs) preferentially arise in the bronchopulmonary tree or the gastrointestinal tract. Notably, primary hepatic NENs are extremely rare. The present study describes a case of hepatic NEN presenting as a giant hepatic cystic lesion. A 42-year-old woman presented with a large liver tumor. Contrast-enhanced abdominal computed tomography revealed a cystic tumor (18 cm) in their left liver. The tumor exhibited liquid components and mural solid nodules with enhanced effects. The lesion was diagnosed as mucinous cystic carcinoma (MCC) preoperatively. The patient underwent a left hepatectomy, and the postoperative course was uneventful. The patient has been alive without recurrence for 36 months postoperatively. The pathological diagnosis was NEN G2. This patient had ectopic pancreatic tissue in the liver and thus the ectopic pancreatic origin of the tumor was suspected. The present study describes a case of resected cystic primary NEN of the liver that was difficult to differentiate from mucinous cystic neoplasms. As primary liver NENs are extremely rare, further studies are needed to establish their diagnosis and treatment.