Myoepithelial carcinomas, also known as malignant myoepitheliomas, are rare malignant salivary gland tumors. Myoepithelial carcinoma makes up <2% of all salivary gland malignancies 1,3.
On this page:
Epidemiology
Myoepithelial carcinoma affects males and females at an equal rate. The mean age at presentation is 55 years 2.
Clinical presentation
The vast majority of myoepithelial tumors originate in the parotid gland and are locally destructive 3. Local invasion can lead to perineural or angiolymphatic invasion. Symptoms of local parotid involvement include:
painless enlarging mass at the parotid that is non-ulcerating
painful, ulcerative masses can occur but are less common
facial paralysis and/or paresthesia
Pathology
In up to 75% of cases, these affect the parotid gland but can also arise in the submandibular and minor salivary glands. They may arise de novo or from a pre-existing myoepithelioma or pleomorphic adenoma 4. Myoepithelial carcinoma can arise within non-salivary soft tissues and bones.
Macroscopic features
On gross pathology, myoepithelial carcinomas typically appear as unencapsulated with nodular surfaces and are white in appearance. They can vary in size from 2-10 cm at presentation but on average are 3.5 cm.
Microscopic features
Similar to its benign analog, myoepithelioma, a range of cell types within myoepithelial carcinoma may be present including clear, spindled, epithelioid, and plasmacytoid cells. Tumors may have a mix of cell types. Cells have myoepithelial differentiation1. The overall tumor has a multilobulated architecture and may have areas of cystic degeneration or necrosis. Tumor stroma is hyaline or myxoid3.
Radiographic features
The imaging appearance can vary depending on tumor grade. Myoepithelial carcinomas typically are lobulated or multinodular lesions with ill-defined borders. Myoepithelial carcinomas have inhomogeneous density and can have cystic-appearing regions present. Tumors may be unencapsulated or have an incomplete capsule 4.
CT
On contrast-enhanced CT imaging, small tortuous vessels may be seen in the arterial phase. Hyperenhancement is commonly seen. In the venous phase, cystic and slit-like regions without enhancement are more evident 4,5.
Treatment and prognosis
Surgical resection for isolated disease is typically performed. Radiation therapy may be utilized. Neck dissection and adjuvant radiotherapy for cases with metastasis can be utilized 3. The overall prognosis is poor. The reported disease-related death rate ~20% (range 13-30%); another 30% of patients will experience recurrence of disease after resection, and one-third will develop distant metastasis 3,6.
Differential diagnosis
Considering the variability in appearance, the imaging differential can vary. The differential includes a number of malignant salivary gland tumors based on appearance. In addition to the more common salivary gland malignancies, other tumors to consider in the differential include:
epithelial-myoepithelial carcinoma
Unable to process the form. Check for errors and try again.