A case of squamous cell carcinoma of the floor of the mouth showing characteristics of adenosquamous carcinoma in a metastatic lesion.

Adenosquamous carcinoma is a malignant tumor initially described by Gerughty et al. in 1968. This tumor shows characteristics of both adenocarcinoma and squamous cell carcinoma and is extremely rare in the oral and maxillofacial region. We report a case of squamous cell carcinoma of the floor of the mouth showing characteristics of adenosquamous carcinoma in a metastatic lesion. The patient was a 45-year-old man, who consulted our department because of contact pain on the left side of the floor of the mouth. Examination of a biopsy specimen indicated a diagnosis of squamous cell carcinoma. The tumor was surgically removed after the patient had received preoperative arterial infusion chemotherapy with radiotherapy. Although there was no recurrence of the primary lesion, swelling of a submandibular lymph node was noted in the left side of the neck 6 months postoperatively. Therefore, total neck dissection was performed on the left side. Histopathological examination of the resected lymph node disclosed the presence of metastatic squamous cell carcinoma, which was intermixed with adenocarcinoma. The histopathological diagnosis was adenosquamous carcinoma. There were no other organs showing metastasis. However, the patient died of tumor recurrence 7 months later.