LAUSR

BACKGROUND Subependymoma in the spinal cord is very rare and usually occurs in the cervical cord. Here, we report an exceptional case of subependymoma that occurs at the conus medullaris with cystic formation. This article reviews the literature on subependymoma in the conus medullaris, discusses its clinical manifestations, imaging findings and differential diagnoses, and puts forward a conjecture about the cystic formation of the subependymoma. CASE DESCRIPTION A 69-year-old woman suffered from progressive limb weakness with a somatosensory abnormality for 3 months. Preoperative magnetic resonance imaging (MRI) showed a cystic intramedullary lesion at the conus medullaris, with a well-defined margin. A preliminary diagnosis of epidermoid cyst was given based on the MRI findings. During the operation, cystic formation of the tumor was found, and the tumor was completely removed. The pathological results described an uneven proliferation of glial cells, consistent with subependymal morphology, and the tumor was confirmed as subependymoma. CONCLUSIONS Our report presents an extremely rare case of cystic formation in subependymoma at the conus medullaris. We propose that subependymoma should be included in the differential diagnoses of intramedullary cystic lesions, and we suggest that the breakdown of the blood-brain barrier and excessive extravasation may be potential mechanisms of cystic formation.