Myoepithelioma of the salivary glands

by Jason Wasserman MD PhD FRCPC
August 3, 2023

What is a myoepithelioma?

A myoepithelioma is a non-cancerous type of salivary gland tumour. It is made up of specialized myoepithelial cells that are normally found in the salivary gland. This tumour should not be confused with the similarly named myoepithelioma that starts in soft tissue.

Where is myoepithelioma normally found?

Most myoepitheliomas are found in the parotid gland although any of the other salivary glands including the submandibular gland, sublingual gland, and minor salivary glands in the oral cavity can be involved.

Is myoepithelioma a type of cancer?

No. Myoepithelioma is a benign (non-cancerous) type of tumour.

What causes a myoepithelioma?

At present, doctors do not know what causes myoepithelioma.

What are the symptoms of myoepithelioma?

The symptoms of myoepithelioma are typically a slow-growing, painless mass.

How is myoepithelioma diagnosed?

The diagnosis of myoepithelioma can be made after tissue from the tumour is examined under the microscope by a pathologist.

What does a myoepithelioma look like under the microscope?

When examined under the microscope, myoepithelioma is well-circumscribed (there is a clear border around the entire tumour), surrounded by a thin tumour capsule, and made up entirely of myoepithelial cells. The tumour cells may look spindled (long and thin), epithelioid (round and connected together), or plasmacytoid (similar to plasma cells). The stroma (connective tissue) surrounding the tumour cells may be described as myxoid, chondromyxoid, or fibrotic. The tumour cells usually show very little cytologic atypia and mitotic figures (cells dividing to create new cells) are rarely seen.

What other tests may be performed to confirm the diagnosis?

Immunohistochemistry

Immunohistochemistry (IHC) is a test that allows your pathologist to see markers such as proteins and other chemicals inside tumour cells. Cells that make (or express) a marker are called positive or reactive while those that do not make a marker are called negative or non-reactive. When immunohistochemistry is performed on a myoepithelioma, the tumour cells are usually positive for markers such as pan-cytokeratin, S100, SOX10, and GFAP.