Studies on ultrastructure of Ewing's sarcoma of bone

Seven cases of Ewing's sarcoma of bone were examined by electron microscopy. The presence of atypical junction complexes represents a new finding. The presence of a considerable amount of glycogen confirms previous observations. The ultrastructure of the tumor cells supports the conclusion that Ewing's sarcoma is a separate neoplastic entity different from reticulum cell sarcoma and hemangiomatous neoplasms. Cells in tissue cultures derived from biopsies of Ewing's sarcoma showed no growth pattern nor morphological appearance different from cells of other malignant mesenchymal tumors. No virus particles could be detected in the primary surgical specimens nor in the tissue cultures. Filamentous structures were observed in one tumor biopsy specimen. These structures could be interpreted as structures resembling developmental stages of some known viruses.