A study on direct metastasis to levels III, IV in oral tongue squamous cell carcinoma

Objective: This study aimed to determine the frequency and specific metastatic patterns of direct metastasis to levels III and IV in oral tongue squamous cell carcinoma (OTSCC) among Japanese individuals. Methods: We conducted neck dissections on 319 patients at our department from January 2001 to December 2020. Of these, 220 patients with histopathological evidence of lymph node metastasis were included in the study. Lymph node metastases were categorized by level to elucidate the metastatic patterns. Additionally, metastatic sites within level III were identified as either anterior or posterior to the internal jugular vein, and these findings were compared between the direct metastatic group and the non-direct metastatic group. Results: Among the patients, 13 experienced direct metastases to level III or IV. Specifically, 12 patients had metastases at level III, and one patient had metastases at both levels III and IV, constituting 5.9 % (13/220) of those with cervical lymph node metastasis in OTSCC. No patients exhibited direct metastases solely to level IV. Within level III, the direct metastasis group showed a significantly higher incidence of metastasis anterior to the internal jugular vein (p = 0.03). Conclusions: Direct metastasis to levels III and/or IV occurred in 5.9 % of the cases. Although elective neck dissection up to level III is generally sufficient, metastasis to level IV, while infrequent, can occur. Therefore, vigilant follow-up with attention to the lower neck regions is crucial.