Prognostic impact of pathological skin and bone invasion in buccal mucosa squamous cell carcinoma.

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Background: Buccal mucosa squamous cell carcinoma (BMSCC) frequently presents with locally advanced disease and invasion of adjacent structures such as skin and mandible. Although bone and skin involvement upstage tumors to pT4a in AJCC staging, their independent prognostic significance in BMSCC remains uncertain. Clarifying their impact on survival may refine risk stratification and guide adjuvant treatment decisions. Methods: This retrospective cohort study included patients with histologically confirmed primary BMSCC treated with curative-intent surgery between January 2010 and December 2015 at a tertiary cancer center. Folow up was done by telephonic means. Inclusion criteria: pT3–pT4a tumors, any nodal status, M0 disease, and minimum 60-month follow-up or documented recurrence/death. Exclusion criteria: prior treatment elsewhere, distant metastasis at presentation, recurrent disease, or incomplete records. Clinicopathologic variables including pathological skin invasion, bone invasion pattern, lymph node status, perineural invasion (PNI), lymphovascular invasion (LVI), and extranodal extension (ENE) were analyzed. Survival analysis was performed using Kaplan–Meier method and Cox proportional hazards regression. Results: Out of 700 patients of all buccal mucosa cancers, Sixty-nine patients met inclusion criteria (median age 48 years; 96% males). Pathological skin invasion was present in 15.9%, and bone invasion in 59.4% (cortical 52.2%, deep intramedullary 5.8%). Lymph node positivity was 57.1%, ENE 29%, PNI 27.5%, and LVI 39.1%. On univariate analysis, pN status (log-rank p=0.003) and pathological skin invasion (p=0.034) were significantly associated with poorer DFS, whereas bone invasion was not (p=0.129). Multivariate Cox analysis identified pN status as an independent predictor of DFS (HR 12.93; 95% CI 1.46–114.19; p=0.021). Skin and bone invasion were not independently significant. No variable showed significant association with OS. Conclusions: In locally advanced BMSCC, nodal status remains the strongest independent predictor of DFS. Pathological skin invasion influences DFS on univariate analysis but loses significance after adjustment, while bone invasion does not independently impact survival.