Giant infiltrative myxopapillary ependymoma of filum terminale with sacral erosion: a case report and literature review

Introduction and importance: Myxopapillary ependymoma (MPE) is a rare neuroepithelial tumor predominantly localized to the filum terminale. While traditionally viewed as indolent, its reclassification to World Health Organization (WHO) Grade 2 in 2021 reflects a significant risk of recurrence and neuraxial dissemination. Giant infiltrative variants (>10 cm) with sacral erosion are exceptionally rare and present formidable surgical and oncological challenges. Presentation of case: A 30-year-old female presented with a 2.5-year history of progressive radiculopathy, culminating in paraparesis (MRC Grade 2/5), urinary and fecal incontinence. Neuroimaging revealed a massive, heterogeneously enhancing intradural mass (19 × 8.6 × 6.3 cm) extending from the conus medullaris (L1) to the sacrum, demonstrating significant sacral erosion, foraminal expansion, and presacral extension. The patient underwent an L3–L4 laminectomy for decompression and tumor reduction. Due to dense adherence to the cauda equina, a subtotal resection (approximately 30–40%) was performed to preserve neurological integrity. Histopathology confirmed WHO Grade 2 MPE with a low Ki-67 index (<2%). Postoperative residual disease was managed with adjuvant external beam radiotherapy (50 Gy in 25 fractions). At 5 months, the patient regained independent ambulation with significant motor recovery and achieved complete resolution of sphincter dysfunction. Clinical discussion: The extent of resection remains the primary prognostic indicator; however, in “giant” infiltrative cases, gross total resection is often precluded by dense neural adherence. In such scenarios, subtotal resection combined with adjuvant radiotherapy (50–54 Gy) is crucial for achieving local control and facilitating neurological recovery. The aggressive local destruction observed here, despite a low proliferative index, underscores the unpredictable nature of MPE. Conclusion: Giant MPEs can exhibit locally aggressive behavior and significant anatomical destruction. A multidisciplinary approach utilizing strategic subtotal resection, adjuvant radiotherapy, and rigorous longitudinal surveillance is vital for managing extensive lesions while prioritizing functional outcomes.