Immunohistochemical and ultrastructural spectrum of hepatic sarcomas of childhood: evidence for a common histogenesis.

Hepatic sarcomas of childhood, which appear heterogeneous by standard morphologic criteria, pose challenging diagnostic and nosologic problems to the pediatric surgical pathologist. To identify features of these tumors that might help to clarify their origin and histologic classification, we studied 13 undifferentiated (embryonal) sarcomas of the liver (UESL) and two intrinsic hepatic rhabdomyosarcomas (RMS) using immunohistochemical and electron microscopic techniques. Immunohistochemical staining was performed on 14 tumors with use of commercially available antibodies against a variety of markers, as well as peanut agglutinin lectin; electron microscopy was performed on five UESL and both RMS. Desmin was expressed by 6/12 UESL and 2/2 RMS, muscle-specific actin by 5/12 UESL and 2/2 RMS, neuron-specific enolase by 1/12 UESL and 1/2 RMS, alpha-1-antitrypsin by 8/12 UESL and 1/2 RMS, and alpha-1-antichymotrypsin by 10/12 UESL and 1/2 RMS. Cytokeratin expression was observed in only four UESL. The overlap of immunohistochemical staining patterns and ultrastructural features shown by these obstensibly different tumors suggests a common histogenesis, perhaps from a multipotential mesenchymal stem cell.