Hepatic giant cell tumor is extremely rare, and only five cases have been reported of overt hepatocellular carcinoma, thus its histogenesis is controversial. Herein is reported a case of simultaneous hepatocellular carcinoma and osteoclast-like giant cell tumor in a single tumor. A liver tumor was found in a 74-year-old woman. Histologically the tumor consisted of two distinct components: mononuclear and multinuclear giant cells with osteoclastic giant cells, and a conventional hepatocellular carcinoma. The boundary between the two components showed transitional features. Immunohistochemistry showed that the osteoclast-like giant cells were CD68 and vimentin positive, but cytokeratin and AFP negative, while spindle-shaped cells were positive only for vimentin. In a portion of the hepatocellular carcinoma the cells were cytokeratin-8 and AFP positive. Ki-67 positivity was 10% for the hepatocellular carcinoma, 60% for the spindle-shaped cells, and 0% for the giant cells. It is possible that the tumor might have had a hepatocellular carcinoma origin, given the more highly proliferative sarcomatous changes and reactive osteoclast-like cells. This case provides a clue to the histogenesis of hepatic giant cell tumors.
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