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CC BY 4.0 · J Brachial Plex Peripher Nerve Inj 2025; 20(01): e59-e65
DOI: 10.1055/a-2667-7286
Case Report

Ulnar Nerve Granuloma Presenting as a Peripheral Nerve Sheath Tumor: A Case Report and Literature Review

John K. Yue    *
1   Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States
,
Jia-Shu Chen   *
1   Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States
,
Mahmoud M. Elguindy   *
1   Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States
,
Vivian Tang
2   Department of Pathology, University of California, San Francisco, San Francisco, California, United States
,
Ryan Tripathy
3   Department of Neurological Surgery, University of California, Los Angeles, Los Angeles, California, United States
,
Allison R. Bond
4   Division of Infectious Diseases, Department of Medicine, University of California, San Francisco, San Francisco, California, United States
,
Alexander A. Aabedi
1   Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States
,
Vinil N. Shah
5   Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, United States
,
Arie Perry
1   Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States
2   Department of Pathology, University of California, San Francisco, San Francisco, California, United States
,
Andrew W. Bollen   **
2   Department of Pathology, University of California, San Francisco, San Francisco, California, United States
,
Dong Heun Lee   **
4   Division of Infectious Diseases, Department of Medicine, University of California, San Francisco, San Francisco, California, United States
,
Line G. Jacques   **
1   Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, United States
› Author Affiliations
Funding None.
› Further Information
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Abstract

Peripheral nerve masses have a wide differential diagnosis; however, there is no established diagnostic framework for evaluating non-neoplastic etiologies, such as inflammatory or infectious lesions. Here, we present a rare case of an ulnar nerve granuloma that initially mimicked a peripheral nerve sheath tumor (PNST) on imaging and clinical presentation to elucidate the relevant medical history, imaging, and histology that aid in distinguishing inflammatory, infectious, and neoplastic peripheral nerve lesions. An 85-year-old man with melanoma and multiple prior right elbow surgeries presented with right-hand weakness and a rapidly enlarging gadolinium-enhancing ulnar nerve mass suggestive of a PNST that warranted surgical resection. Surgical histology showed a necrotizing granulomatous lesion that then became most concerning for a parasitic infection. However, broad serum and histologic testing by the Centers for Disease Control and Prevention were all ultimately negative. The final diagnosis was an inflammatory reaction to a retained foreign body from his prior elbow surgeries. In summary, surgery and comprehensive histologic workup are required for diagnosing granulomatous peripheral nerve lesions that mimic PNSTs on imaging and infection on histology.

Keywords

foreign body reaction - granuloma - infection - peripheral nerve sheath tumor - ulnar nerve

Ethics

The patient provided written informed consent to include this clinical case in medical research and education publications. No protected health identifiers were included in the current report. The current report did not require review by an institutional review board because it is a case report and literature review and does not contain protected health identifiers.


* Co-first authorship.


** Co-senior authorship.




Publication History

Received: 28 June 2025

Accepted: 28 July 2025

Article published online:
19 August 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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