Adenosquamous carcinoma development as a recurrence of squamous cell carcinoma in the oral floor: A case report.

Oral adenosquamous carcinoma (ASC) is rare and its origins are controversial. We here present a patient with oral ASC that developed after surgery for oral squamous cell carcinoma (SCC). A 70-year-old man with SCC on the oral floor underwent surgical resection. However, the enlarged ulcer presented on the oral floor 9 month after surgery. The biopsy of the ulcer revealed a SCC. Imaging examinations detected enhancement of a large lesion expanded to the tongue, but no evidence of regional lymph node or distant metastasis was shown. Based on these results, local recurrence of the cancer was diagnosed (cT4aN0M0). The surgery for the recurrent tumor was performed. The pathological examination of the surgical specimen indicated recurrent tumor was ASC. Thus, histopathological and immunohistochemical analyses of both the initial SCC and the subsequent ASC were performed in an attempt to explore the origin of the ASC. As the results, pathological review of both tumors suggested the subsequent ASC was developed from the tumor cells with adenoid phenotype in the initial SCC. This report suggests that the oral ASC was origin from the oral SCC, which can contribute to new knowledge for pathogenesis of oral cancer.