Nerve Tumors:What theMSK Radiologist Should Know

Nerve tumors are a subgroupof soft tissue tumors that are rare and heterogeneous.. Peripheral nerve sheath tumors (PNSTs) are defined as neoplasms arising from a peripheral nerve or showing nerve sheath differentiation. ►Table 1 lists pseudotumors and theWorldHealthOrganizationclassificationof the main PNSTs. They account for 12% of all benign and 8% of all malignant soft tissueneoplasms.2,3BenignPNSTsareprimarily composedof schwannomas and neurofibromas, each accounting for 5% of all benign soft tissue tumors, whereas malignant PNSTs account for 5 to 10% of all soft tissue sarcomas.3 It iswell knownthat inpatientswitha suspiciousdiagnosisof tumor, an early accurate diagnosis and appropriate treatment are crucial for a good outcome. Therefore, in a radiologic setting it is necessary to recognize soft tissue lesions with a neural origin, their associationwithaperipheralnerve, andwhether theyare a true tumor or a pseudotumor such as a neuroma, fibrolipoma, or peripheral nerve sheath ganglion. Imaging techniques such as ultrasound (US) andmagnetic resonance (MRI) imaging are the best modalities to characterize these lesions and have a direct impact on correct management and treatment of patients. In addition, US can be used to guide biopsy in difficult and uncertain cases when the lesion is either indeterminate or there is concern that the lesion is malignant.4 Following the guidelines regarding soft tissue tumors in adults approved by the European Society of Musculoskeletal Radiology (ESSR) for peripheral nerve tumors,4 biopsy could be avoided in cases of purely benign lesions. The proposed criteria include the following: