The "Silent" Upstaging: A Real-World Analysis of Discordance Between Clinical and Pathological Staging in Oral Squamous Cell Carcinoma and Its Implications for Treatment Intensification

Background: Accurate staging is the cornerstone of management in Head and Neck Squamous Cell Carcinoma (HNSCC). The 8th edition of the AJCC/UICC TNM staging system introduced Depth of Invasion (DOI) and Extracapsular Extension (ECE) to refine prognostic stratification. However, significant discrepancies often exist between pre-operative clinical staging (cTNM) and post-operative pathological staging (pTNM). This study evaluates the magnitude and clinical impact of this discordance in a real-world cohort. Methods: We conducted a retrospective analysis of 52 patients with biopsy-proven Squamous Cell Carcinoma (SCC) of the oral cavity and oropharynx treated at a tertiary cancer center. Patients underwent standard clinical staging followed by definitive surgical resection and neck dissection. Clinical (cT) and pathological (pT) stages were compared to calculate concordance rates, sensitivity, and specificity. High-risk pathological features, including DOI, Worst Pattern of Invasion (WPOI), Perineural Invasion (PNI), and Lymphovascular Invasion (LVI), were correlated with staging upgrades. Results: The overall concordance between cT and pT staging was only 23.0%. A profound "upstaging" phenomenon was observed, with 45.0% of patients receiving a higher pathological stage than determined clinically (e.g., cT2 to pT3). The primary driver of upstaging was the underestimation of DOI on clinical examination and imaging, which demonstrated a moderate negative correlation with Disease-Free Interval (DFI) (r = -0.35). Despite the high rate of pathological upstaging, adjuvant Chemoradiation (CRT) effectively neutralized the risk, resulting in comparable DFI between high-risk and low-risk cohorts (Mean DFI: 4.2 vs. 4.0 years; p > 0.05). Conclusion: Clinical staging significantly underestimates the extent of disease in nearly half of oral cancer patients, primarily due to the "invisible" nature of deep invasion (DOI). This "silent upstaging" underscores the critical need for advanced pre-operative imaging protocols (e.g., MRI with specific DOI sequences) and supports the routine use of adjuvant intensification in pathologically upstaged patients.