“Malignant Pleomorphic Adenoma” in the Palate

Abstract

A case of tumor occurring in the palate of a 74-year-old Japanese female is reported. Although histological and immunohistochemical features of the tumor were identical to those of pleomorphic adenoma, except for scarce pleomorphic or “mixed” appearance, diffuse cellular and nuclear pleomorphism and relatively high proliferative cellular activity were observed. However, there was no metastasis or recurrence, indicative of its low-grade malignancy. Preexisting benign pleomorphic adenoma was not recognized. Due to these characteristics, we consider that the tumor should be diagnosed as “malignant pleomorphic adenoma” or “lowgrade malignant mixed tumor” and propose to separate such types of tumor from ordinary types of pleomorphic adenoma and carcinoma in pleomorphic adenoma.