How is the diagnosis of epithelioid sarcoma made?

The diagnosis of epithelioid sarcoma is made by typical histologic features. The tumor is composed of malignant, eosinophilic, epithelioid and spindle cells arranged in nodules that often demonstrate central necrosis. Immunohistochemistry, special stains, and tissue culture are used to assist the diagnosis. The tumor cells demonstrate staining with both mesenchymal markers (vimentin), as well as epithelial markers (keratins and epithelial membrane antigen).