Malignant peripheral nerve sheath tumors: an update.

Malignant peripheral nerve sheath tumors (MPNSTs) are highly malignant cancers that account for approximately 5-10% of all soft tissue sarcomas. They occur either sporadically, in association with neurofibromatosis type 1 (NF1), or subsequent to radiation therapy. Histologically, MPNSTs resemble fibrosarcomas in their basic organization. Immunohistochemistry, particularly S100, plays an important role in the diagnosis. At the molecular level, loss of the NF1 gene and high levels of Ras-activity are hallmarks. Magnetic resonance imaging (MRI) is the most helpful imaging technique to clearly identify tumoral extent and to suggest neurogenic origin. The presence of heterogeneity with evidence of necrosis and hemorrhage on MRI and increased uptake on positron emission tomography scan may prove helpful in detecting malignant changes. MPNSTs need to be approached by a multidisciplinary team, assuring the complete surgical removal of the lesion. Disease-free and overall survival statistics reinforce the aggressive nature of this unique soft tissue tumor.