## Histological Types of Nasopharyngeal Carcinoma **Key Point:** Squamous cell carcinoma (non-keratinizing, undifferentiated) is the most common histological type of nasopharyngeal carcinoma globally, accounting for approximately 95% of cases, with even higher prevalence in endemic regions like Southeast Asia and Southern China. ### WHO Classification & Epidemiology | Histological Type | Frequency | EBV Association | Geographic Pattern | |---|---|---|---| | SCC Non-keratinizing (undifferentiated) | 95% | Strong (>95%) | Endemic areas (SE Asia, Southern China, North Africa) | | SCC Keratinizing | 3–5% | Weak | Non-endemic areas | | Adenocarcinoma | 1–2% | Absent | Rare globally | | Small cell carcinoma | <1% | Absent | Very rare | **High-Yield:** The undifferentiated (WHO Type III) variant is strongly associated with **Epstein–Barr virus (EBV)** infection. EBV serology (VCA-IgA, EBNA-IgA) is used for screening and monitoring in endemic regions. **Clinical Pearl:** The keratinizing type is more common in non-endemic regions and has weaker EBV association. In India, the undifferentiated type predominates in endemic pockets (Tamil Nadu, Andhra Pradesh). ### Why Undifferentiated Type Dominates 1. **EBV oncogenic potential** — latent EBV infection in nasopharyngeal epithelium drives malignant transformation 2. **Genetic susceptibility** — HLA polymorphisms in endemic populations 3. **Environmental cofactors** — salt-cured foods, tobacco, occupational exposures **Mnemonic:** **UNCA** = **UN**differentiated, **C**arcinoma, **A**ssociated with EBV (most common). [cite:Harrison 21e Ch 101]
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