Epithelioid osteosarcoma of bone. Immunocytochemical evidence suggesting divergent epithelial and mesenchymal differentiation in a primary osseous neoplasm.

Abstract

The combination of a primary osteosarcoma of bone with a second carcinomatous cell type has been recognized, although immunohistochemical studies currently have not been performed in an attempt to understand the histogenesis of such a tumor. In this report, the authors performed immunohistochemical studies on a primary osseous carcinosarcoma. Using a biotin-streptavidin peroxidase conjugate technique, the expression of keratin, epithelial membrane antigen, and vimentin was analyzed. The epithelial cells expressed cytokeratin and epithelial membrane antigen but did not express vimentin. The mesenchymal cells strongly expressed vimentin, and only rare cells expressed cytokeratin. The clinical, morphologic, and immunophenotypic data in this instance strongly suggest divergent differentiation of a primitive multipotential uncommitted stem cell in a primary osseous tumor.