Undifferentiated sarcoma of the liver.

We report a case of undifferentiated (embryonal) sarcoma (USL) of the liver arising in a 5-year-old girl. She had abdominal pain and distension after a blow to her abdomen. Exploratory laparotomy disclosed a large tumor arising from left lobe of the liver, which showed a typical gross and microscopic appearance of USL. Immunohistochemically, the tumor cells reacted with antibodies against vimentin, cytokeratin, alpha-smooth muscle actin and muscle actin (HHF35). These immunohistochemical variety of the tumor cells may indicate unregulated gene expression of anaplastic tumor cells rather than divergent differentiation of immature cells as in hepatoblastoma.