## Histological Types of Nasopharyngeal Carcinoma **Key Point:** Undifferentiated (non-keratinizing) squamous cell carcinoma is the most common histological type of nasopharyngeal carcinoma (NPC), accounting for 60–70% of cases globally, and >90% in endemic regions like Southeast Asia and southern China. ### WHO Classification & Epidemiology | Histological Type | Frequency | EBV Association | Geographic Pattern | | --- | --- | --- | --- | | **Undifferentiated SCC (non-keratinizing)** | 60–70% (>90% endemic) | Strong (>95%) | Worldwide, especially endemic | | Differentiated SCC (keratinizing) | 20–30% | Weak (10–20%) | North Africa, Middle East | | Basaloid SCC | <5% | Moderate | Rare | | Adenocarcinoma | <5% | Weak | Rare | | Small cell carcinoma | <2% | Weak | Very rare | | Lymphoma | <2% | Variable | Rare | **High-Yield:** The undifferentiated type is strongly associated with **Epstein–Barr virus (EBV)** infection, particularly in endemic populations. EBV serology (anti-VCA-IgA, anti-EBNA-IgA) is used for screening and prognosis in high-risk regions. ### Clinical Pearls **Clinical Pearl:** Undifferentiated NPC typically presents with: - Cervical lymphadenopathy (80% of cases) — often the first sign - Epistaxis or blood-stained nasal discharge - Unilateral otitis media with effusion (Eustachian tube obstruction) - Cranial nerve involvement (CN II–VI) in advanced disease **Mnemonic:** **UNDIFFERENTIATED = EBV-driven, endemic, early nodal spread** ### Why Undifferentiated Type Dominates 1. **Strong EBV link** — latent EBV infection in nasopharyngeal epithelium drives malignant transformation, particularly in genetically susceptible populations (HLA-A2, HLA-A201) 2. **Endemic clustering** — southern China, Southeast Asia, North Africa, Inuit populations show 20–50× higher incidence due to combined viral, genetic, and dietary (salt-cured foods, nitrosamines) factors 3. **Age of onset** — typically 40–60 years; undifferentiated type can present slightly earlier than keratinizing variants **Warning:** Do not confuse keratinizing SCC (more common in non-endemic regions, weaker EBV link) with undifferentiated SCC (endemic, strong EBV). The exam will test this distinction. [cite:Harrison 21e Ch 107]
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