Major-nerve schwannomas versus intramuscular schwannomas.
BACKGROUND
A schwannoma is a benign peripheral nerve tumor. Predicting the involvement of a nerve on symptoms or magnetic resonance (MR) findings is crucial to the diagnostic process.


OBJECTIVE
To compare symptoms, MR findings, and histological findings between major-nerve schwannomas and intramuscular schwannomas.


METHODS
Thirty-four patients with 36 palpable schwannomas (29 major-nerve schwannomas and seven intramuscular schwannomas) surgically excised and proven histologically were retrospectively reviewed.


RESULTS
Frequencies of the Tinel-like sign, split-fat sign, entering and exiting nerve, and low-signal margin indicate the presence of a nerve, and were significantly higher in major-nerve schwannomas than in intramuscular schwannomas. In tumor morphological patterns (target sign, inhomogeneous and homogeneous pattern), there were no significant differences between major-nerve schwannomas and intramuscular schwannomas. Schwannomas showing the target sign histologically tended to be less degenerative. All major-nerve schwannomas and five of the intramuscular schwannomas produced some characteristic symptoms and/or MR findings, but two intramuscular schwannomas did not have any characteristic symptoms and findings.


CONCLUSIONS
In major-nerve schwannomas, the Tinel-like sign, split-fat sign, entering and exiting nerve, and low-signal margin are commonly observed and useful for diagnosis. In intramuscular schwannomas, these characteristic findings are less common, which makes diagnosis difficult.
Shimose
S
S
Department of Orthopedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan. shimose@hiroshima-u.ac.jp
Sugita
T
T
Kubo
T
T
Matsuo
T
T
Nobuto
H
H
Tanaka
K
K
Arihiro
K
K
Ochi
M
M
D000328:Adult; D000368:Aged; D001706:Biopsy / Q000379:methods; D003287:Contrast Media / Q000008:administration & dosage; D003937:Diagnosis, Differential; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D019042:Muscle Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D009442:Neurilemmoma / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D015588:Observer Variation; D010524:Peripheral Nervous System Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D011237:Predictive Value of Tests; D012189:Retrospective Studies
D003287:Contrast Media; D019786:Gadolinium DTPA