Malignant Peripheral Nerve Sheath Tumor (MPNST) and Triton Tumor
Malignant peripheral nerve sheath tumors (MPNST) are tumors that arise from cellular components of a normal nerve, i.e., Schwann and perineurial cells, or from preexistent benign peripheral nerve sheath tumors (PNST). They are relatively uncommon and high
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Malignant Peripheral Nerve Sheath Tumor (MPNST) and Triton Tumor
Malignant peripheral nerve sheath tumors (MPNST) are tumors that arise from cellular components of a normal nerve, i.e., Schwann and perineurial cells, or from preexistent benign peripheral nerve sheath tumors (PNST). They are relatively uncommon and highly aggressive soft tissue tumors seen in three settings, sporadic, status postradiation, and associated with neurofibromatosis type 1 (NF1). Despite these different clinical scenarios, the biological background, loss of neurofibromin (NF1) expression by deletion or mutation, is believed to be similar. Beautifully conducted studies show common recurrent chromatin remodeling complex PRC2 inactivation through EED and SUZ12 mutations in a high proportion of all these MPNST clinical subsets, as a justification for examining epigenetic agents in MPNST [1, 2]. Older, abandoned terms for MPNST include neurofibrosarcoma, malignant schwannoma, and neurogenic sarcoma. It is recognized that epithelioid MPNST is not associated with NF1 and harbors different genetic signature than conventional MPNST, with often loss of tumor suppressor INI1, which may impact therapeutic options for this sarcoma subtype.
9.1 Presentation MPNST arises as a mass lesion that is often painful. Approximately one-third will be associated with NF1. Age distribution (Fig. 9.1) and site distribution (Fig. 9.2) for adult patients at MSKCC are shown. A different series described had a median age of 33 with a male predominance and a median size of 9.5 cm [3]. In NF1 patients, MPNST commonly arise in plexiform neurofibromas that undergo malignant transformation, typically in large nerves, such as the sciatic nerve, lumbosacral, or brachial plexus (Fig. 9.3). Remarkably, 10 % or fewer of patients with NF1 (also termed von Recklinghausen disease) will develop an MPNST. Conversely, other tumors are more common in NF1 patients, including
© Springer International Publishing Switzerland 2016 M.F. Brennan et al., Management of Soft Tissue Sarcoma, DOI 10.1007/978-3-319-41906-0_9
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Fig. 9.1 Age distribution of adult patients with malignant peripheral nerve sheath tumor. MSKCC 7/1/82–6/30/2010 n = 238
Fig. 9.2 Anatomic primary site distribution of adult patients with malignant peripheral nerve sheath tumor. MSKCC 7/1/82–6/30/2010 n = 238
Fig. 9.3 Gross pathology image of a sciatic nerve malignant peripheral nerve sheath tumor, highlighting the nerve entering and exiting the tumor
9.3 Diagnosis, Pathology
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benign dermal neurofibromas which are nearly universal, and plexiform neurofibromas, which occur in as many as half of NF1 patients, and optic gliomas (as many as 10–15 %) [4].
9.2 Imaging Imaging as for other primary high-grade sarcomas is predominantly MRI & CT, with one not preferred over the other (Figs. 9.4 and 9.5). That said, for tumors involving the brachial or lumbosacral plexus, MRI may have an advantage in outlining extent of tumor. The use of 18F-FDG PET scan to discern plexiform neurofibroma from MPNST is investi
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