Impact of Anatomical Subsite on Achieved Surgical Margins in Head and Neck Basal Cell Carcinoma

<b>Introduction:</b> Basal cell carcinoma (BCC) most commonly affects the sun-exposed head and neck skin, where oncologic clearance must be balanced against functional and cosmetic outcomes. Whether anatomical subsite independently influences achieved histopathological margins is clinically relevant for ENT practice.<b>Aim:</b> To assess the association between tumor location and achieved surgical margins (minimum lateral and deep) in head and neck BCC, and to identify subsites most prone to narrow/positive margins and adverse histopathological features.<b>Materials and methods:</b> Retrospective single-centre study of surgically excised head and neck BCCs treated at the Military Medical Institute (Warsaw) between 2018 and 2021. Variables included minimum lateral/deep margins, maximum tumor dimension, depth of invasion, ulceration, perineural invasion, inflammatory response, Demodex, post-solar hyperplasia, and coexisting lesions (Bowen's disease, SCC, melanoma). Subsites: forehead, nose, periorbital, perioral, scalp, temporal, periauricular. Kruskal-Wallis and χ/Fisher's exact tests were used (α = 0.05).<b>Results:</b> Location significantly influenced margins and histopathology. Periorbital lesions had the largest median deep margins, whereas the nose had the smallest ones. Forehead tumors achieved the widest lateral margins, while periorbital/perioral subsites the narrowest ones. Perioral lesions showed the greatest depth of invasion; the temporal region the smallest one. Scalp tumors presented with the largest maximum dimension. Nasal lesions most frequently exhibited perineural invasion and ulceration. Demodex was most common on the nose; coexisting Bowen's disease and melanoma also clustered nasally, while SCC clustered periauricularly.<b>Discussion:</b> Findings reflect local anatomy and organ-preserving constraints in central facial subsites and support location-tailored surgical planning.<b>Conclusions:</b> Anatomical subsite is a key determinant of achievable margins and adverse features in head and neck BCC, arguing for subsite-adapted strategies and audits of guideline adherence by location.