We report a new case of solitary fibrous tumor (SFT) of the liver, an extremely rare neoplasm. Including the present case no more than ten cases are reported in the English-language literature. To date there is no definite proof of the origin of this tumor. Both mesothelial and fibroblas-tic genesis has been postulated. The monoclonal antibody CD 34 has recently been used for the characterization of SFT. SFT would appear to be histogenetically related to a CD 34 - positive fibroblastic stem cell. A 61-year-old woman was admitted to our department with epigastric and right hypochondriac pain, weight loss, and hypoglycemia. Ultrasonography and computed tomography demonstrated a large heterogeneous mass in the right hepatic lobe. A right hepatectomy was performed. The tumor weighed 2850 g and microscopic section revealed a peculiar random pattern, the so-called patternless pattern of spindle tumor cells separated by abundant thick collagen bands. The tumor presented a number of highly cellular areas composed of plump spindle cell with hyperchromatic nuclei and rare mitotic figures. Ninety percent of the neoplastic cells displayed strong immunoreactivity for CD 34/My 10. The postoperative course was uneventful and the patient is alive and well without recurrence 6 years after surgery.