## Most Common Site of Basal Cell Carcinoma **Key Point:** The face and neck region accounts for approximately 80–90% of all basal cell carcinomas, making it the overwhelmingly most common site. ### Anatomical Distribution | Site | Frequency | Reason | | --- | --- | --- | | Face and neck | 80–90% | Maximum cumulative sun exposure; thin, sensitive skin | | Trunk and back | 10–15% | Moderate sun exposure; thicker skin | | Lower extremities | 3–5% | Minimal sun exposure; protected by clothing | | Scalp and ears | Included in face/neck | High-risk areas within the head region | **High-Yield:** Within the face, the most frequent sites are: - Nose (25–30% of all BCCs) - Cheeks - Forehead - Periocular region **Clinical Pearl:** The "H-zone" (horizontal line across the bridge of nose and vertical line down the midline of the face) represents the area of maximum sun exposure and highest BCC incidence in Indian patients. ### Pathophysiology Ultraviolet B (UVB) radiation causes DNA damage (thymine dimers) in basal keratinocytes. The face and neck receive the most direct and cumulative solar exposure over a lifetime, explaining the predilection for these sites. **Warning:** Do not confuse site distribution with risk factors — while sun exposure is the primary driver, the face is exposed year-round, whereas trunk exposure is seasonal and often protected by clothing.
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