Prognostic impact of muscle invasion in buccal mucosa squamous cell carcinoma

Objective: The objective of the study was to assess the prognostic value of muscle invasion (MI), a key histopathological feature of tumor aggressiveness, and construct a superior prognostic prediction model combining the current TNM staging system.Materials and Methods: MI was analyzed in the whole-slide images from a total of 301 patients with primary buccal mucosa squamous cell carcinoma (BMSCC). Survival times of patients with/without MI were evaluated by Kaplan-Meier analysis. MI was further combined with the TNM staging system to explore its predictive value for prognosis. Moreover, 204 cases of head and neck carcinoma from the TCGA database were included.Results: MI positive rate reached to 76% (229/301) in patients with BMSCC. MI was associated with poor overall survival (p = 0.012) and disease-free survival (p = 0.022). The novel system (TNM staging combined with MI) revealed strong predictive performance, with the largest area under the curve (OS: p < 0.001, DFS: p < 0.004). MI and the established classification system were also had good predictive ability in the TCGA cohort.Conclusions: MI is an independent predictor of poor prognosis of BMSCC. The inclusion of MI in prediction system can augment the risk stratification of patients with oral squamous cell carcinoma and may assist in the clinical decision-making process.