## Aetiological Factors in Nasopharyngeal Carcinoma **Key Point:** Epstein-Barr virus (EBV) infection is the most significant aetiological factor in endemic regions, with >95% of non-keratinizing undifferentiated carcinomas showing EBV association. ### Aetiological Factors and Geographic Variation | Factor | Endemic Regions | Non-Endemic Regions | Mechanism | |---|---|---|---| | EBV infection | >95% association | Weak | Viral oncogenesis, LMP1 activation | | Tobacco/Alcohol | Cofactor | Primary factor | Direct carcinogenesis | | HPV infection | Weak (<10%) | Moderate (20-40%) | p16 inactivation, E6/E7 effects | | Genetic predisposition | Strong | Weak | HLA polymorphisms (HLA-A2, HLA-Cw6) | | Dietary factors | Salted fish, preserved foods | Not significant | Nitrosamine formation | **High-Yield:** EBV detection in tumour tissue (via in-situ hybridization for EBER) is a diagnostic criterion for nasopharyngeal carcinoma in endemic regions. The virus encodes latent membrane protein 1 (LMP1), which acts as a constitutive NF-κB activator, driving malignant transformation. **Clinical Pearl:** In non-endemic regions (North America, Europe), tobacco and alcohol are more prominent aetiological factors, and EBV association is weak. HPV-associated nasopharyngeal cancers are increasing in developed countries. **Mnemonic:** **EBV-NPC** = Epstein-Barr Virus drives Nasopharyngeal Carcinoma in endemic regions (Southeast Asia, Southern China, North Africa). 
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