Adenosquamous carcinoma (ASC) is defined as a tumor showing components of adenocarcinoma with well-formed ductal structures and squamous cell carcinoma (SCC) in the same lesion. Only a few cases of oral ASC have been reported. The prognosis of ASC is generally poor. On the other hand, it has been demonstrated that the malignant transformation of oral leukoplakia is generally associated with pathological findings of well-differentiated SCC with low-grade malignancy. In this paper, we report a case of ASC on the tongue that developed during follow-up for leukoplakia. A 66-year-old woman visited our hospital with a chief complaint of a white painful tongue lesion in November 2009. At presentation, a white rough surface lesion measuring 18 × 8 mm was noted on the right margin of the tongue. The lesion was diagnosed to be oral leukoplakia on initial biopsy. After 3 years 10 months of observation, an erosive lesion was found at the same region. The lesion was diagnosed to be SCC on a second biopsy, and partial glossectomy was therefore performed. The surgical specimen revealed that growth and invasion of nuclear chromatin-rich atypical cells including Alcian-blue-positive mucous cells and partially recognized ductal structures. Finally, the lesion was diagnosed to be ASC (pT1N0M0). As of 4 years and 2 months postoperatively, the patient is doing well, with no evidence of recurrence.
