Imaging features and the role of image-guided biopsy for assessment of premalignant versus malignant peripheral nerve sheath tumors in neurofibromatosis type 1

Abstract Background To compare the magnetic resonance imaging (MRI) features of histologically proven premalignant peripheral nerve sheath tumors (PNSTs) with high-grade malignant PNST and explore the utility of core needle biopsy (CNB) for confirming the diagnosis in people with neurofibromatosis type 1 (NF1). Methods This study analyzed MRIs obtained from people with NF1 and histologically confirmed premalignant PNST (atypical neurofibromatous neoplasm of uncertain biologic potential [ANNUBP] or low-grade MPNST) or high-grade malignant PNST (MPNST). Demographic data, qualitative and quantitative imaging features (size and minimum apparent diffusion coefficient [ADCmin]), and diagnostic method (CNB or excision) were collected. Statistical analysis included Pearson’s chi-squared, Mann-Whitney U-tests, and Benjamini-Hochberg method. Results A total of 41 tumors in 40 patients (20 females [median age: 35, range: 14-66] with high-grade MPNST (n = 30) or premalignant PNSTs (n = 11)) were included. The presence of intralesional necrosis, perilesional edema, and perilesional enhancement (P < .05); greater T2 heterogeneity (P = .001); a higher largest and average diameter (P = .014 and P = .018, respectively); and a lower ADCmin (P < .001) were associated with high-grade MPNST. When applying a binary classification scheme of premalignant PNST versus high-grade MPNST, CNB offered the correct diagnosis in 93% (27/29) of the PNSTs. Conclusion The presence of intralesional necrosis, perilesional enhancement, and edema; higher T2 heterogeneity; large diameter (>10.5 cm) and average diameter (8.3 cm); and a lower ADCmin (<0.7 × 10−³ mm²/s) are associated with high-grade MPNST in people with NF1. As efforts continue to more precisely define transitional tumors molecularly, histologically, and clinically versus high-grade MPNST, these data contribute to the MRI diagnostic distinctions.