Abstract

Epstein-Barr virus (EBV) is frequently associated with nasopharyngeal lymphoepithe-liomas and certain types of lymphoma, and rare lymphoepithelioma-like carcinomas occuring in various of organs such as stomach, parotid gland, thymus and lung. We have investigated the possibility that EBV may be present not only in the rare type of nasopharyngeal carcinoma, but also in the typical nasopharyngeal carcinoma (NPC) of squamous cell type. Polymerase chain reaction (PCR) for the W fragment of EBV was performed for the detection of EBV DNA, and in situ hybridization was performed for the detection of latent EBV infection in formalin-fixed paraffin embedded surgical specimens with EBER probe. PCR for the variable number of tandem repeat (VNTR) region of the latent membrane protein-1 gene was also performed for the differentiation of the infected EBV subtype in the different tumors. Positive reactions of the EBV was shown in 18 (86 %) of 21 cases of NPC. These reactions were detected by all of the above cases only in the carcinoma tissue specimens. The frequency of EBV gene expression at the NPC was related to the histologic differentiation of the tumors: All of the 9 cases of the lymphoepitheliomas and 3 cases of poorly differentiated squamous cell carcinomas were positive for EBV, 5 out of 7 squamous cell carcinomas of moderate differentiation were positive for EBV, and 2 cases of the well differentiated squamous cell carcinomas were negative for EBV. The EBV found in the NPC has three different number of VNTR in the latent membrane protein gene-1. These results suggest that variable subtypes of EBVs are associated with the NPC and the association of RBV with NPC is late event in the nasopharyngeal carcinoma progression as evidenced by negative association in the preneoplastic lesion and frequent association in the more poor differentiated tumors.

• Keywords: Epstein-Barr virus, Nasopharynpeal carcinoma, LMP-1, VNTR