Myoepithelioma is a rare salivary gland neoplasm. They most commonly affect the major and minor salivary glands with the parotid gland being the most common, approximately 40%. Only 1% of all salivary gland neoplasms are myoepitheliomas. Myoepithelioma is usually a benign tumor arising from neoplastic myoepithelial or basket cells which are found between the basement membrane and the basal plasma membrane of acinar cells. They also contain multiple cellular elements. We present a case of a 73-year-old female with myoepithelioma of the parotid gland, an extremely rare neoplasm. There have been approximately 42 cases reported through 1985 and fewer than 100 cases through 1993. We will discuss the clinical presentation, pathophysiology, diagnosis, and treatment of such neoplasms.
Of all benign major and minor salivary gland neoplasms, myoepitheliomas account for 2.2% and 5.7%, respectively. The parotid gland is affected in approximately 40% of cases. In total, myoepitheliomas only account for 1% of all salivary gland neoplasms. The overwhelming majority of myoepitheliomas are benign but malignant transformation can take place in recurrent cases and cases left untreated [
A 73-year-old female with a past medical history of hypertension, peripheral arterial disease, asthma, gastroesophageal reflux disease, and diabetes mellitus presented to our otolaryngology clinic with the complaint of a “nodule” behind her left ear. She stated that the mass had been slowly increasing in size over the last 5 years. It was described as nonpainful and she had never experienced any discharge from the area. Her only other complaints were decreased hearing, xerostomia, and hoarseness; no dysphagia or weight loss was reported. Past surgical history was significant for angioplasty and stent placement in her legs. Social history was significant for a 20-pack-year tobacco history. No significant family history was reported. On physical examination pertinent findings consisted of a left posterior auricular mass approximately 2 centimeters (cm) that was fixed and nontender. All cranial nerves, most notably the facial nerve, were intact. No cervical adenopathy was palpated. Nasopharyngeal laryngoscopy demonstrated arytenoid edema consistent with reflux but the true vocal folds were mobile and no other lesions were visualized. Treatment plan at that time consisted of smoking cessation and a computed tomography (CT) scan with contrast of the neck.
The CT scan revealed a multilobulated and cystic mass in the left parotid gland with an infiltrating appearance consistent with neoplasm. There was no pathologic cervical lymphadenopathy reported. The differential diagnosis at this time included benign mixed tumor, Warthin’s tumor, epidermoid tumor, and adenoid cystic carcinoma. A fine needle aspiration was performed at this time and the results were nondiagnostic. The decision was made to proceed with a left parotidectomy.
Left superficial parotidectomy with facial nerve monitoring was performed approximately one month after presentation. A
Hematoxylin and eosin, 40x, myoepithelial cells arranged in a fascicular nested pattern separated by collagen stroma.
Hematoxylin and eosin, 400x, Tumor showing an epithelioid pattern of uniform cells with central small nuclei with fine chromatin, inconspicuous nucleoli, and an eosinophilic cytoplasm. There is a mild degree of nuclear atypia without mitosis.
Immunohistochemical staining, 200x, calponin positivity
Immunohistochemical staining, 200x, CK5/6 positivity
Immunohistochemical staining, 200x, GFAP positivity
Immunohistochemical staining, 200x, p63 positivity
Immunohistochemical staining, 200x, S100 positivity
The patient recovered from the surgery without complications and her facial nerve was functioning well. The patient had no sign of recurrence at 10 months and is currently being seen regularly for routine monitoring.
The description of a salivary neoplasm resembling a myoepithelioma was first attempted in 1943 [
Myoepitheliomas only account for approximately 1% of all salivary neoplasms [
Of all benign major and minor salivary gland neoplasms, myoepitheliomas account for 2.2 and 5.7%, respectively. On gross inspection, they have a solid, tan or yellow-tan, glistening cut surface, similar to what was seen in our gross examination. Subtypes of myoepitheliomas are classified by cell morphology: spindle (interlacing fascicles with a stroma-like appearance), plasmacytoid/hyaline (polygonal cells with eccentric nuclei and dense, nongranular or hyaline, abundant eosinophilic cytoplasm), epithelioid (nests or cords of round to polygonal cells, with centrally located nuclei and a variable amount of eosinophilic cytoplasm), and clear (polygonal cells with abundant optically clear cytoplasm, containing large amounts of glycogen but missing mucin or fat) [
Most of these tumors occur in adults, with some cases reported in the pediatric population. Both genders are affected equally. The average age of a patient with myoepithelioma is 44 years, with a range of 9–85 years. The most common clinical presentation is a slow growing, painless mass, as seen in the clinical presentation of our patient [
The recurrence rate for myoepitheliomas has been reported to be 15–18%, with possible malignant transformation in long-standing tumors or recurring disease [
After complete surgical excision, routine follow-up is needed in the treatment algorithm of myoepitheliomas secondary to the recurrence rate. Currently in our patient there has not been any sign of recurrence. In conclusion, although myoepithelioma of the parotid gland is the most common site for a myoepithelioma to appear they are still a rare salivary gland neoplasm. It is challenging to obtain an exact number of cases that have been reported in the literature. However, it has been elucidated that there were 42 cases reported through 1985 and fewer than 100 cases through 1993 [
IRB waiver for case report was obtained from Mercy Fitzgerald Hospital in Darby, PA.
All authors of this manuscript have no financial disclosures or conflicts of interest.