Prognostic Significance of Tumor Budding in Early Oral Tongue Squamous Cell Carcinoma with Shallow Depth of Invasion

Purpose This study aims to explore prognostic factors for late cervical lymph node metastasis in oral tongue squamous cell carcinoma (OTSCC) with pathological depth of invasion (pDOI) ≤ 3 mm, which, despite shallow invasion, may still be associated with unfavorable oncological outcomes. We emphasize tumor budding (TB) as a potential risk indicator. Methods We retrospectively analyzed 107 patients with pT1–T2N0 OTSCC and pDOI ≤ 3 mm. Variables associated with late cervical lymph node metastasis were first evaluated using univariate analysis. Significant factors were then tested in a multivariate Cox proportional hazards model. We also assessed whether combining pDOI and tumor budding (TB) improved predictive performance. Results Neck recurrence occurred in nine patients (8.4%) within 3 years. Multivariate analysis identified TB ≥ 5 as an independent prognostic factor for late cervical lymph node metastasis. The combination of pDOI ≥ 2.0 mm and TB ≥ 5 improved sensitivity and negative predictive value for identifying high-risk cases. Conclusion In OTSCC with shallow pDOI (≤ 3 mm), TB is a significant prognostic factor for late cervical lymph node metastasis. Incorporating TB into routine pathological evaluation may improve risk stratification in early-stage cases and inform postoperative surveillance strategies.