Intramuscular peripheral nerve sheath tumors: schwannoma, ancient schwannoma, and neurofibroma

  • Seul Ki Lee
  • Jee-Young KimEmail author
  • Yeon-Soo Lee
  • Hyang Sook Jeong
Scientific Article



To analyze the prevalence of classic magnetic resonance imaging (MRI) findings of intramuscular peripheral nerve sheath tumors (PNSTs), including schwannoma, ancient schwannoma, and neurofibroma.


Thirty pathologically confirmed benign intramuscular PNSTs (24 schwannomas, 3 ancient schwannomas, and 3 neurofibromas) were retrospectively reviewed. Classic MRI findings of PNSTs including split fat sign, fascicular sign, target sign, entering and exiting nerve, and thin hyperintense rim were assessed for each intramuscular PNST. Denervation change of the affected muscle was also assessed. In ancient schwannoma and neurofibroma, the signal intensity (SI) and enhancement pattern were analyzed.


All intramuscular schwannomas revealed two more classic MRI findings. Eight of the 24 intramuscular schwannomas revealed affected muscle denervation change. All intramuscular ancient schwannomas showed only split fat sign. All intramuscular ancient schwannomas showed denervation change of the associated muscle. All intramuscular neurofibroma showed split fat sign and one case with target sign was detected. Ancient schwannomas were isointense SI on T1-weighted image (T1WI) and one case had hyperintense foci. They showed heterogeneously hyperintense SI on T2-weighted image (T2WI) with heterogeneous enhancement. Neurofibromas were isointense SI (2/3) and slight hyperintense SI (1/3) on T1WI and heterogeneously hyperintense SI on T2WI with heterogeneous enhancement. One ancient schwannoma showed conglomerated calcifications.


Intramuscular schwannomas were easily diagnosed based on MRI. In the case of intramuscular ancient schwannoma and neurofibroma with only split fat sign among the classic MRI findings, they might be distinguished from other intramuscular soft tissue tumors based on muscle denervation change or typical crescent split fat sign.


Intramuscular peripheral nerve sheath tumor Split fat sign Fascicular pattern Target sign Thin hyperintense rim Entering and exiting nerves 


Compliance with ethical standards

Part of the population of this study (n = 18) originates from a previous study with different aim to determine the MRI findings for differentiating Intramuscular PNSTs [12]. No data have been fabricated or manipulated. No data, text, or theories by others are presented as if they were the author’s own. Proper acknowledgements to other works have been given, quotation marks were used for verbatim copying of material, and permissions were secured for material that is copyrighted. Authors whose names appear on the submission have contributed sufficiently to the scientific work and therefore share collective responsibility and accountability for the results. Authors are prepared to send documentation or data in order to verify the validity of their results.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval and informed consent

The institutional review board approved this retrospective study and the informed consent was waived.


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Copyright information

© ISS 2020

Authors and Affiliations

  • Seul Ki Lee
    • 1
  • Jee-Young Kim
    • 1
    Email author
  • Yeon-Soo Lee
    • 2
  • Hyang Sook Jeong
    • 3
  1. 1.Department of Radiology, College of MedicineSt. Vincent’s Hospital, The Catholic University of KoreaSeoulRepublic of Korea
  2. 2.Department of Radiology, College of MedicineDaejeon St. Mary’s Hospital, The Catholic University of KoreaSeoulRepublic of Korea
  3. 3.Department of Hospital Pathology, College of MedicineSt. Vincent’s Hospital, The Catholic University of KoreaGyeonggi-doRepublic of Korea

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