Target sign (peripheral nerve sheath tumor)

Last revised by Ayla Al Kabbani on 30 Mar 2021

The target sign of peripheral nerve sheath tumor (PNST) is a lesional pattern of T2 signal on MRI consisting of a central area of low intensity surrounded by a T2 hyperintense rim. It is most commonly associated with localized neurofibroma, having been shown to correspond histopathologically with a dense central area of collagenous stroma surrounded by myxomatous tissue 5.

Unfortunately, the target sign is neither sensitive nor specific for either neurofibroma or for benign tumor:

  • one study including 22 benign PNSTs showed a target sign in only 21% 4
  • a similar "target sign" has also been observed in schwannoma, albeit less commonly. It is believed that the histopathologic correlate may be the alternating Antoni A and B zones, the latter of which consist of tumor cells surrounded by edema-like fluid 1,2,5
  • a "target sign" has also been observed in malignant peripheral nerve sheath tumor 1,2,4

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Cases and figures

  • Case 1
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  • Case 2: peripheral nerve sheath tumor of the sciatic nerve
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  • Case 3
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