Malignant Peripheral Nerve Sheath Tumors

Malignant peripheral nerve sheath tumors (MPNST) are uncommon, biologically aggressive soft tissue sarcomas of neural origin that pose tremendous challenges to effective therapy. In 50% of cases, they occur in the context of neurofibromatosis type I, characterized by loss of function mutations to the tumor suppressor neurofibromin; the remainder arise sporadically or following radiation therapy. Prognosis is generally poor, with high rates of relapse following multimodality therapy in early disease, low response rates to cytotoxic chemotherapy in advanced disease, and propensity for rapid disease progression and high mortality. The last few years have seen an explosion in data surrounding the potential molecular drivers and targets for therapy above and beyond neurofibromin loss. These data span multiple nodes at various levels of cellular control, including major signal transduction pathways, angiogenesis, apoptosis, mitosis, and epigenetics. These include classical cancer-driving genetic aberrations such as TP53 and phosphatase and tensin homolog (PTEN) loss of function, and upregulation of mitogen-activated protein kinase (MAPK) and (mechanistic) target of rapamycin (TOR) pathways, as well as less ubiquitous molecular abnormalities involving inhibitors of apoptosis proteins, aurora kinases, and the Wingless/int (Wnt) signaling pathway. We review the current understanding of MPNST biology, current best practices of management, and recent research developments in this disease, with a view to informing future advancements in patient care.