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.