What are the other Names for this Condition? (Also known as/Synonyms)

• Benign Myoepithelial Tumour of Salivary Gland
• Myoepithelial Adenoma of Salivary Gland
• Salivary Gland Myoepithelioma

What is Myoepithelioma of Salivary Gland? (Definition/Background Information)

• Myoepithelioma of Salivary Gland is an uncommon benign tumor typically arising in the major salivary glands. It can be present in individuals of a wide age range (including children and adults)
• The cause of formation of Salivary Gland Myoepithelioma is not well-understood, although certain chromosomal alterations and gene mutations have been identified, based on the cases studied
• Most tumors are solitary, small, and painless, though the larger ones may compress the surrounding structures and cause related signs and symptoms. When the minor salivary glands are affected, the tumor may be noticed on the palate, lips, and tongue
• The diagnosis of Myoepithelioma of Salivary Gland can be confirmed through a tissue biopsy. The treatment is a complete surgical removal of the tumor with adequate margins
• The prognosis of Myoepithelioma of Salivary Gland is generally excellent with adequate treatment (complete removal through surgery). However, tumor recurrences are not uncommon, and some are even known to undergo malignant transformations

Who gets Myoepithelioma of Salivary Gland? (Age and Sex Distribution)

• Salivary Gland Myoepitheliomas constitute about 1.5% of all tumors affecting the salivary glands
• The tumor can be present in individuals of a wide age range (between 9-85 years) affecting adults and children
• A predilection for young and middle-aged adults is noted. Most cases are seen in the 20-30 years’ age group; the mean age of presentation is 44 years
• Both males and females are affected almost equally
• All races and ethnic groups may be affected

What are the Risk Factors for Myoepithelioma of Salivary Gland? (Predisposing Factors)

• No clearly identified risk factors for Myoepithelioma of Salivary Gland have been established to date

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Myoepithelioma of Salivary Gland? (Etiology)

• Currently, the cause of formation of Myoepithelioma of Salivary Gland is not definitely established
• However, based on cytogenic studies, myoepitheliomas have shown certain chromosomal changes and genetic defects
  • Around 25% of the tumors have shown mutations on gene TP53
  • Some abnormalities involving chromosomes 1, 9, 12, and 13 have been identified

What are the Signs and Symptoms of Myoepithelioma of Salivary Gland?

Myoepithelioma of Salivary Gland can affect both the minor and major salivary glands. The tumor constitutes approximately 5.7% and 2.2% of all benign tumors of the minor and major salivary glands respectively.

The signs and symptoms of Myoepithelioma of Salivary Gland may include:

• Presence of a tumor mass on the face or in the mouth; myoepitheliomas grow slowly and generally do not present any pain
• Most tumors arise in the major salivary glands; i.e., the parotid glands (in 40% of the cases). The submandibular glands may also be affected
• When the minor glands are involved, the tumor may be seen on the soft/hard palate, lips, inner cheek lining (buccal mucosa), floor of the mouth, gums, and even on the tongue
• Rarely, the tumors may be present in the respiratory tract
• The size may range from 10-35 mm, although some can grow to larger sizes
• The tumors are typically solitary, firm, and solid (spherical or oval)

Large tumors may cause the following signs and symptoms:

• Difficulty in opening one’s mouth; pain while eating (pain may be felt in the mouth and face)
• Numbness of part of the face
• Dryness of mouth
• Inability to move one side of the face due to damage to the facial nerve, known as facial nerve palsy
• Facial pain
• Breathing difficulty

How is Myoepithelioma of Salivary Gland Diagnosed?

The following exams and procedures may be used in the diagnosis of Myoepithelioma of Salivary Gland:

• Evaluation of the individual’s medical history and a through physical examination
• Plain X-ray of the head and neck region
• Ultrasound scan of the affected salivary gland
• CT or CAT scan with contrast of the head and neck usually shows a well-defined mass. This radiological procedure creates detailed 3-dimensional images of structures inside the scanned region
• MRI scans of head and neck region: A magnetic field is used to create high-quality pictures of certain parts of the body, such as tissues, muscles, nerves, and bones. These high-quality pictures may reveal the presence of the tumor

Although the above modalities can be used to make an initial diagnosis, a tissue biopsy of the tumor is necessary to make a definitive diagnosis to begin treatment. The tissue for diagnosis can be procured in multiple different ways which include: 

• Fine needle aspiration (FNA) biopsy of the tumor: A FNA biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a FNA biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy may be recommended.
• Salivary gland core biopsy of the tumor
• Salivary gland open biopsy of the tumor

Tissue biopsy:

• A tissue biopsy of the tumor is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis
• Biopsy specimens are studied initially using Hematoxylin and Eosin staining. The pathologist then decides on additional studies depending on the clinical situation
• Sometimes, the pathologist may perform special studies, which may include immunohistochemical stains, molecular testing, and very rarely, electron microscopic studies to assist in the diagnosis

A differential diagnosis, to eliminate the following tumor types are often considered, before arriving at a definitive diagnosis:

• Acinic cell carcinoma
• Clear cell carcinoma
• Epithelial-myoepithelial carcinoma
• Mesenchymal tumors (both benign and malignant)
• Mucoepidermoid carcinoma
• Oncocytoma
• Pleomorphic adenoma

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Myoepithelioma of Salivary Gland?

The following complications due to Myoepithelioma of Salivary Gland may be observed:

• Severe emotional stress and cosmetic concerns (facial disfigurement)
• Some tumors can be locally-infiltrative and destroy the surrounding tissue structures
• The tumors are known to recur following surgery to remove them
• Occasionally, recurrent and/or longstanding tumors are known to transform into malignancy (malignant myoepithelioma)
• Surgery to remove the tumor mass may result in facial nerve palsy (surgical complication)
• Post-surgical wound infection

How is Myoepithelioma of Salivary Gland Treated?

• A complete surgical excision with clear or wide margins is the preferred mode of treatment of Myoepithelioma of Salivary Gland
• Tumor recurrence may result in a need for multiple surgeries and more extensive therapies
• Radiation therapy may be administered when surgery is not a feasible treatment tool
• Post-operative care is important: One must maintain minimum activity levels, until the surgical wound heals
• Long-term follow-up may be required, because recurrence at the site of surgery have been reported many years (even decades) after surgery

How can Myoepithelioma of Salivary Gland be Prevented?

• Current medical research has not established a method of preventing the formation of Myoepithelioma of Salivary Glands
• Regular medical screening at periodic intervals with blood tests, radiological scans, and physical examinations, for those who have already endured the tumor, are helpful

What is the Prognosis of Myoepithelioma of Salivary Gland? (Outcomes/Resolutions)

• The prognosis of Myoepithelioma of Salivary Gland is generally excellent with surgical intervention and complete removal, since it is a benign tumor
• However, some tumors are known to recur. Besides recurrence, malignant transformations have been noted in rare cases. In such cases, the prognosis may depend upon the stage of the tumor, among other factors

Additional and Relevant Useful Information for Myoepithelioma of Salivary Gland:

There are 3 major types of salivary glands and these include the following:

• Parotid glands, found on the sides of the face
• Submandibular glands located at the back of mouth, on both sides of the jaw
• Sublingual glands that are seen under the floor of the mouth

The salivary glands produce saliva that helps in:

• Lubricating the mouth
• Swallowing
• Protects the teeth against bacteria
• Digestion of food