Differentiation of soft tissue benign and malignant peripheral nerve sheath tumors with magnetic resonance imaging.
OBJECTIVE
The objective of this study was to differentiate the magnetic resonance (MR) imaging appearance of benign peripheral nerve sheath tumors (PNSTs) from that of malignant PNSTs.


METHODS
Twenty-six patients who underwent MR imaging and had a histologic diagnosis of benign (schwannoma, n=16; neurofibroma, n=1) or malignant (n=9) PNST were retrospectively reviewed. The size, location, shape, margin, and signal intensities of the tumors on precontrast and gadolinium-enhanced MR imaging were analyzed. In each patient, the presence or absence of split fat, target, and fascicular signs was determined.


RESULTS
The mean size of the benign PNSTs (3.4 cm, S.D.=2.5 cm) was significantly smaller than that of the malignant tumors (8.2 cm, S.D.=3.1 cm) (P<.001). Seventeen (65.4%) of the 26 tumors were spindle shaped or ovoid (12 benign and 5 malignant tumors). Contiguity with specific nerves was identified in 15 (88.2%) of the 17 benign PNSTs but in none of the malignant tumors (P<.05). Well-defined margins were noted in all 17 benign PNSTs but in only 3 (33.3%) of the 9 malignant tumors (P<.001). Five (55.6%) of the 9 malignant PNSTs but none of the benign tumors showed signal intensity change in adjacent soft tissue (P<.05). There was no significant difference in signal intensity between the benign and malignant tumors on T(1)-weighted, T(2)-weighted, and contrast-enhanced MR images. The split fat and target signs were present more frequently in the benign PNSTs than in the malignant PNSTs (P<.05).


CONCLUSIONS
Benign and malignant PNSTs are often spindle shaped. Recognition of contiguity with adjacent nerves, a well-defined margin, and the presence of the split fat sign may suggest benignity. Imaging features suggestive of malignancy can be a larger size and an infiltrative margin.
Li
Chao-Shiang
CS
Department of Radiology, Taipei City Hospital-Renai Branch, Taipei, Taiwan, ROC.
Huang
Guo-Shu
GS
Wu
Hong-Da
HD
Chen
Wei-Tsung
WT
Shih
Li-Sun
LS
Lii
Jiunn-Ming
JM
Duh
Shyi-Jye
SJ
Chen
Ran-Chou
RC
Tu
Hsing-Yang
HY
Chan
Wing P
WP
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018317:Nerve Sheath Neoplasms / Q000175:diagnosis; D009442:Neurilemmoma / Q000175:diagnosis; D009455:Neurofibroma / Q000175:diagnosis; D010524:Peripheral Nervous System Neoplasms / Q000175:diagnosis*
D003287:Contrast Media; D019786:Gadolinium DTPA