Diagnostic Quality of Magnetic Resonance Imaging Interpretation for Peripheral Nerve Sheath Tumors: Can Malignancy Be Determined?

Background Optimal management of peripheral nerve sheath tumors including neurofibromas, schwannomas, and malignant peripheral sheath tumors (MPNSTs) is predicated on knowing the specific pathology. Magnetic resonance imagining (MRI) has the potential to provide insight in the tumor type, yet imprecision in diagnosis remains. We assessed the accuracy of preoperative imaging diagnoses by comparing them with postoperative histopathologic diagnoses. We specifically focus on erroneous diagnosis of MPNSTs. Methods We reviewed all pathologically confirmed cases of nerve sheath tumors treated at our institution retrospectively from 2007 to 2015. Pre- and postoperative imaging data were reviewed for imaging-based diagnosis and compared with postresection pathologic diagnosis. Results The study included 127 patients: 82 diagnosed with neurofibroma, 17 with schwannoma, 24 with MPNST, and 4 with other histology types. A mean age of 40.8 ± 20.4 years, mean tumor size of 4.3 ± 3.6 cm, and mean follow-up of 29.1 ± 21.6 months were recorded. A family history of neurofibromatosis type 1 (NF1) was seen in 58 patients (46%). A discordant diagnosis from preoperative imaging and postoperative pathology was found in 65 individuals (51%). Most discordant diagnoses ( n  = 34) were inconclusive interpretation of preoperative imaging; however, 10 patients were diagnosed with a benign or unknown lesion on preoperative imaging but had an MPNST on histopathology. Patients with MPNST were more likely than those with benign pathologies to have larger lesions (7.6 ± 4.8 cm versus 3.5 ± 3.3 cm; p  = 0.004); however, a statistically acceptable threshold value could not be found to separate benign from malignant lesions. Clinical factors, such as NF1 status, did not meaningfully improve preoperative diagnosis. Conclusions These results suggest that routine MRI is insufficient to guide surgical decision making reliably. Additional imaging techniques may be necessary to delineate the radiologic features of nerve sheath tumors to determine pathology more precisely.