A Case of Myoepithelioma with Lipomatous Metaplasia of the Parotid Gland

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Myoepithelioma is a relatively rare form of salivary gland tumor, accounting for less than 1% of all salivary gland neoplasms. We herein report an extremely rare case of this tumor with lipomatous metaplasia of the parotid gland. A 50-year-old woman presented with a right-sided subauricular painless mass. Computed tomography, ultrasonography and magnetic resonance imaging demonstrated a 30×20mm well-defined ovoid tumor in the superficial lobe of the right parotid gland. A benign parotid tumor was clinically suspected, and she underwent superficial parotidectomy with preservation of the facial nerve. Histopathologically, the tumor consisted of spindle-shaped tumor cells arranged in solid and myxoid patterns containing abundant adipose tissue. Immunohistochemically, the tumor cells were positive for S-100 protein and α-smooth muscle actin. Based on these findings, the tumor was diagnosed as myoepithelioma with lipomatous metaplasia. The postoperative clinical course was uneventful, and the patient is currently free from disease 36 months after surgery. The pathology of myoepithelioma and a possible pathogenesis in the occurrence of adipocytes in this tumor are reviewed from the literature.