The aim of this study was to investigate the expression of intermediate filaments (cytokeratin, vimentin), epithelial membrane antigen (EMA) and the presence of Epstein-Barr virus (EBV) DNA in undifferentiated nasopharyngeal carcinoma (NPC). A high incidence of nuclear signals in NPC was found in primaries and regional lymph node metastases (70%), using 35S-labelled probes of EBV plasmids for in-situ hybridization. Keratinizing squamous cell carcinomas were EBV-negative. All carcinomas were immuno-reactive for cytokeratin (KL-1). 45% of the carcinomas were positive for vimentin. The expression of epithelial membrane antigen was restricted to epithelial cells and reduced in NPC as compared to the distribution pattern of cytokeratin. Both EBV DNA and vimentin in NPC were present in 9 cases. However, in 5 cases NPC were harboring EBV but were not immunoreactive for anti-vimentin antibodies. In no case was a vimentin-positive NPC also EBV-negative. The identification of cytokeratin subtypes revealed no specific cytokeratin pattern in NPC. The expression of vimentin in NPC is not specific for EBV, but seems to reflect the loss of inter-epithelial contact in anaplastic carcinomas.
