American Society for Peripheral Nerve

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A Clinical and Radiographic Score to Assess Malignant Potential in Peripheral Nerve Sheath Tumors
Christopher J Winfree, MD; Jonathan P Yun, MD
Columbia University, New York, NY

Introduction: The differentiation of malignant peripheral nerve sheath tumors (MPNST) from benign nerve sheath tumors is critical, as the treatments of these two lesions differs drastically. While histopathological diagnosis remains the gold standard, clinical and radiographic assessments are key for lesions that present with diagnostic uncertainty, such as benign appearing lesions with progressive neurologic symptoms. Previous studies have attempted to distinguish lesions based on these criteria but have been limited by low sensitivity and specificity. Here, we describe scoring system based on clinical presentation, neurological examination, and contrast enhanced MRI and apply it retrospectively to a single surgeon series of peripheral nerve sheath tumors.

Methods: Clinical characteristics common to the presentation of patients with peripheral nerve sheath tumors were identified by the surgeon, which includes pain, neurologic deficits, schwannomatosis, and entrapment. Further, salient imaging characteristics, such as contrast enhancement, tissue edema, and border irregularity were noted. The degree of the presenting characteristic was assigned a score of -1 or +1, whether it suggested for or against malignancy, respectively, and with 0 assigned for an absence of the characteristic. This scoring system was retrospectively assigned to peripheral nerve sheath lesions diagnosed from 2004-2015 and treated by the senior author. All patients have had pathologic studies. Statistics were performed with two-tailed t-test and ROC analysis.

Results: A total of 50 nerve sheath tumors were identified, of which 8 were MPNST. The average malignancy score of benign lesions were 0.1(range -1 to 1, sd=0.58) was significantly different from the average score of MPNST were 4.38(range 3 to 5, sd=0.58) (p<0.0001). Furthermore, a ROC analysis reveals an AUC of 1.0, with a score of >2 having 100% sensitivity and specificity for malignancy.

Conclusions: Obtaining histopathologic diagnosis is critical for the diagnosis of MPNST, however the decision to operate may be difficult in cases with features suggestive of both benign and malignant pathologies. A score that can be quickly calculated based on clinical charateristics and radiographic imaging, with adequate sensitivity and specificity, is a valuable tool during the initial consultation with these patients. We demonstrate an example of such a scoring criteria, though prospective validation with multiple surgeons and patients would be required.

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