A Rare and Difficult Diagnosis: A Case of Hepatoid Carcinoma of the Gallbladder.

Extrahepatic metastasis of hepatocellular carcinoma is usually associated with extensive intrahepatic lesions. Hepatoid adenocarcinoma is a rare variant of extrahepatic malignant adenocarcinoma that exhibits remarkable histological and immunohistochemical similarity to hepatocellular carcinoma, which can result in an underestimated diagnosis. This case report describes a patient with a newly found gallbladder polyp. Following cholecystectomy, the initial histological and immunohistochemical evaluation suggested a metastasis of hepatocellular carcinoma. However, after multiple scans, no primary intrahepatic lesion was found. A subsequent review of the gallbladder specimens showed negative staining for CK7 and CK19, leading to a diagnosis of hepatoid carcinoma of the gallbladder.