Prognostic impact of micrometastases and nodal status in early and advanced oral squamous cell carcinoma

Sentinel lymph node biopsy (SLNB) enhances staging and treatment of oral squamous cell carcinoma (OSCC) by enabling detection of micrometastases (Mi) and isolated tumour cells (ITCs). However, the prognostic significance of these microscopic tumour deposits remains unclear. This study aims to evaluate the impact of Mi, ITCs, and other nodal characteristics on survival and recurrence across all stages of OSCC. This retrospective cohort study included all patients with primary OSCC who underwent SLNB at Karolinska University Hospital between March 2019 and October 2024. Clinical and pathological TNM stages were recorded, including the presence of Mi, ITCs, and extranodal extension (ENE). Disease-free survival (DFS) and disease-specific survival (DSS) were analysed using Kaplan–Meier estimates and Cox proportional hazards models. A total of 259 patients were included. 66.4% presented with early-stage disease (cT1-T2N0). Recurrence occurred in 15.8% of cases. Increasing tumour stage and nodal burden were associated with poorer DFS and DSS (p < 0.0001). Mi was identified in 11.0% of patients with early-stage OSCC and in 3.4% of cases with advanced disease. Three-year DFS was 88.0% in pN0 disease, 100% for pN0itc, 73.2% for pNmi, and 57.9% in patients with macrometastasis (pN +). Tumour stage, nodal burden and ENE are strong predictors of DFS and DSS in OSCC. Patients with Mi had outcomes comparable to those with pN1 disease, whereas ITCs did not negatively affect prognosis. These findings support classifying Mi as metastatic disease, and underscore the value of SLNB in management across all stages of OSCC.