Subependymoma of the Conus Medullaris with Cystic Formation: Case Report and a Literature Review

BACKGROUND: Subependymoma in the spinal cord is very rare and usually occurs in the cervical cord. We report an exceptional case of subependymoma that occurred 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 offers an opinion about the cystic formation of the subependymoma. CASE DESCRIPTION: A 69-year-old woman experienced progressive limb weakness with a somatosensory abnormality for 3 months. Preoperative magnetic resonance imaging showed a cystic intramedullary lesion at the conus medullaris with a well-defined margin. A preliminary diagnosis of epidermoid cyst was made based on the imaging findings. During the operation, cystic formation of the tumor was found, and the tumor was completely removed. Pathology showed an uneven proliferation of glial cells, consistent with subependymal morphology, and the tumor was confirmed as subependymoma. CONCLUSIONS: We present an extremely rare case of cystic formation in subependymoma at the conus medullaris. Subependymoma should be included in the differential diagnosis of intramedullary cystic lesions. The breakdown of the blood-brain barrier and excessive extravasation may be potential mechanisms of cystic formation.