title: MR imaging of extracranial nerve sheath tumors.
abstract: We retrospectively reviewed MR images of 32 histologically proven extracranial nerve sheath tumors (NSTs). There were 23 benign (10 neurofibromas, 13 schwannomas) and 9 malignant NSTs. On T1-weighted images (T1WIs) tumors were isointense or slightly hyperintense to muscle. On T2-weighted images (T2WIs) (11 lesions) and enhanced T1WIs (1 intraspinal lesion), a target pattern with peripheral hyperintense rim and central low intensity was seen in 12 of 23 (52%) benign NSTs (5 of 10 neurofibromas and 7 of 13 schwannomas). This pattern corresponded histologically to peripheral myxomatous tissue and central fibrocollagenous tissue. The pattern was absent in lesions with cystic, hemorrhagic, or necrotic degeneration. These tumors were hyperintense and variably inhomogenous on T2WIs. Malignant NSTs were hyperintense and variably inhomogenous on T2WIs and mimicked benign variably inhomogeneous lesions unless involvement of contiguous structures was visualized. A target pattern was not visible in malignant lesions. Magnetic resonance imaging cannot distinguish schwannomas from neurofibromas, and benign tumors may mimic malignant NSTs when cystic, hemorrhagic, and necrotic degeneration is present. A target pattern may be visualized in some benign NSTs, and evaluation of this sign with assessment of location and growth along nerves may help to avoid confusion with other lesions.
authors.affiliation: Department of Radiology, University of Texas M. D. Anderson Cancer Center, Houston 77030.
authors.forename: D G
authors.initials: DG
authors.lastname: Varma
authors.forename: A
authors.initials: A
authors.lastname: Moulopoulos
authors.forename: A S
authors.initials: AS
authors.lastname: Sara
authors.forename: N
authors.initials: N
authors.lastname: Leeds
authors.forename: R
authors.initials: R
authors.lastname: Kumar
authors.forename: E E
authors.initials: EE
authors.lastname: Kim
authors.forename: S
authors.initials: S
authors.lastname: Wallace
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009380:Neoplasms, Nerve Tissue / Q000175:diagnosis*; D009442:Neurilemmoma / Q000175:diagnosis*; D009455:Neurofibroma / Q000175:diagnosis*; D012189:Retrospective Studies