[Ultrastructure of a sacral chordoma]

The ultrastructural findings in a sacrococcygeal chordoma are presented. The tumor cells showed various types of vacuoles. The presence of two types of membrane-bound dense bodies and an intracellular fibrillar material were other striking features of the tumor. Most of the present findings are in agreement with other studies and suggest a double differentiation of the tumor cells, epithelial and mesenchymatous. It is believed that the extracellular substance forming the tumor matrix is produced by mature tumor cells. Despite the pleomorphism and the variation of cell components, it is suggested that the stellate, intermediate and physaliferous cells, constitute the same cell at different stages of maturation.