Which histological type accounts for approximately 95% of nasopharyngeal carcinomas in endemic regions like Southeast Asia and Southern China?

Explanation

## Histological Classification of Nasopharyngeal Carcinoma **Key Point:** Non-keratinizing undifferentiated carcinoma (WHO Type III) is the predominant histological type in endemic regions, accounting for ~95% of cases in Southeast Asia, Southern China, and North Africa. ### WHO Histological Classification | Histological Type | Frequency (Endemic) | EBV Association | Geographic Pattern | |---|---|---|---| | Non-keratinizing undifferentiated | ~95% | Very strong (>95%) | Endemic regions | | Keratinizing squamous cell | ~5% | Weak | Non-endemic regions | | Adenocarcinoma | <1% | Weak | Rare globally | | Small cell carcinoma | <1% | Weak | Rare globally | **High-Yield:** The non-keratinizing undifferentiated type is strongly associated with EBV (Epstein-Barr virus) infection, which is a major aetiological factor in endemic areas. This type is also called **WHO Type III** or **lymphoepithelioma**. **Clinical Pearl:** The keratinizing type is more common in non-endemic regions (e.g., North America, Europe) and has weaker EBV association, suggesting different aetiological pathways. **Mnemonic:** **NUDE** = Non-keratinizing Undifferentiated (most common in endemic regions, strongly EBV-associated).