A case of mandibular gingival squamous cell carcinoma with mandibular lymph node metastasis

Metastasis of oral cancer to the mandibular lymph node (MLN) is rare, particularly in the early stages. Furthermore, no consensus about surgical treatment of metastasis to the MLNs exists. Herein, we describe a case of MLN identified early on computed tomography (CT) when the patient was initially diagnosed with squamous cell carcinoma of mandibular gingiva. Since no evident malignant findings on positron emission tomography-CT (PET-CT) or cervical ultrasonography were observed, the case was regarded as normal anatomy without metastasis. A diagnosis of mandibular gingival cancer (cT2N0M0) was made; marginal mandibulectomy was performed. However, three months later, contrast-enhanced CT images revealed an enlarged 12 mm × 7 mm MLN, and fluorodeoxyglucose (FDG) accumulation (SUV max: 3.9) was observed in both the MLN and submandibular lymph nodes on FDG-PET/CT. Therefore, we performed radical neck dissection including the MLN. Extra-nodal extensions were observed in the submandibular lymph nodes. Accordingly, weekly cisplatin at a dose of 40 mg/m² combined with radiotherapy (66 Gy) was performed as post-operative treatment. The MLN is an intercalated lymph node that may not be present in some patients or the lymph node may not be detected because it may have integrated into the tumor. However, when they are detected, even if there are no obvious malignant findings, considering them metastatic regions and proceeding with treatment accordingly are necessary.