Epithelial characteristics of tumor cells in nasophasyngeal carcinoma.

Electron microscopy examination of nasopharyngeal carcinoma grafts in nude mice showed that the tumor cells retained their epithelial characteristics, as betrayed by the presence of keratin fibrils and of functional complexes at the cell membrane. Thus the cells positive for Epstein-Barr virus-specific nuclear antigen present in such grafts do represent the progeny of human epithelial tumor cells. C-type virus particles were observed in one tumor graft, indicating that epithelial human cells could pick up a mouse virus.