A 72-year-old man was found to have a 40 mm mass in liver segment VIII during follow-up abdominal ultrasonography for type C viral hepatitis. Abdominal ultrasound showed a well-defined mass containing a cystic component, and computed tomographic hepatic arteriography showed heterogeneous enhancement except for cystic necrosis. Under a pre-operative diagnosis of atypical hepatocellular carcinoma (HCC), partial resection of liver segment VIII was performed. The encapsulated tumor consisted of a peripheral solid component with a central necrotic area. Histologically, the solid component had a two-layer structure, an HCC component in the external area and a sarcomatous component with neoplastic osteoid formation in the internal area, showing histological transition. Immunohistochemically, the HCC component was positive for hepatocyte antigen and negative for vimentin. The Ki-67 labeling index was found to increase from 5% to 58% with increasing histologic atypia. The sarcomatous component was positive for vimentin and negative for pan-keratin and hepatocyte antigen, with a Ki-67 labeling index of >90%. These findings led to a diagnosis of primary hepatic carcinosarcoma. Although previously reported patients with hepatic carcinosarcoma showed early metastasis with a very poor outcome, this patient has remained free of recurrence for 30 months, which is the longest recurrence-free survival time recorded for this type of cancer. Since relatively early-stage hepatic carcinosarcoma rarely seems to present as a small tumor showing a concentric growth pattern, we report this case with a review of the literature.
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