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

• Malignant Myoepithelial Tumour
• Malignant Myoepithelioma
• Myoepithelial Cancer

What is Myoepithelial Carcinoma? (Definition/Background Information)

• Myoepithelial Carcinoma is an uncommon, malignant, soft tissue tumor of myoepithelial cells. It is similar to salivary gland myoepithelial tumors showing same histological features (morphology). It is also known as a Malignant Myoepithelial Tumor
• It can be present in individuals of a wide age range, though many tumors are found in children. The risk factors for Myoepithelial Carcinoma are not well-understood
• The cause of formation of Myoepithelial Carcinoma is reported to be due to certain chromosomal alterations and gene mutations. The involvement of EWSR1 gene is observed in about 45% of the myoepithelial tumors
• Most tumors are solitary and small, though the larger ones may compress the surrounding structures and cause related signs and symptoms. Most myoepitheliomas are found on the limbs (arms and legs)
• The diagnosis of Myoepithelial Carcinoma can be confirmed through a tissue biopsy. The treatment is a complete surgical removal of the tumor with adequate margins. This may be followed by additional therapies including radiation therapy and chemotherapy
• The prognosis of Myoepithelial Carcinoma is based on several factors including the stage of the tumor, but is generally guarded. Also, tumor recurrences are not uncommon

Who gets Myoepithelial Carcinoma? (Age and Sex Distribution)

• Myoepitheliomas can be present in individuals of a wide age range. However, a predilection for young and middle-aged adults is noted (median age 40 years)
• Many cases of Myoepithelial Carcinomas are reported in children
• Both males and females are affected
• All races and ethnic groups may be affected

What are the Risk Factors for Myoepithelial Carcinoma? (Predisposing Factors)

• No clearly identified risk factors for Myoepithelial Carcinoma 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 Myoepithelial Carcinoma? (Etiology)

The cause of formation of Myoepithelial Carcinoma is due to genetic mutations and the following are noted:

• Mutation on EWSR1 gene is observed in extra-salivary gland myoepithelial tumors (in about half of the cases)
• Fusion of EWSR1 gene with either POU5F1 or PBX1 gene seen in over 15% of the myoepithelial tumors
• Infrequently, EWSR1-ZNF444 fused gene is known to display chromosomal translocation t(19;22)(q13;q12); this translocation is also linked to abnormalities in the FUS gene
• In young adults/older children - deep soft tissue tumors on limbs have reported a fusion of EWSR1 and POU5F1 genes
• Other chromosomal aberrations noted include t(1;22)(q23;q12), t(6;22)(p21;q12) and rearrangement of 16p11.2
• Some tumors show abnormalities in the SMARCB1 gene

What are the Signs and Symptoms of Myoepithelial Carcinoma?

The signs and symptoms of Myoepithelial Carcinoma may include:

• Myoepitheliomas grow slowly and generally do not present any pain, during the initial stages
• In many, the presence of a tumor mass that may be felt/touched is observed
• The tumors appear as fleshy or firm nodules
• Tumors may be small or large with size ranging from 10 mm to 20 cm; average size varies from 4-6 cm
• The tumors are known to infiltrate the surrounding tissues
• 75% of the myoepithelial tumors involve the arms and legs (legs more than arms), including the armpits (shoulder girdle) and groin (pelvic girdle)
• Infrequently, chest, back, abdomen, and head and neck region may be involved
• Tumors have, even rarely, been observed in the internal organs and bones
• A significant subset of the tumors is seen on the skin (superficial myoepithelioma)
• Tumors below skin (subcutaneous myoepitheliomas) are more often noted, than tumors deep in the body affecting the organs/deep soft tissues

How is Myoepithelial Carcinoma Diagnosed?

The following exams and procedures may be used in the diagnosis of Myoepithelial Carcinoma:

• Evaluation of the individual’s medical history and a through physical examination
• Imaging studies including plain X-ray and ultrasound scan of the affected region
• CT or CAT scan with contrast of the affected region may show a 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.
• Core biopsy of the tumor
• 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

Diagnostic criteria for Myoepithelial Carcinoma (on examination under a microscope):

• The presence of atypical features: Moderate or severe nuclear atypia is a reliable and possibly the most important trait for malignancy
• High cell division rate
• Tumor necrosis
• Tumors in children contain undifferentiated round cell component

Note: A differential diagnosis is often considered before arriving at a definitive diagnosis.

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 Myoepithelial Carcinoma?

The following complications due to Myoepithelial Carcinoma may be observed:

• Severe emotional stress and cosmetic concerns (if the tumors are superficially located, or are present in the head and neck region)
• The tumors can be locally-infiltrative and destroy the surrounding tissue structures
• Deep-seated tumors may adversely affect the function of the organs
• The tumors are known to recur following surgery to remove them
• Advanced stage tumors can metastasize to the lungs, bone, lymph nodes, and other soft tissues
• Surgical complications and post-surgical wound infections

How is Myoepithelial Carcinoma Treated?

• A complete surgical excision with clear or wide margins is the preferred mode of treatment of Myoepithelial Carcinoma
• Tumor recurrence may result in a need for multiple surgeries and/or more extensive therapies
• Additionally, chemotherapy and radiation therapy may be administered. This may also be undertaken, 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 after surgery

How can Myoepithelial Carcinoma be Prevented?

• Current medical research has not established a method of preventing the formation of Myoepithelial Carcinoma
• 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 Myoepithelial Carcinoma? (Outcomes/Resolutions)

• The prognosis for Myoepithelial Carcinoma is generally guarded. Due to its extreme rarity, accurate prognostic parameters/values are not currently available. However, about 40-50% of the tumors are reported to recur or metastasize
• The prognosis, in general, depends upon a set of several factors that include:
  • Stage of tumor: With lower-stage tumors, when the tumor is confined to site of origin, the prognosis is usually excellent with appropriate therapy. In higher-stage tumors, such as tumors with metastasis, the prognosis is poor
  • The size of the tumor: Individuals with small-sized tumors fare better than those with large-sized tumors
  • Overall health of the individual: Individuals with overall excellent health have better prognosis compared with those with poor health
  • Age of the individual: Older individuals generally have poorer prognosis than younger individuals
  • Individuals with bulky disease have a poorer prognosis
  • Involvement of the lymph node, which can adversely affect the prognosis
  • Involvement of vital organs may complicate the condition
  • The surgical respectability of the tumor (meaning, if the tumor can be removed completely)
  • Whether the tumor is occurring for the first time, or is a recurrent tumor. Recurring tumors have worse prognosis compared to tumors that do not recur
  • Response to treatment: Tumors that respond to treatment have better prognosis compared to tumors that do not respond to treatment
  • Progression of the condition makes the outcome worse
• An early diagnosis and prompt treatment of the tumor generally yields better outcomes than a late diagnosis and delayed treatment

Additional and Relevant Useful Information for Myoepithelial Carcinoma:

• 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 following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/myoepithelioma-salivary-gland/