Chordoid glioma of the third ventricle
Chordoid gliomas of the third ventricle are rare slow growing well-circumscribed low-grade tumors lesions that arise from the anterior wall or roof of the third ventricle.
Epidemiology
Epidemiological data is limited due to the rare nature of this finding and less than 100 cases have been published in the English language literature. In small case series and case reports, this mass is reported almost exclusively in the adult population with a female predilection (F:M 2:1). This entity has been described in patients from a wide range of ages, with most being between 30 and 60 years-of-age .
Clinical presentation
Patients typically present with symptoms of obstructive hydrocephalus including nausea and vomiting. Additional symptoms due to mass effect on the optic chiasm and tracts are also seen with some frequency, depending on the size of the tumor. More specifically, endocrine imbalances and dysautonomia have been reported due to involvement of the hypothalamus .
Pathology
Chordoid glioma of the third ventricle, along with astroblastomas and angiocentric gliomas, are grouped together as other gliomas in the current (2016) version of the WHO classification of CNS tumors. They are believed to originate from the ependymal cells of the lamina terminalis and are thus of glial origin, specifically of tanycytes, a type of ependymal cell. It is considered a WHO grade II tumor .
Microscopic appearance
Chordoid gliomas consist of clusters or cords of oval epithelioid cells embedded within a mucinous stroma with prominent lymphoplasmacytic infiltration and presence of Russell bodies . Older patients, in particular, may demonstrate a prominent fibrous component .
Mitoses are rare and necrosis is not present.
Immunophenotype
The immunophenotype of chordoid gliomas reflects their glial origin .
- GFAP: positive
- TTF1: positive
- vimentin: positive
- CD43: positive
- S100, cytokeratin and EMA: variable
- Ki-67 index: <5%
- IDH: negative
Radiographic features
CT
These tumors appear as ovoid hyperdense masses on non-contrast CT. Enhancement is variable on post-contrast imaging, although the majority of these masses will avidly and uniformly enhance. Associated obstructive hydrocephalus findings are also expected
MRI
The majority of chordoid gliomas demonstrate appearances and signal characteristic reminiscent of intraventricular meningiomas. They appear as well circumscribed lesions appearing to arise from the anterior aspect of the third ventricle, with a hypothalamic component often seen.
- T1: isointense
- T2
- mildly hyperintense
- edema in the thalamus may be visible
- a minority may have peripheral cystic changes
- T1 C+: avid enhancement
Treatment and prognosis
Most lesions are treated with surgical resection with the intent of a surgical cure although given their location and involvement of the hypothalamus complete surgical resection is often not possible without risking significant morbidity .
In subtotal resections, Gamma knife radiosurgery has been reported with good effect. Chemotherapy and/or radiotherapy have been reported to be ineffective.
History and etymology
These are a relative new clinicopathologic entity first described by Brat et al. in 1998 .
Differential diagnosis
Both on imaging and histology a diagnostic consideration is an intraventricular meningioma (particularly chordoid meningioma). Identifying a site of origin in the hypothalamus can be helpful in suggesting a chordoid glioma. Immunohistochemistry is particularly helpful (meningiomas will be GFAP and CD34 negative ).
Other entities to be considered include:
