Chordoid glioma of the third ventricle: report of a rapidly progressive case

Benign Glioma

Benign glioma broadly refers to a heterogeneous group of slow-growing glial tumors with low proliferative rates and a more indolent clinical course. These tumors may also be described as "low-grade" glioma (LGG) and are classified as WHO grade I or II lesions according to the Classification of Tumors of the Central Nervous System (CNS) (Louis et al. in Acta Neuropathol 114:97-109, 2007). Advances in molecular genetics have improved understanding of glioma tumorigenesis, leading to the identification of common mutation profiles with significant treatment and prognostic implications. The most recent WHO 2016 classification system has introduced several notable changes in the way that gliomas are diagnosed, with a new emphasis on molecular features as key factors in differentiation (Wesseling and Capper in Neuropathol Appl Neurobiol 44:139-150, 2018). Benign gliomas have a predilection for younger patients and are among the most frequently diagnosed tumors in children and young adults (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). These tumors can be separated into two clinically distinct subgroups. The first group is of focal, well-circumscribed lesions that notably are not associated with an increased risk of malignant transformation. Primarily diagnosed in pediatric patients, these WHO grade I tumors may be cured with surgical resection alone (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). Recurrence rates are low, and the prognosis for these patients is excellent (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). Diffuse gliomas are WHO grade II lesions with a more infiltrative pattern of growth and high propensity for recurrence. These tumors are primarily diagnosed in young adult patients, and classically present with seizures (Pallud et al. Brain 137:449-462, 2014). The term "benign" is a misnomer in many cases, as the natural history of these tumors is with malignant transformation and recurrence as grade III or grade IV tumors (Jooma et al. in J Neurosurg 14:356-363, 2019). For all LGG, surgery with maximal safe resection is the treatment of choice for both primary and recurrent tumors. The goal of surgery should be for gross total resection (GTR), as complete tumor removal is associated with higher rates of tumor control and seizure freedom. Chemotherapy and radiation therapy (RT), while not typically a component of first-line treatment in most cases, may be employed as adjunctive therapy in high-risk or recurrent tumors and in some select cases. The prognosis of benign gliomas varies widely; non-infiltrative tumor subtypes generally have an excellent prognosis, while diffusely infiltrative tumors, although slow-growing, are eventually fatal (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). This chapter reviews the shared and unique individual features of the benign glioma including diffuse glioma, pilocytic astrocytoma and pilomyxoid astrocytoma (PMA), subependymal giant cell astrocytoma (SEGA), pleomorphic xanthoastrocytoma (PXA), subependymoma (SE), angiocentric glioma (AG), and chordoid glioma (CG). Also discussed is ganglioglioma (GG), a mixed neuronal-glial tumor that represents a notable diagnosis in the differential for other LGG (Wesseling and Capper 2018). Ependymomas of the brain and spinal cord, including major histologic subtypes, are discussed in other chapters.

Chordoid glioma: a rare old foe but a new pathological and radiological presentation

Chordoid glioma (CG) is a rare WHO Grade II neoplasm of the anterior third ventricle. We report two cases of CG with new presentation in terms of histopathology and location: a case of CG with osseous metaplasia evident on imaging, and another CG, unusually located in the posterior portion of the third ventricle.

Chordoid Glioma Infiltrating Optic Structures

Chordoid glioma of the third ventricle (CGTV) is a rare, slow-growing, World Health Organization Grade II glial tumor, with stereotyped localization in the anterior third ventricle. Despite being considered a noninvasive tumor, CGTV is usually associated with a poor clinical outcome due to its close proximity to important cerebral structures, such as the hypothalamus and visual pathways. Our patient with CGTV experienced visual involvement, but after subtotal surgical resection showed no evidence of progression at 5-year follow-up.

Chordoid glioma: an entity occurring not exclusively in the third ventricle

Chordoid gliomas are extremely rare entities, which are generally considered occurring exclusively in the third ventricle. Despite the low-grade histological grade, aggressive behaviors have been reported in literatures. Due to the low morbidity, the origins, clinical, and radiological features, management and prognosis are still yet to be well elucidated. We retrospectively reviewed the clinical profiles from a series of 6 patients with chordoid gliomas. All patients underwent surgical treatment, and the diagnoses were based on histopathological examinations. Magnetic resonance imaging (MRI) was performed perioperatively. Follow-up outcomes were presented. This case series consisted of three male and three female patients (age range 27-67 years; mean age 43.3 years). MRI results showed tumors in the third ventricle (4/6), temporal-parietal-occipital lobe involving the lateral ventricle (1/6), and cerebellar hemisphere (1/6). Three tumors were solid, and the others were cystic-solid. Hydrocephalus was present in one patient. The T1-weighted imaging showed hypo- to isointensity, and T2-weighted imaging showed iso- to hyperintensity; enhancement was homogeneous (4/6) or heterogeneous (2/6). Diffusion-weighted imaging showed no evidence of restricted diffusion. Magnetic resonance spectrum showed an elevated choline value and reduced N-acetylaspartate value. Gross total resection was achieved in all patients, and during an average follow-up period of 35.8 months, no recurrence was noted. Chordoid gliomas can occur outside the third ventricle with a great diagnostic challenge. The MRI characteristics suggest a low-grade tumor, and the accurate diagnosis depends on pathological criteria. Complete surgical resection is associated with a favorable outcome.