Solitary extrahepatic hepatocellular carcinoma without a primary lesion in the liver is rare and unique. In such patients, in addition to hepatocellular carcinoma, hepatoid adenocarcinoma, hepatoid teratoma, and hepatoid yolk sac tumor must be considered as differential diagnoses, and patients must be investigated in detail by histopathological studies with immunohistochemistry, especially using epithelial markers for which tumor cells are generally negative in hepatocellular carcinoma. A case with a solitary neoplasm of the vertebrae, which was diagnosed histopathologically as hepatocellular carcinoma, without a primary lesion is presented. The primary lesion was not identified even on autopsy, and the liver was pathologically almost normal. Given the review of the literature and circumstantial evidence, we would like to propose a bold new hypothesis that hepatocellular carcinoma might primarily originate from bone marrow.
Keywords: Carcinogenesis; Differential diagnoses; Hepatocellular carcinoma; Unknown primary.
© 2022. Japanese Society of Gastroenterology.