Risk factors and impact of occult and skip metastasis in early-stage oral tongue squamous cell carcinoma.

Objectives: To investigate risk factors associated with occult lymph node metastases (ONM) and skip metastasis in early-stage oral tongue squamous cell carcinoma (OTSCC) patients. Meanwhile, to analyze the contribution of metastatic nodes to survival outcomes.

Materials and methods: 544 OTSCC patients who were clinically staged T1-T2N0 with pathologic results from May 2018 to January 2024 were enrolled. Those with ONM were divided into subgroups with or without skip metastasis. Clinical, laboratorial, radiological and pathological factors between groups were analyzed by using univariate analysis and multivariate logistic analysis. The association of tumor growth behavior with the metastatic pattern of lymph nodes was summarized. Additionally, disease free survival (DFS) among different groups were compared using Kaplan-Meier analysis.

Results: Tumor growth behavior was associated with ONM. Tumor thickness with a threshold of 6.4 mm was not inferior to histological depth of invasion in predicting ONM. Only 1.3% of patients had nodal involvement of neck level IV or V. The DFS of patients with ONM were significantly reduced than those without ONM (P < 0.001). The DFS between patients with and without skip metastasis exhibited no statistical significance(P = 0.246). The 1-year, 2-year recurrence rates of patients with or without ONM were 31.9%, 37.5%, 10.1% and 14.0%, correspondingly.

Conclusions: Tumor thickness with a threshold of 6.4 mm could be used as a preoperative predictor for ONM. Elective neck dissection of level I - III might be sufficient for early stage OTSCC patients. OTSCC patients with ONM should be closely observed during the first 2 years after surgery.

Clinical relevance: The risk of ONM in early stage OTSCC patients might be predicted by tumor thickness calculated on MR imaging. Elective neck dissection of level I - III could remove micrometastases timely and effectively.