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 cytoplasm 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.
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