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Ectomesenchymoma

Last updated Sept. 5, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Ectomesenchymoma is an infrequent, malignant ‘skeletal muscle’ tumor of the soft tissues with involvement of the nerves.


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

  • Gangliorhabdomyosarcoma
  • Malignant Ectomesenchymoma (MEM)
  • MEM (Malignant Ectomesenchymoma)

What is Ectomesenchymoma? (Definition/Background Information)

  • Ectomesenchymoma is an infrequent, malignant ‘skeletal muscle’ tumor of the soft tissues with involvement of the nerves. In other words, the tumor is described as a rhabdomyosarcoma (RMS, which is an aggressive malignancy) with neural involvement. Some researches indicate that Ectomesenchymoma may be a variant of RMS
  • The cause of tumor formation and specific risk factors that contribute towards the development of Ectomesenchymoma are unknown. However, the tumors are reported to have some similar genetic abnormalities to embryonal rhabdomyosarcoma
  • Ectomesenchymomas are poorly-defined, fleshy, expanding masses that form deep within the body tissues, or below the skin surface. A majority of the cases are observed in young children
  • The common location for this tumor is the abdominopelvic and head and neck region. The tumors are known to grow rapidly to large sizes and can severely affect the involved organs
  • The treatment of Ectomesenchymoma is undertaken through a combination of surgery, chemotherapy, and radiation therapy. The prognosis of Ectomesenchymoma depends on many factors including the stage of the cancer, size of the tumor, and response to therapy. In many cases, the prognosis is guarded

Who gets Ectomesenchymoma? (Age and Sex Distribution)

  • Ectomesenchymoma is a very rare tumor that is mostly observed in young children (including infants and neonates) below the age of 5 years
  • Over 80% of the cases are observed in children below age 15 years; although, 1 in 5 tumors are seen in adults
  • There is a slight predisposition towards males with a male-female ratio of 3:2
  • No specific racial or ethnic group preference is noted

What are the Risk Factors for Ectomesenchymoma? (Predisposing Factors)

  • Currently, no specific risk factors for Ectomesenchymoma have been reported

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 Ectomesenchymoma? (Etiology)

  • The cause of Ectomesenchymoma formation is believed to be due to genetic abnormalities
  • Various studies have revealed that Ectomesenchymoma show genetic features similar to embryonal rhabdomyosarcoma (a malignant tumor)
  • The tumor is believed to arise from embryonic connective tissues responsible for skeletal muscle development and embryonic nerve crest, since the tumor has a combination of muscle and nerve components

What are the Signs and Symptoms of Ectomesenchymoma?

The presentations are based on the location of Ectomesenchymoma. The signs and symptoms may include:

  • In the initial growing phase of the tumors, they are normally asymptomatic
  • The tumors are mostly fast-growing and infiltrative
  • They may be present on the skin at any location on the body, or located deep within the body tissues
  • The frequent sites of involvement include the abdomen, pelvis, and external genitalia (including the paratesticular tissues)
  • Other major sites for the tumor include the head and neck region; infrequent sites include the limbs
  • The size of the tumor may vary from 3 to 18 cm (with most tumors averaging about 5 cm at diagnosis)
  • As tumor grows rapidly, its presence is felt by pain and a sensation of mass. The mass can cause compression on the body region, resulting in obstruction of adjacent organs
  • Tumor necrosis and hemorrhage may be seen

How is Ectomesenchymoma Diagnosed?

Ectomesenchymoma is diagnosed by the following tests and procedures:

  • Complete physical examination and thorough evaluation of medical history
  • Ultrasonography of the affected region
  • CT, MRI scan of the affected region
  • Whole-body PET scan, bone scan of affected region to check for tumor metastasis. This helps with the staging 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

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 Ectomesenchymoma?

The complications from Ectomesenchymoma could include:

  • Complications are dependent on the site and stage of the tumor
  • Functional impairment of organs due to mass effect may occur from large-sized tumors
  • Metastasis of the tumor to local and distant regions
  • Tumor recurrence following surgery
  • Damage to vital nerves, blood vessels, and surrounding structures during surgery
  • Side effects from chemotherapy (such as toxicity), radiation therapy (radiation fibrosis)

How is Ectomesenchymoma Treated?

Treatment measures for Ectomesenchymoma is on similar lines of treatment for rhabdomyosarcoma and may include the following:

  • Wide surgical excision with removal of the entire lesion, which is followed by radiation and a course of intensive chemotherapy, is the standard treatment protocol
  • Advanced stage tumors with metastasis may be treated on a case-by-case basis; often, symptomatic treatment with radiation and/or chemotherapy is attempted
  • Arterial embolization of the tumor is used to provide temporary relief from the symptoms, and reduce blood loss during ‘tumor removal’ surgical procedure
  • Post-operative care is important: Minimum activity level is to be ensured until the surgical wound heals
  • Long-term follow-up care with regular screening and check-ups are important

How can Ectomesenchymoma be Prevented?

  • Current medical research has not established a method of preventing Ectomesenchymoma
  • Regular medical screening at periodic intervals with blood tests, scans, and physical examinations are mandatory for those who have already endured the tumor; due to its metastasizing potential and chances of recurrence. Often several years of active vigilance is necessary

What is the Prognosis of Ectomesenchymoma? (Outcomes/Resolutions)

  • The prognosis of Ectomesenchymoma depends on a combination of factors that include:
    • The size of the tumor and the extent of its invasion: Individuals with small-sized tumors fare better than those with large-sized tumors
    • Stage of cancer: 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 stage of the cancer is an independent prognostic factor
    • Cell growth rate of the cancer
    • 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 regional lymph nodes, 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. It is easier to treat the primary tumor; but, if metastasis occurs, treatment can be challenging
  • In general, the prognosis of Ectomesenchymoma is reported to be similar to rhabdomyosarcoma and is mostly guarded. The factors that favor positive outcomes include:
    • Lower stage of the tumor
    • Size of the tumor less than 10 cm
    • Tumors located on the skin (at superficial sites)
    • When the presence of other malignancies, such as alveolar rhabdomyosarcoma, is not noted

Additional and Relevant Useful Information for Ectomesenchymoma:

Amongst pediatric soft tissue sarcomas (affecting children less than 15 years), rhabdomyosarcomas form the largest category of malignancies.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: April 6, 2017
Last updated: Sept. 5, 2018