Which site within the oral cavity is most commonly affected by squamous cell carcinoma?

Explanation

## Site Predilection in Oral Cavity Squamous Cell Carcinoma **Key Point:** The lateral border of the tongue and floor of mouth are the most common sites for oral cavity SCC, accounting for approximately 50–60% of cases. These are considered "high-risk" sites due to thin, non-keratinized mucosa and pooling of carcinogens. ### Anatomical Distribution and Risk | Site | Frequency | Epithelial Type | Risk Level | Notes | |---|---|---|---|---| | Lateral tongue border | 25–30% | Non-keratinized | **High** | Direct contact with carcinogens; thin epithelium | | Floor of mouth | 20–25% | Non-keratinized | **High** | Pooling of saliva and carcinogens | | Soft palate complex | 10–15% | Non-keratinized | **High** | Posterior oropharyngeal junction | | Buccal mucosa | 10–15% | Keratinized | Moderate | Common site for betel quid-related SCC | | Hard palate | 5–10% | Keratinized | **Low** | Thick, keratinized epithelium; protective | | Dorsum of tongue | <5% | Keratinized | **Low** | Thick epithelium; less carcinogen contact | | Attached gingiva | <5% | Keratinized | **Low** | Keratinized; protective against carcinogens | ### Why Lateral Tongue and Floor of Mouth? **High-Yield:** Non-keratinized mucosa is thinner and more permeable, allowing deeper penetration of carcinogens. The floor of mouth is a "pooling" site where saliva and dissolved carcinogens accumulate, increasing mutagenic exposure. **Clinical Pearl:** Lesions at the lateral tongue border and floor of mouth often present at advanced stages (Stage III–IV) because they are less visible to the patient and may not cause early symptoms. ### Concept of "High-Risk" vs. "Low-Risk" Sites - **High-risk sites:** Non-keratinized mucosa (lateral tongue, floor of mouth, soft palate, ventrolateral surface of tongue) → thinner epithelium, higher carcinogen permeability, worse prognosis - **Low-risk sites:** Keratinized mucosa (hard palate, dorsum of tongue, attached gingiva) → thick protective epithelium, lower carcinogen penetration, better prognosis **Mnemonic:** **FLAT** — Floor of mouth, Lateral tongue border, Anterior pillar, Thin non-keratinized epithelium (high-risk sites). [cite:Robbins 10e Ch 7]