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Low-grade malignant myoepithelioma arising in a pleomorphic adenoma: a rare case
Emad Raddaoui1, Ahmed S Al-Hujaily, Saleh F Al-Dhahri
1Department of Pathology, King Khalid University Hospital, Riyadh, Saudi Arabia. eraddaoui@yahoo.com
Abstract:
Malignant myoepithelioma is a very rare salivary gland tumor that can arise de novo or within a pre-existing pleomorphic adenoma. We report a case of malignant myoepithelioma most probably arising in a pre-existing pleomorphic adenoma of the left parotid gland. The patient was a 60-year-old man who presented with a multinodular mass lesion over left side of the face and neck. He had undergone removal of a pleomorphic adenoma of the left parotid gland twice (8 and 22 years ago). Histological examination showed locally concentrated highly invasive myoepithelial cells with bland-looking morphology and no evidence of mitosis or necrosis. Immunohistochemistry confirmed the myoepithelial differentiation (S- 100+, SMA+) and a low Ki-67 labeling index (<5%).
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