Rare Variants of Ependymoma: A Report of Four Cases and a Review of the Literature

Ependymomas are brain tumors that have a wide spectrum of morphological patterns. Rare or unusual patterns of ependymoma can resemble other neoplasms and result in erroneous diagnosis, and management. Four out of 22 ependymoma cases in the pathology archive of King Abdulaziz University Hospital in the last decade had these patterns. The fi rst case was of ependymoma with multinodular growth and diff erent types of ependymal diff erentiation, including subependymoma, classic ependymoma, and astroblastoma. Dysplastic neurons were associated with the neoplastic growth. This combination can be interpreted as ganglioglioma (i.e., with ependymoma representing the glial component, World Health Organization grade I) or alternatively as ependymoma with dysplastic neurons (World Health Organization grade II). The second case was of a rare variant of intracranial extra-axial ependymoma with lobular and papillary architecture. The third case was of a previously unreported combination of clear cell and giant cell ependymoma. The fourth case was of epithelioid ependymoma with fi brillary background and a peculiar arrangement of the tight clustered epithelioid cells. This report expands the morphological spectrum of ependymoma by introducing diff erent, previously unreported combinations of patterns that were observed in individual tumors, as well as rare locations andarchitectures.

Novel pathological abnormalities of deep brain structures including dysplastic neurons in anterior striatum associated with focal cortical dysplasia in epilepsy

Object Some patients are not seizure free even after epileptogenic cortical resection. The authors recently described a case of frontal lobe epilepsy cured after the resection of periventricular white matter and striatum, in which dysplastic neurons were revealed. The authors attempted to confirm similar cases. Methods They reviewed the records of 8 children with frontal lobe epilepsy who had daily (7) or monthly (1) seizures and underwent resections including deep brain structures. Results Five patients underwent multiple resections. Neuroimaging of the deep structures showed the transmantle sign in 3 patients, ictal hyperperfusion in 6, reduced iomazenil uptake in 2, and spike dipole clustering in 6. All patients became seizure free postoperatively. Focal cortical dysplasia of various types was diagnosed in all patients. Dysmorphic neurons were found in the cortex and subcortical white matter of 5 patients. The striatum was verified in 3 patients in whom dysmorphic neurons were scattered. In the periventricular white matter, prominent astrocytosis was evident in all cases. Conclusions Pathological abnormalities such as dysmorphic neurons and astrocytosis in deep brain structures would play a key role in epileptogenesis.

Glutamate clearance mechanisms in resected cortical dysplasia

Object Changes in the expression of glutamate transporters (GLTs) may play a role in the expression of epileptogenicity. Previous studies have shown an increased number of neuronal GLTs in human dysplastic neurons. The expression of glial and neuronal GLTs and glutamine synthetase (GS) in balloon cells (BCs) and BC-containing cortical dysplasia has not been studied. Methods The authors analyzed neocortical samples that were resected in 5 patients who had cortical dysplasia–induced medically intractable focal epilepsy and who underwent extraoperative prolonged electrocorticographic (ECoG) recordings. The expressions of glial (GLT1/EAAT2) and neuronal (EAAT3, EAAC1) GLTs and GS proteins were immunohistochemically studied in all 5 resected samples. The authors also assessed in situ colocalization of GLTs and GS with neuronal and glial markers. Results Balloon cell–containing cortical dysplasia lesions did not exhibit ictal patterns on prolonged extraoperative ECoG recordings. There was a differential expression of glial and neuronal GLTs in BCs and dysplastic neurons: the majority of BCs highly expressed glial but not neuronal GLTs. Dysplastic neurons showed increased immunohistochemical staining with neuronal EAAT3 but not with EAAT2/GLT1. Moreover, only glial fibrillary acidic protein–positive BCs also expressed GS. Conclusions There is a differential GLT expression in dysplastic and balloon cells. The presence of glial GLTs and GS in balloon cell cortical dysplasia suggests a possible antiepileptic role for BCs and is consistent with the reported increased epileptogenicity in GLT1-deficient animals.