Hepatoid adenocarcinoma of the gallbladder: Case report and review of the literature.

A rare case of hepatoid adenocarcinoma (HAC) of the gallbladder occurred in a 72-year-old man who presented with abdominal pain and was admitted to hospital. Ultrasonography and computed tomography revealed a mass in the gallbladder, multiple nodules in the liver and enlargement of the lymph nodes. He was diagnosed as having a gallbladder carcinoma with multiple liver and lymph node metastases. Cholecystectomy and partial hepatectomy was performed. Histologically, most of the mass in the gallbladder was composed of cells with eosinophilic cyto-plasm arranged in a trabecular pattern, which resembled hepatocellular carcinoma, but there was a component of well-differentiated adenocarcinoma in the mucosa. Immunohistochemically these hepatoid tumor cells were positive for Hepatocyte (Hepatocyte Paraffin 1: Hep Par1), which is considered highly sensitive and highly specific for hepatocyte differentiation. Based on these findings, this case was diagnosed as hepatoid adenocarcinoma of the gallbladder, which is generally a vary rare neoplasm in the literature, but should be included in the differential diagnosis of a mass in the gallbladder.