First reported case of intradural extramedullary epithelioid hemangioma of the cauda equina: resection of an extremely rare vascular neoplasm. Illustrative case

BACKGROUND Intradural extramedullary (IDEM) tumors of the cauda equina are most often meningiomas, nerve sheath tumors, and myxopapillary ependymomas; purely vascular IDEM lesions are exceptionally rare. Fewer than 30 IDEM hemangiomas have been reported, mostly cavernous or capillary. Epithelioid hemangioma (EH), a benign vascular neoplasm arising in soft tissue and bone, has not previously been reported at the cauda equina. OBSERVATIONS A 63-year-old male with prior cutaneous melanoma presented with 3 months of progressive left L5-distribution radicular pain. MRI showed a 1.0 × 2.0–cm well-circumscribed IDEM mass at L4–5 with left L5–S1 foraminal stenosis. Under intraoperative ultrasound localization and continuous multimodal neurophysiological monitoring, en bloc gross-total resection was achieved through L4–5 laminectomy. Histopathological analysis revealed a well-circumscribed vascular neoplasm with lobular endothelial architecture and no cytological atypia; immunohistochemical analysis (ERG, CD31, and CD34 positivity; HHV8, inhibin, and melanocytic marker negativity) established the diagnosis of EH. At the 7-week follow-up, gross-total resection was confirmed on postoperative MRI. LESSONS To the authors’ knowledge, this is the first reported intradural EH at any spinal level. Recognition of epithelioid endothelial morphology combined with a comprehensive vascular and melanocytic immunohistochemistry panel is essential for diagnosis and separates EH from more common intradural vascular differentials. https://thejns.org/doi/abs/10.3171/CASE26857