Diagnostic challenges in a large palatal myoepithelioma filling the maxillary sinus and its classification as a tumour of uncertain malignant potential

Myoepithelial tumours of the salivary glands, including benign myoepithelioma and myoepithelial carcinoma, are rare tumours that account for <1% of all salivary gland tumours. We report a case of a 30-year-old male patient who presented with a complaint of a slow growing mass in the mouth for the past six months. Clinical examination revealed a single firm and tender swelling in left side of palate with an ulcerated surface. CT scan revealed a lesion infiltrating into the left side of the maxillary alveolus and extending into the maxillary sinus. Microscopically, diffuse sheets of spindle to ovoid shaped eosinophilic cells were noticed. Cellular atypia and mitotic figures were observed. Positive immunoreactivity was observed for vimentin and smooth muscle actin, along with a Ki-67 labelling index of 7%. Although the present case was diagnosed as a benign myoepithelioma, the presence of aggressive clinical and histopathological features prompted us to classify this tumour as a myoepithelioma with uncertain malignant potential.