Abstract

A soft tissue tumor of a 17-year-old Korean girl was observed light and electron microscopically, which revealed the featured compatible with extraskeletal Ewing's sarcoma. The identity to Ewing's sarcoma of osseous origin was extended to the ultrastructural level. The tumor was composed of two types of cells, namely, principal cells and secondary cells. Although multiple sections of the tumor were examined, there was no definite evidence to indicate the cell of origin on the ultrastructural study.