Malignant tumors of the minor salivary glands are very rare and most cases occur in the oral cavity, e.g., the palate, tongue, cheek and lip. We report herein on an extremely rare case of carcinoma ex pleomorphic adenoma arising in the fossa of Rosenmuller. An 83-year-old man, who had consulted another clinic with a complaint of hemosputum, was referred to our hospital because of the presence of a nasopharyngeal tumor. The tumor was resected via a transnasal endoscopic procedure without any major complications. The tumor was found to have arisen in the fossa of Rosenmuller and extended to superior lateral side behind the Eustachian tube cartilage. Histological examination showed that the main part of the tumor consisted of a pleomorphic adenoma, however, capsular invasion, nuclear atypia and mitosis were observed in a limited area where the MIB-1 index was high. We diagnosed the lesion as a carcinoma ex pleomorphic adenoma. We did not perform any postoperative therapy, because the area containing malignancy was far from the surgical margin and the patient was rather elderly. Three years and 10 months after the surgery, he remains in follow-up and has not shown any recurrence of the tumor.
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