[Epithelioid sarcoma (immunomorphologic study)]

The paper presents immunofluorescence findings on the distribution of medium-sized vimentinic and cytokeratinic filaments in the cells of epithelioid sarcoma. Two morphologically different types of tumor cells have been shown to be distinguished by the pattern of their filament expression: fusiform fibroblastoid cells contain vimentin (a mesenchymal type of differentiation), but there is a coexpression of cytokeratin and vimentin (an epithelial type) in the so-called epithelioid cells. Double mesenchymal-and-epithelial differentiation of the cells makes it possible to suppose that this tumor is of mesodermal rather than mesenchymal origin as is generally accepted. The features found in the distribution of medium-sized filaments in the epithelioid sarcoma may be useful in the practical differential diagnosis of this tumor as compared to numerous morphologically similar neoplasms.