Undifferentiated (embryonal) sarcoma of the liver. Epithelial features as shown by immunohistochemical analysis and...

The cell differentiation properties of two undifferentiated (embryonal) sarcomas of the liver (USL), one in a 9-year-old boy and one in a 23-year-old man, were studied by immunohistochemistry and electron microscopic examination. Both tumors showed a part pleomorphic pattern and a part myxoid spindle cell sarcomatous pattern. An electron microscopic examination showed some tonofilament-like bundles of intermediate filaments and cell junctions in one case, suggesting the presence of epithelial differentiation in that tumor. An immunohistochemical analysis showed a large number of cytokeratin-positive neoplastic cells in both cases as studied with two different monoclonal antibodies, and most cells were positive for vimentin. No cells showed desmin, glial fibrillary acidic protein, or epithelial membrane antigen (EMA). Due to the presence of cytokeratin immunoreactivity, the possibility was considered that these tumors would represent anaplastic sarcomatoid variants of hepatocellular carcinoma. The tumor cells showed cytoplasmic alpha-1-antitrypsin (AAT) positivity, and were negative for alpha-fetoprotein. Because the immunoreactivity of AAT is widespread in different types of tumors, it is not possible to conclude that the AAT positivity would indicate the hepatoma nature of USL; however, this remains a possibility, especially when considering that in vitro transformed hepatocytes have been shown to be capable of forming sarcomatous tumors.