Undifferentiated (embryonal) sarcoma of the liver: ultrastructure, immunohistochemistry, and DNA ploidy analysis of two cases.

We describe the histopathologic, immunohistochemical, electronmicroscopic features, and DNA flow cytometric analysis of 2 cases of undifferentiated (embryonal) sarcoma of the liver. The tumor cells were found to be uniformly nonreactive to antibodies that identify cells belonging to the macrophagic-monocytic system. Focal expression of cytokeratin was an unexpected finding. We conclude that the observations are compatible with origin of this sarcoma from primitive mesenchyme. Uncertainty still exists about histogenesis, but the morphologic features of this neoplasm are quite characteristic. Both tumors demonstrate aneuploid stem lines with high S phase. Whether these findings are prognostically significant remains to be seen.