title: An ultrastructural study of extraskeletal Ewing's sarcoma.
abstract: A case of extraskeletal Ewing's sarcoma was studied ultrastructurally, cytologically, and cytochemically. This tumor was, as in that of osseous origin, composed of densely packed highly undifferentiated blastemic cells and so-called "darker cells." The principal tumor cells were undifferentiated cells, which were characterized by the scant cytoplasm containing a variable amount of glycogen granules, large round or oval nuclei with dispersed chromatin, and rudimentary cytoplasmic junctional complexes. Some of the darker cells seemed to show somewhat histiocytic differentiation from principal blastemic cells, but the others were degenerating. Cytochemically, no tumor cells revealed the presence of peroxidase, lysozymes, and Factor VIII-related antigen. It is likely that both Ewing's sarcomas of osseous and extraosseous origin are defined as undifferentiated sarcoma merely characterized by the presence of glycogen.
mesh_terms: D000293:Adolescent; D000941:Antigens / Q000032:analysis; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D003937:Diagnosis, Differential; D005169:Factor VIII / Q000032:analysis / Q000276:immunology; D005260:Female; D006003:Glycogen / Q000032:analysis; D006801:Humans; D007124:Immunoenzyme Techniques; D008854:Microscopy, Electron; D009132:Muscles / Q000648:ultrastructure; D012512:Sarcoma, Ewing / Q000648:ultrastructure*; D012983:Soft Tissue Neoplasms / Q000648:ultrastructure*; D014841:von Willebrand Factor
chemical_list: D000941:Antigens; D014841:von Willebrand Factor; D005169:Factor VIII; D006003:Glycogen