title: Extraaxial neurofibromas versus neurilemmomas: discrimination with MRI.
abstract: OBJECTIVE
  The purpose of our study was to evaluate whether MRI can discriminate between extraaxial neurofibromas and neurilemmomas.
  
  
  METHODS
  MR images of 52 patients with a pathologically proven extraaxial neurofibroma or neurilemmoma were retrospectively reviewed by observers who were unaware of the surgical results, regarding the presence or absence of individual imaging criteria. MRI findings in 12 patients with a localized neurofibroma and 40 patients with a neurilemmoma were compared using the chi-square test or Fisher's exact test.
  
  
  RESULTS
  MRI findings suggestive of neurofibroma (p < 0.05) were a target sign on T2-weighted images (58% in neurofibromas vs 15% in neurilemmomas), central enhancement (75% vs 8%), and a combination of both findings (63% vs 3%). MRI findings suggestive of a neurilemmoma (p < 0.05) were a fascicular appearance on T2-weighted images (25% vs 63%), a thin hyperintense rim on T2-weighted images (8% vs 58%), a combination of both findings (8% vs 48%), and diffuse enhancement (13% vs 67%). No significant difference was seen between neurofibromas and neurilemmomas for a centrally entering and exiting nerve (42% in neurofibromas vs 23% in neurilemmomas), a peripherally entering and exiting nerve (58% vs 77%), a cystic area (38% vs 64%), a low-signal margin (100% vs 100%), peripheral enhancement (13% vs 26%), or a target sign on contrast-enhanced images (11% vs 31%).
  
  
  CONCLUSIONS
  MRI shows features helpful for differentiating extraaxial neurofibromas from neurilemmomas; however, no single finding or combination of findings allows definitive differentiation.
authors.affiliation: Department of Diagnostic Radiology, Kangnam St. Mary's Hospital, The Catholic University of Korea, 505 Banpodong, Seocho-gu, Seoul 137-701, South Korea. whjee@catholic.ac.kr
authors.forename: Won-Hee
authors.initials: WH
authors.lastname: Jee
authors.forename: Soon-Nam
authors.initials: SN
authors.lastname: Oh
authors.forename: Thomas
authors.initials: T
authors.lastname: McCauley
authors.forename: Kyung-Nam
authors.initials: KN
authors.lastname: Ryu
authors.forename: Jin-Suck
authors.initials: JS
authors.lastname: Suh
authors.forename: Jeong-Hoon
authors.initials: JH
authors.lastname: Lee
authors.forename: Jung-Mi
authors.initials: JM
authors.lastname: Park
authors.forename: Kyung-Ah
authors.initials: KA
authors.lastname: Chun
authors.forename: Mi-Sook
authors.initials: MS
authors.lastname: Sung
authors.forename: Kijun
authors.initials: K
authors.lastname: Kim
authors.forename: Yeon-Soo
authors.initials: YS
authors.lastname: Lee
authors.forename: Yong-Koo
authors.initials: YK
authors.lastname: Kang
authors.forename: In-Young
authors.initials: IY
authors.lastname: Ok
authors.forename: Jung-Man
authors.initials: JM
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000175:diagnosis*; D009455:Neurofibroma / Q000175:diagnosis*; D012189:Retrospective Studies