A case of myoepithelial carcinoma ex pleomorphic adenoma of the parotid gland

Background : Carcinoma ex pleomorphic adenoma (CXPA) is a malignancy developing from primary pleomorphic adenoma (PA). It is rare to see both benign and malignant components of CXPA in cytology specimens. We report a case of myoepithelial carcinoma ex pleomorphic adenoma, in which both benign and malignant components were detected in the cytology specimens.Case : A woman in her nineties presented to us with a submucosal mass on the right palate that she had had for 13 years. She had been followed up as a case of benign tumor. However, in the previous seven months, the mass had enlarged rapidly. Fine needle aspiration cytology was performed to determine the appropriate treatment strategy. Cytological examination revealed weakly cohesive clusters of large atypical cells, consistent with the features of carcinoma cells. Histologic examination of the resected tumor showed tumor nests composed of polygonal cells with enlarged irregular nuclei. Based on the histologic and immunostaining results, the tumor was diagnosed as a myoepithelial carcinoma. In addition, PA components were also identified in the tumor tissue, based on which we made the diagnosis of CXPA. A review of the cytological finding after the histological diagnosis revealed the PA components.Conclusion : In a case with a clinical course suggestive of CXPA, cytological observation should be performed bearing in mind the possibility of finding both PA and carcinoma components.