Spinal solitary fibrous tumor metastatic to the fourth ventricle: illustrative case.

backgroundCNS solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms that arise from the meninges and are characterized by a NAB2-STAT6 gene fusion and abundant STAT6 nuclear expression on immunohistochemistry. On imaging, SFTs can mimic meningiomas, but they differ in their clinical behavior. CNS SFTs have a propensity to recur locally and metastases, although rare, have been described. OBSERVATIONS: The authors report the case of a 76-year-old male with a history of a lower cervical spine SFT treated with surgery and radiation therapy. He presented with progressively worsening gait and balance, and headaches. Imaging showed a fourth ventricular mass that was resected via a midline suboccipital craniectomy. Pathological analysis showed a WHO grade 2 epithelioid SFT, confirmed by STAT6 expression and a rare NAB2ex5-STAT6ex17 fusion variant. The histology slides from 22 years prior were compared and found to be similar, suggesting metastasis of the original tumor. LESSONS: To the authors' knowledge, this is the first reported case of a spinal SFT with metastasis to the fourth ventricle and the first epithelioid SFT presenting within the fourth ventricle. Long-term follow-up is recommended due to the risk of local recurrence and metastases. https://thejns.org/doi/10.3171/CASE25414.