Myoepithelioma of the soft palate: Review of the literature and report of a case with immunohistochemical study

Abstract

Myoepitheliomas of the salivary glands are rare neoplasms accounting for less than 1.5% of all salivary gland tumours. They are classified into four cell types: spindle, clear, epithelioid and plasmacytoid. The plasmacytoid cell type appears to have a predilection for the oral cavity, especially the palate. A 56-year-old man was admitted to the ENT department complaining of a painless soft palate mass that had shown progressive growth over the past 9 months. At oral examination, a firm, nodular, ovoid-shaped lesion measuring 2.5cm in diameter with a well-delimited border, was palpated at the posterior midline portion of the soft palate. The overlying mucosa was intact. Computed tomography (CT) showed a hypodense tumour image. The clinical picture was suggestive of a tumour of the small salivary glands. The patient underwent a complete surgical resection of the tumour. The latter was located in the submucosa. It consisted of polygonal cells with round, eccentric nuclei and eosinophilic cytoplasm. Focal necrosis was not observed. The mitotic index was 2/10 high-power fields. Immunohistochemically, the tumour cells showed positivity for S-100 protein, vimentin, GFAP and negativity for CK 14 and SMA. The immunoreactivity of Ki-67 was sporadic, confirming the diagnosis of benign myoepithelioma. Myoepithelioma composed predominantly of plasmacytoid myoepithelial cells is a rare neoplasm that occurs in the soft palate. Wide excision with tumour-free margins is the treatment of choice.