Ultrastructure of nasopharyngeal carcinomas in American and Chinese patients

Fourteen carcinomas of the nasopharynx from Chinese and American patients were selected for electron-microscopic study in order to compare the fine structure of tumors from the two groups and to determine, if possible, the cell of origin. The undifferentiated tumors, by light microscopy, were of transitional cell, spindle cell, or lymphoepithelioma type. By electron microscopy, all three types were composed of cells forming keratin fibrils even though lacking recognizable squamous characteristics by light microscopy. It is suggested that many undifferentiated tumors of nasopharynx, especially lymphoepithelioma, are, in fact, squamous cell carcinomas.