Squamous cell carcinoma of the buccal mucosa with multiple distant metastases

We report a rare case of squamous cell carcinoma (SCC) of the buccal mucosa with multiple distant metastases developing 6 months after resection. Because of its rarity and the multitude of organs involved by metastases, the treatment strategy was challenging and could not be standardized. A 61-year-old woman was referred to our institution in November 2016 for the diagnosis and treatment of a left buccal lesion. Biopsy revealed SCC. On the basis of the clinical diagnosis of buccal mucosal cancer (cT3N2bM0), intraoral tumor resection with neck dissection was performed. The postoperative course was uneventful. However, 6 months later, regional recurrence in the left nasopharyngeal mucosa occurred. Positron emission tomography/computed tomography revealed abnormal accumulations of fluorodeoxyglucose in the left lung, hilar lymph nodes, liver, adrenal glands, retroperitoneal lymph nodes, left clavicle, left scapula, ribs, thoracolumbar spine, sacrum, ilia, and femurs. Biopsy of the left ilium revealed SCC. These findings were compatible with multiple distant metastases from the oral SCC. To suppress the growth of distant metastases, platinum-fluorouracil chemotherapy plus cetuximab were administered, with responses in the nasopharynx and soft tissues only. Nivolumab was added to suppress the bone metastases; however, 7 days after administration, the patient died of acute respiratory distress syndrome. Evaluation of the expression of epithelial–mesenchymal transition markers including E-cadherin in the invasion front of oral SCC revealed normal results.