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A young adult man with neurofibromatosis type 1 (NF1) presented with a several-month history of an increasingly painful mass in the posteroinferior region of the right thigh. Imaging studies (Figure) showed a relatively well-circumscribed mass, 15 cm in length and 7 cm in diameter, arising on a background of very extensive involvement of the peripheral nervous system by plexiform neurofibromas. A biopsy specimen of the mass showed a high-grade (World Health Organization grade IV) malignant peripheral nerve sheath tumor (MPNST). An above-knee amputation was subsequently performed and the MPNST (Figure, inset A) was found to arise in continuity with one of the many preexisting low-grade (World Health Organization grade I) plexiform neurofibromas (Figure, inset B shows an example of such in the leg). For approximately 3.5 years following surgery and radiotherapy, there was no evidence of local tumor recurrence. The patient then was seen with a large left-sided retroperitoneal mass that was histopathologically confirmed to also be an MPNST, possibly a metastasis from the original thigh tumor but more likely a de novo primary tumor. He subsequently underwent several major debulking surgeries, radiotherapy, and rounds of chemotherapy, including palliative doxorubicin, for increasingly disseminated metastatic disease. He died approximately 7 years after his initial presentation.
Rossiter JP, Fenton PV. Malignant Peripheral Nerve Sheath Tumor in Neurofibromatosis Type 1. JAMA Neurol. 2014;71(2):242. doi:10.1001/jamaneurol.2013.2048