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

• MPNST (Malignant Peripheral Nerve Sheath Tumor)

What is Malignant Peripheral Nerve Sheath Tumor? (Definition/Background information)

• Malignant Peripheral Nerve Sheath Tumor (MPNST) is a type of soft tissue sarcoma (a malignant type of tumor). Approximately, 5% of soft tissue sarcomas are MPNSTs
• These tumors can occur in individuals with a history of neurofibromatosis type 1 (NF1, a genetic disorder affecting the skin and other body systems), or without NF1. About 65% of the individuals with MPSNT may be diagnosed with NF1
• There are 2 major types of Malignant Peripheral Nerve Sheath Tumor:
  • Spindled Malignant Peripheral Nerve Sheath Tumor (95% of the cases are of this type)
  • Epithelioid Malignant Peripheral Nerve Sheath Tumor (constitute about 5% of the cases)
• Malignant Peripheral Nerve Sheath Tumors typically occur in older adults, when there is no history of neurofibromatosis type 1. If it develops against a background of NF1, it usually occurs earlier
• The tumors are commonly present on the lower back, thigh, and upper arm. They are regarded as a kind of malignant cancer that spreads and infiltrates the surrounding tissues, tendons, muscles, and organs
• A combination of chemotherapy, radiation therapy, and surgical procedures, are used to treat Malignant Peripheral Nerve Sheath Tumors. The outcome for an individual with this tumor is guarded, due to its capacity to metastasize and recur

Who gets Malignant Peripheral Nerve Sheath Tumor? (Age and Sex Distribution)

• Malignant Peripheral Nerve Sheath Tumor not associated with neurofibromatosis type 1 usually occurs in individuals, who are in their 60s. Although, it can be present in a wider age range
• MPNST associated with NF1 are observed in individuals at a much younger age (less than 60 years)
• Males are affected more than females
• There is no known racial, ethnic, or geographical preference

What are the Risk Factors for Malignant Peripheral Nerve Sheath Tumor? (Predisposing Factors)

The risk factors for Malignant Peripheral Nerve Sheath Tumor include:

• The presence of neurofibromatosis type 1, a genetic condition that is characterized by skin pigmentation and the formation of non-cancerous tumors that affect the central nervous system
• A family history of MPNST

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 Malignant Peripheral Nerve Sheath Tumor? (Etiology)

• The exact cause and mechanism of formation of Malignant Peripheral Nerve Sheath Tumor is unknown
• They are thought to occur due to chromosomal defects occurring on account of certain genetic mutations
• Approximately 3-25% of neurofibromas can become malignant, resulting in MPNST

What are the Signs and Symptoms of Malignant Peripheral Nerve Sheath Tumor?

The signs and symptoms of Malignant Peripheral Nerve Sheath Tumor include:

• The presentations are generally based on the location of the tumor
• The tumor mostly occurs in the lower back, thigh, and upper arm. They may also occur in the head and neck region
• The tumors are usually over 5 cm in size and may be present as a mass
• In many individuals, loss of weight and appetite, and fatigue is observed. However, these symptoms appear later, as the cancer progresses

Additionally, there may be signs and symptoms of neurofibromatosis type 1, if present in the individual.

How is Malignant Peripheral Nerve Sheath Tumor Diagnosed?

A diagnosis of Malignant Peripheral Nerve Sheath Tumor may involve the following steps:

• Complete physical examination and comprehensive evaluation of individual’s medical history (including history of NF1)
• CT or MRI scan of the affected region to aid in obtaining a clear image of the tumor, prior to surgery
• Tissue biopsy: A tissue biopsy is performed and sent to a laboratory for a pathological examination, who examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist may arrive at a diagnosis
• Molecular analysis to exclude other tumors
• If tumor has metastasized (into the lungs or other regions) then PET scan, bone scan, and chest x-rays may be taken

Note: A tissue biopsy cannot help definitively diagnose a benign MPNST from a malignant MPNST. A tissue biopsy may show overlapping features between a malignant peripheral nerve sheath tumor and a benign peripheral nerve sheath tumor, when examined under a microscope by a pathologist. Clinical correlation as regards the behavior of the tumor is often necessary for a definitive diagnosis of malignancy.

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 Malignant Peripheral Nerve Sheath Tumor?

The complications of Malignant Peripheral Nerve Sheath Tumor may include:

• Metastasis of MPNST to the bones, lungs, or lymph nodes
• Damage of vital nerves, blood vessels, and surrounding structures, during surgery to remove the tumor
• Side effects from chemotherapy (toxicity), radiation therapy
• Recurrence of the tumor in case of incomplete excision and removal

How is Malignant Peripheral Nerve Sheath Tumor Treated?

The treatment of Malignant Peripheral Nerve Sheath Tumor may be undertaken as:

• Any combination of chemotherapy, radiation therapy, and invasive procedures may be used to treat MPNST
• Embolization is used to provide temporary relief from the symptoms, and reduce blood loss during a surgical procedure
• Wide surgical excision and removal of the entire tumor, followed by radiation therapy (or chemotherapy) is the standard treatment mode
• Post-operative care is important: One must maintain minimum activity levels, until the surgical wound heals
• Follow-up care with regular screening and check-ups are important and encouraged

How can Malignant Peripheral Nerve Sheath Tumor be Prevented?

• Current medical research have not established a way of preventing Malignant Peripheral Nerve Sheath Tumor
• Regular medical screening at periodic intervals with blood tests, scans, and physical examinations, are mandatory, due to its high metastasizing potential and possibility of recurrence. Often several years of active vigilance is necessary

What is the Prognosis of Malignant Peripheral Nerve Sheath Tumor? (Outcomes/Resolutions)

• The prognosis of Malignant Peripheral Nerve Sheath Tumor depends upon the stage of the tumor. In general, tumors occurring in the head and neck region are considered to be low-grade tumors, and hence, have the best prognosis
• The long-term outcome of MPNST may depend on several factors including the tumor size and location, age of the individual, the individual’s response to treatment, and if metastasis has occurred

Additional and Relevant Useful Information for Malignant Peripheral Nerve Sheath Tumor:

A differential diagnosis may be considered to eliminate the following conditions:

• Malignant melanoma
• Monophasic synovial sarcoma
• Fibrosarcoma