To describe clinical and radiological features of Malignant Peripheral Nerve Sheath Tumors (MPNSTs), both sporadic and neurofibromatosis type 1 (NF1)-associated forms; to identify findings that can help radiologists in the differentiation from Benign Peripheral Nerve Sheath Tumors (BPNSTs).

Tumors of peripheral nerve sheaths are divided into benign and malignant forms; the first group includes schwannomas and neurofibromas, the second one includes their malignant counterpart: malignant schwannoma, neurogenic sarcoma, neurofibrosarcoma; these terms are not now currently used and are replaced by the term MPNSTs (Table 1) [1]. MPNSTs represent about 3-10% of all sarcomas, in detail they include any sarcoma with at least one of the following features: -arising from a peripheral nerve -arising from a pre-existing benign nerve sheath tumor -demonstrating Schwann cell...

Various imaging techniques can be used for diagnosis of PNSTs. Ultrasonography is an easy and repeatable imaging modality, useful in superficial lesions but unsuitable for deep lesions [8]. CT allows evaluation of bone involvement, encasement of blood vessels and tumor staging. MRI, thanks to its high contrast resolution in characterization of different tissue properties, is considered the modality of choice in the study of PNSTs. Furthermore, due to the absence of radiation exposure and the possibility to identify features associated with malignant transformation, MRI can...

First of all, in the evaluation of PNSTs, radiologists should define the neurogenic origin of tumor; then, the combination of more signs of malignancy, together with clinical setting, can lead to diagnosis of MPNSTs. Heterogeneous signal on T2-weighted MR sequences and heterogeneous peripheral enhancement are the best imaging features that may be suitable for differential diagnosis from benign tumors. Comparison between radiological and histological examinations shows the strong agreement between radiological and morphological findings (Table 3).

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