Morphological evidence of viruses in nasopharyngeal carcinoma?

Human tumor tissue from patients with nasopharyngeal carcinoma was investigated electron microscopically before and after transplantation to nude mice. Although we were unable to find distinct herpes type-C particles in human tissue, these particles could be seen following tissue transplantation to nude mice in two cases. The findings are discussed as to whether those particles are either endogenous in nude mice or expressed by the tumor tissue as a consequence of transplantation.