Primary Osteosarcoma of the Liver: Case Report and Literature Review.

Extraskeletal osteosarcoma is a rare, highly malignant, osteoid formation mesenchymal neoplasm in the absence of bone involvement, associated with exceptionally poor prognosis. It frequently arises in the soft tissues of the extremities or in the retroperitoneum, but rarely in visceral organ. We describe a primary osteosarcoma of the liver in a 70-year-old man who presented with an episode of fever, accompanied by abdominal discomfort, after an accident abdominal strike. Ultrasonography and computed tomography revealed a large heterogeneous mass with areas of dense calcification involving most of the right lobe of liver. Radiography did not show evidence of primary tumor or primary bone lesion at any other site. Histologically, the tumor showed an essentially similar appearance as osteosarcoma originating in the skeleton, comprised of polygonal or spindle shaped cells, along with abundant eosinophilic lace-like osteoids, or irregularly arranged bone trabeculae. Immunohistochemistry showed that the tumor cells were positive for vimentin, CD10, and focally for SMA and CD56, but negative for other lineage-specific markers. Thus, the findings favored a primary hepatic osteosarcoma. This patient received palliative chemotherapy to ease the signs of his sickness due to the large size of the tumor and he died 4 moths later.