Extraaxial neurofibromas versus neurilemmomas: discrimination with MRI.
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.
Jee
Won-Hee
WH
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
Oh
Soon-Nam
SN
McCauley
Thomas
T
Ryu
Kyung-Nam
KN
Suh
Jin-Suck
JS
Lee
Jeong-Hoon
JH
Park
Jung-Mi
JM
Chun
Kyung-Ah
KA
Sung
Mi-Sook
MS
Kim
Kijun
K
Lee
Yeon-Soo
YS
Kang
Yong-Koo
YK
Ok
In-Young
IY
Kim
Jung-Man
JM
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