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

Background: Carcicoma 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 histologicatty in a CEPA, myoepithelial carcinoma is one of the rarest forms. Case: A 76-year-old -woman presented with an incidental parotid/parapbaryngeal mass. Computed tomography-guided fine needle aspiration (FNA) showed a bipbasic 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 cytopathokgic 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 cytomorphohgic characteristics are observed. In rare cases a myoepithelial carcinoma also arises in a preexisting PA, necessitating an accurate interpretation for more definitive therapy.