Detection of EBV and HPV in Nasopharyngeal Carcinoma by In Situ Hybridization

Nasopharyngeal carcinoma, particulary tumors endemic to the Far East, commonly harbors Epstein-Barr virus. The detection of nuclear antigen associated with EBV and viral DNA in NPC cells have revealed that EBV can infect epithelial cells and is associated with transformation. Human papilloma virus is an epitheliotrophic oncogenic virus that has been detected in a variety of head and neck tumors. This retrospective study was undertaken to investigate the prevalence of EBV and HPV infection subtypes 6/11 and 16/18. in 20 patients with nasopharyngeal carcinoma by in situ hybridization. 16 case (80%) were classified as undifferentiated carcinoma (WHO type III) and 4 (20%) as non keratinizing SCC (WHO type II). According to AJCC (American Joint Committee of Cancer) system the clinical stage at presentation was available for 20 patients: 10% presented with stage I, 5% presented with stage II, 25% presented with stage III and 60% presented with stage IV. 55% of the cases presented with palpable cervical lymph node metastasis. In situ hybridization for EBER was performed with a fluorescien-conjugated PNA probe. EBER expression was detected in 19 of the 20 evaluated nasopharyngeal carcinoma (95%). Thyramid signal amplification of ISH was performed for HPV DNA subtype 6/11 and 16/18 with a biotinylated DNA probe. Two of 20 NPC (10%) contained HPV 6/11 sequences and two of 20 NPC (10%) contained HPV 16/18 sequences and combined EBV and HPV infection was detected in 3 of the 20 (15%) patients. In this study a high correlation of almost 95% was observed between EBV and NPC type II & III, in WHO classification. Combined EBV and HPV infection was detected only in 15% of patients. There seems to be a geographic difference in positive rates between our results and those obtained from high-risk area.