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Alveolar Soft Part Sarcoma (ASPS)

Diseases & Conditions
Cancer & Benign Tumors
Contributed byKrish Tangella MD, MBAApr 13, 2018

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

  • Granular Cell Myoblastoma
  • Malignant Granular Cell Myoblastoma
  • Malignant Myoblastoma

What is Alveolar Soft Part Sarcoma? (Definition/Background Information)

  • Alveolar Soft Part Sarcoma (ASPS) is an extremely infrequent, but highly malignant tumor of the soft tissues and muscles. It is formed due to chromosomal aberrations (chromosome 17 and X chromosome) causing abnormal fused genes. This abnormal gene forms a certain kind of protein that is responsible for the tumor formation
  • Young individuals are most prone to this disorder. Most of these tumors are well-defined and form deep within the body tissues, including in the muscles, nerves, and bones
  • The most common location for this tumor is the thigh, leg, and buttock. Other not so common locations include the head and neck (usually in children), female genitalia, and abdominal cavity
  • Treatment involves surgical removal of the tumor, followed by radiation therapy. However, even with proper management of the condition, the prognosis is generally grim

Who gets Alveolar Soft Part Sarcoma? (Age and Sex Distribution)

  • Alveolar Soft Part Sarcomas are mostly observed during an individual’s young adult phase (average ages: females 20 years, males 30 years). Children are also known to be affected
  • There is a slight predisposition towards the female sex (female to male ratio 3:2)
  • There is no known ethnic/racial preference

What are the Risk Factors for Alveolar Soft Part Sarcoma? (Predisposing Factors)

The risk of Alveolar Soft Part Sarcoma is linked to the following factor:

  • Genetic defects on chromosome 17 & X chromosome

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones 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 Alveolar Soft Part Sarcoma? (Etiology)

  • The exact cause and mechanism of Alveolar Soft Part Sarcoma formation, is unknown. The tumor is said to arise from embryonic connective tissues
  • They are thought to occur as a result of gene fusion. The fusion gene occurs when small pieces of two chromosomes break and join to form a new combination gene
  • Due to the creation of this new gene; a certain ‘new’ protein forms, previously not found in healthy cells. This protein is responsible for Alveolar Soft Part Sarcoma. However, the exact process of how the tumor develops due to this, is unclear

What are the Signs and Symptoms of Alveolar Soft Part Sarcoma?

The presentations are based on the location of Alveolar Soft Part Sarcoma. Signs and symptoms of Alveolar Soft Part Sarcoma include:

  • In the initial growing phase of the tumors, they are normally asymptomatic. This makes for difficult detection, until the metastasizing stage has occurred (in most cases)
  • The thigh and buttock (almost 40% of the time) is the primary location of Alveolar Soft Part Sarcoma
  • This is followed by the leg, head and neck (seen mostly in children), trunk, female genitals, breast, urinary bladder, and abdominal cavity. The tumors are mostly observed around tissues and muscles
  • Due to large size of tumor growth, the adjoining organs, nerves, and muscles may be compressed/restricted, impeding motion range. Often these signs due to compression, along with pain and tenderness, may be the first indications of the tumor
  • Functional impairment of organs are not observed until advanced stages of the tumor development takes place

How is Alveolar Soft Part Sarcoma Diagnosed?

The diagnosis of Alveolar Soft Part Sarcoma is difficult due to its unusual behavior and resemblance to many other tumors. ASPS is diagnosed by:

  • Physical examination with evaluation of patient’s medical history
  • Biopsy of tumor: Histopathological studies conducted on a biopsy specimen; a pathologist examines the tumor under a microscope
  • CT, MRI scan of the affected region
  • Bone scan
  • Blood test (total blood count)

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 Alveolar Soft Part Sarcoma?

The complications from Alveolar Soft Part Sarcoma could include:

  • Complications are dependent on the site and severity (stage) of the tumor. It is easier to treat the primary tumor. After metastasis occurs, treatment is generally challenging. Frequently metastasized regions include the lungs, brain, spinal cord, and bones
  • Usually by the time ASPSs are detected, chances are that they would have proliferated and metastasized aggressively (damaging organs and tissues beyond reasonable repair)
  • This kind of sarcoma is known to having a high recurrence rate (between 11-50%), even after surgical excision and removal
  • Damage to vital nerves, blood vessels, and surrounding structures during surgery

How is Alveolar Soft Part Sarcoma Treated?

  • Any combination of chemotherapy, radiation therapy, and invasive surgical procedures are used to treat Alveolar Soft Part Sarcoma. Though chemotherapy (either oral drugs, or intravenous administration) is usually not very effective
  • Arterial embolization of the tumor is used to provide temporary relief from the symptoms, and reduce blood loss during a surgical procedure
  • Wide surgical excision of ASPS with removal of the entire lesion is the standard treatment mode. This is followed by radiation therapy. If the tumor is not fully removed, then it might recur after many years
  • Non-invasive procedures are adopted, when ASPS is at an inaccessible location, or is unsafe for surgical intervention
  • Post-operative care is important: Minimum activity level is to be ensured until the surgical wound heals. Follow-up care with regular screening and check-ups are important

How can Alveolar Soft Part Sarcoma be Prevented?

  • Current medical research have not established a way of preventing Alveolar Soft Part Sarcoma
  • Genetic counseling and testing may help
  • The presence of any tumor or lesion should be immediately informed to the physician and periodic follow-up screening maintained
  • Regular medical screening at periodic intervals with blood tests, scans and physical examinations are mandatory for those who have already endured ASPS. This is due to both its high metastasizing potential and chances of recurrence. Often several years of active vigilance is necessary

What is the Prognosis of Alveolar Soft Part Sarcoma? (Outcomes/Resolutions)

  • Alveolar Soft Part Sarcomas are rare, but highly malignant cancers that are not completely understood
  • The long-term prognosis depends on a combination of factors such as; age of the individual, tumor stage at detection, size, type, and location of the tumor, Ki-67 index (a protein found in cells that is a good indicator of cell activity), its response to treatment & medical therapy, and whether it has spread around the area, or to other distant locations
  • The long-term outcome is poor for most individuals (45-85% mortality over a 5 year period); unless they are young children
  • There is a long gap (sometimes 5-6 years) between the primary excision surgery and appearance of secondary metastasized tumors. Once this occurs, then managing the condition is very difficult; at this phase the tumor is also resistant to regular chemotherapy medicines

Additional and Relevant Useful Information for Alveolar Soft Part Sarcoma:

The gene responsible for the high metastasizing capabilities of ASPS has been identified recently, and is being studied. It is hoped that certain targeted medical therapies can be developed based on these new findings.

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Krish Tangella MD, MBA

Pathology, Medical Editorial Board, DoveMed Team


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