Objective: To assess the sensitivity and specificity of MRI criteria in the differentiation between malignant peripheral nerve sheath tumors (MPNST) and non-neurogenic malignant soft-tissue tumors (MSTT).
Design and patients: MRI examinations of 105 patients with pathologically proven malignant soft-tissue lesions (35 MPNST and 70 MSTT) were retrospectively reviewed, the reviewers being unaware of the pathological diagnosis. Using a standardized protocol, the tumors were evaluated for multiple parameters regarding morphology and appearance on different sequences before and after gadolinium contrast administration (location, distribution, delineation, homogeneity, size, shape, relationship to bone and neurovascular bundle, intralesional hemorrhage, necrosis, perilesional edema, lymphangitis and signal intensities). Results were compared using a chi-square or Fisher's exact test.
Results: MRI findings suggestive of MPNST (p<0,05) were intermuscular distribution, location on the course of a large nerve, nodular morphology, and overall non-homogeneity on T1-weighted images, T2-weighted images and T1-weighted images after gadolinium contrast injection. MRI findings in favor of MSTT were intramuscular distribution, ill-delineated appearance of more than 20% of the lesion's circumference, and presence of intralesional blood vessels, perilesional edema and lymphangitis. There is no significant difference for degree and pattern of enhancement after gadolinium contrast injection, nor for presence of bone involvement or cystic or necrotic areas.
Conclusion: MRI provides several features that contribute to the differentiation between MPNST and non-neurogenic malignant soft-tissue tumors. MRI findings suggestive of MPNST should be helpful to pathologists in the strategy for further examination.