Myoepithelioma of the Parotid Gland: A Case Report and Literature Review.

Abstract

Tumors of the salivary glands are rare and have various histo-pathological subtypes. The overall incidence is 2.5-3 per 100,000 patients per year. Myoepithelioma of the parotid gland is very rare with an incidence of only 1-1.5% among all salivary gland tumors. The diagnostic criteria for benign myoepithelioma were laid down on the basis of the work of Barnes and Sciubba. A 30-year-old lady presented to our university with a mass slowly increasing in size. There were no aggravating and/or relieving factors found. On examination a 3 × 3cm diffuse swelling was found around the right pre auricular area. Fine Needle Aspiration Cytology (FNAC) was performed. The findings were suggestive of a pleomorphic adenoma. The patient underwent a right sided superficial parotidectomy to remove the tumor. The final histopathology report revealed the tumor to be a myoepithelioma. Myoepithelioma is a benign salivary gland neoplasm formed almost entirely of myoepithelial cells arranged in a sheet, island or cord-like fashion. On CT scans, it presents as a well-circumscribed homogenous lesion with lobulated or smooth margins. Myoepitheliomas may also have nodules that enhance under contrast and areas of linear bands that do not. The recommended treatment for a myoepithelioma is complete surgical excision with wide margins. It has a very low recurrence rate compared to the 15-18% recurrence rate for pleomorphic adenomas. Utilization of immunohistochemical staining is of utmost importance in suspected myoepithelioma cases to ensure proper treatment and follow-up. Myoepitheliomas are rare tumors which must be included in the differential if a patient presents with a tumor of characteristics similar to those described above. Immunohistochemistry and electron microscopy are useful tools for the diagnosis of myoepitheliomas.