Myoepithelial carcinoma arising in a pleomorphic adenoma of the parotid gland: Report of a case with cytopathologic findings

Background Carcinoma arising in a, mixed tumor, or carcinoma ex pleomorphic adenoma (CEPA), is an uncommon primary salivary gland neoplasm. Among the various types of carcinomas that, can be seen histologically in a CEPA, myoepithelial carcinoma is one of the rarest forms. Case A 76-year-old woman presented with an incidental parotid/parapharyngeal mass. Computed tomography-guided fine needle aspiration (FNA) showed a biphasic neoplasm with epithelial and stromal components consistent with pleomorphic adenoma (PA). However, in addition, a distinct population of discohesive atypical and pleomorphic cells with high nuclear/cytoplasmic ratio was noted in the background. In the cytopathologic diagnosis a suspicion was raised about a possible CEPA. Subsequent resection of the parotid mass confirmed the presence of low grade myoepithelial carcinoma arising in a PA. Conclusion Although uncommon, CEPA should be suspected on FNA when atypical cytomorphologic characteristics are observed. In rare cases a myoepithelial carcinoma also arises in a pre-existing PA, necessitating an accurate interpretation for more definitive therapy.