Undifferentiated (embryonal) sarcoma arising in conjunction with mesenchymal hamartoma of the liver.

The histogenesis of the undifferentiated (embryonal) sarcoma of the liver has been much debated. Originally, some investigators suggested that the tumor could originate from a mesenchymal hamartoma. Others doubted this hypothesis. The demonstration of alpha-1-antitrypsin in some tumors and of cytokeratins in others gave rise to new theories suggesting that the tumor was either a fibrous histiocytoma or a sarcomatoid hepatocellular carcinoma. As a new development in this search for the genesis of the undifferentiated (embryonal) sarcoma of the liver, this report describes a case that seems to substantiate, for the first time, the original hypothesis histogenetically linking the undifferentiated (embryonal) sarcoma and the mesenchymal hamartoma. The case is that of a 12-yr-old girl who developed an undifferentiated (embryonal) sarcoma of the liver in conjunction with a mesenchymal hamartoma. Furthermore, in places, the tumor exhibited striking epithelial differentiation as well as immunoreactivity for cytokeratins, alpha-1-antitrypsin and vimentin. Immunoreactivity for alpha-fetoprotein was limited to the areas of epithelial differentiation.