A schwannoma look-alike: solitary fibrous tumor of the cauda equina. Illustrative case.

backgroundSolitary fibrous tumors (SFTs) and schwannomas are two types of spinal neoplasms that pose significant challenges in differentiation when utilizing the preferred diagnostic modality for suspected spinal lesions, MRI. While schwannomas are generally subject to observation, particularly when presenting with asymptomatic or oligosymptomatic manifestation. SFTs require more immediate therapeutic intervention, due to their potentially aggressive characteristics and associated risk of patient harm if they are not thoroughly resected and addressed early. OBSERVATIONS: A 79-year-old patient was referred to the authors' clinic after receiving a diagnosis of schwannoma of the cauda equina 3 years earlier. Because of the oligosymptomatic presentation, the attending physician then implemented a watch-and-wait approach. A gross-total resection (GTR) was undertaken following progressive enlargement observed on successive MR images. The definitive pathological diagnosis revealed a grade 1 SFT. LESSONS: Spinal SFT should be regarded as a potentially aggressive neoplasm characterized by an invasive propensity toward adjacent structures as well as distal metastases. The adoption of conservative management for ambiguous lesions may increase the risk of an adverse outcome. Therefore, in the context of uncertain spinal lesions with inconclusive MRI findings, it may be advisable to proceed with GTR in conjunction with confirmation of the definitive pathological diagnosis. https://thejns.org/doi/10.3171/CASE2585.