Malignant melanotic nerve sheath tumor mimicking a benign nerve sheath lesion: illustrative case.

BACKGROUND: Malignant melanotic nerve sheath tumors (MMNSTs) are rare neoplasms of Schwann cell origin that often arise along spinal nerves. They exhibit an estimated prevalence of 1% among primary peripheral nerve sheath tumors and carry an estimated mortality rate of 26%. This disease most commonly presents with localized pain and may also present with symptoms of cord compression. After radiographic imaging to identify suspected lesions, a definitive diagnosis is usually made through identification of PRKAR1A gene mutations. Typical management consists of tumor resection with adjuvant radiotherapy or chemotherapy, depending on case specifics. However, misdiagnosis due to tumor mimicking may slow correct diagnoses and subsequent treatment. OBSERVATIONS: The authors present a unique case of MMNST mimicking a benign nerve sheath lesion that resulted in neuropathy. Initial pathology reports identified the lesion to be of metastatic melanoma, but reexamination resulted in an ultimate diagnosis of MMNST. Rapid progression of the disease was observed. A subsequent review of the literature identified diagnostic considerations, treatment strategies, and avenues of research that may aid in diagnosis and treatment. LESSONS: MMNST should be considered when encountering suspicious peripheral nerve sheath lesions. Promptly performing appropriate biopsies and molecular testing is critical due to this condition's poor prognosis. https://thejns.org/doi/abs/10.3171/CASE25314.