Malignant peripheral nerve sheath tumor presenting in the cauda equina: diagnostic and biological pearls. Illustrative case

BACKGROUND Malignant peripheral nerve sheath tumors (MPNSTs) are rare and highly malignant tumors of neural crest origin. No matter their anatomical location, they are difficult to treat and carry a poor prognosis. OBSERVATIONS This report highlights the complexities of the diagnosis and management of a patient with MPNST of the cauda equina. The tumor retained the expression of H3K27me3, which is expected in spinal MPNSTs but uncommon in most sporadic and neurofibromatosis type 1–driven MPNSTs. LESSONS The described diagnostic nuance should be taken into consideration in patients with suspected MPNST of the cauda equina, as these tumors require swift neurosurgical intervention in order to maintain neurological function. Additional treatment modalities include neoadjuvant and adjuvant chemotherapy and radiotherapy. Although improvements in local control and progression-free survival have been reported, the role of radiation therapy and chemotherapy has been underinvestigated due to the rarity of MPNSTs presenting in this region.