Background: 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.
Methods: 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.
Results: 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.
Conclusions: 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.