Infratentorial and Intraparenchymal Subependymoma in the Cerebellum: Case Report
A 28-year-old man was referred to our institution for a brain tumor that was detected on brain computed tomography (CT) performed at an outside hospital for intermittent headache. He had other non-neurologic symptoms, other than intermittent headache, for the past 1 year. The patient was previously healthy with unremarkable past medical history. A neurological examination revealed no abnormal features, and initial lab findings were normal. Pre-contrast CT revealed a well-defined cystic and solid intraaxial mass with internal calcifications in the cerebellum, which measured 4.3 × 3.5 cm (). Magnetic resonance image (MRI) revealed a mural nodule within the cystic mass. The mural nodule showed iso-to-hypointensity (relative to normal white matter) with multiple nodular high-signal intensities, suggesting calcifications on the T1-weighted image and hyper intensity on the T2-weighted image (). There was no evidence of peritumoral edema around the mass and no enhancement of the mural nodule or cyst wall on the gadolinium-enhanced T1-weighted image. Diffusion-weighted image showed iso- or low-signal intensity without diffusion restriction while the same lesion was increased ADC relative to brain parenchyma (). The mass was located near and displaced the fourth ventricle; however, it did not communicate with the ventricle, and normal parenchyma was clearly identified between the mass and the fourth ventricle on the thin-section three-dimensional T1-weighted images (). Cerebral angiograms demonstrated a rather hypovascular mass; neither feeding vessels nor tumor staining was visualized (). The patient underwent suboccipital craniotomy. The cerebellum showed mild bulging, and a yellowish-colored mass was identified via a supracerebellar approach. During the dissection of the mass from the cerebellum, fluid gushed out from patchy gray mass, which was composed of a gelatinous material. Within the surgical field, there was a sharp demarcation between the mass and the surrounding normal tissue, and there was no evidence that the mass was connected with the fourth ventricle.\nHistopathological analysis revealed a clustered cellular neoplastic proliferation with islands of high nuclear density and dense and abundant fibrillary matrices. The tumor cell nuclei were round and isomorphic, but active mitosis was not observed (). Occasional vascular pseudorosettes and calcifications were also seen. There was no evidence of atypia, vascular endothelial proliferation or necrosis. Immunohistochemical analyses were positive for glial fibrillary acidic protein and epithelial membrane antigen and negative for Ki-67, which supported the diagnosis of subependymoma.\nThe postoperative follow-up MRI revealed a total removal of the tumor resection; the normal cerebellar tissue remained well between the fourth ventricle and the postoperative parenchymal defect. This observation supports our hypothesis that the tumor did not contact the fourth ventricle. The patient was discharged without neurologic sequelae 10 days after surgery.