Chordoid glioma of the third ventricle WHO 2007 grade II
Chordoid glioma is a rare tumor of the third ventricle, firstly proposed as a distinct entity by Brat et al in 1998 (1). To our knowledge (December, 2011), 74 cases (including our case) have been reported. The tumor predominantly occurs in adult women with a female to male ratio of 1.6 to 1 and the mean age at presentation at 45.25 years of age. Most patients have headache, visual symptoms, and memory disturbances. Other symptoms are lethargy, somnolence, endocrine disturbance such as hypothyroidism and diabetes insipidus, and symptoms caused by space occupying lesion and obstructive hydrocephalus are also observed in some patients.
Chordoid glioma mainly locates at the third ventricle or nearby structures, hence the name "Chordoid glioma of the third ventricle". Unusual locations without third ventricular association that have been reported are parieto-temporal region (3) and thalamic pulvinar area (5). The tumors arising in or involving the third ventricle, especially at the anterior part, are considered in the differential diagnosis for chordoid glioma (4). These tumors include ependymoma, pilocytic astrocytoma, central neurocytoma, choroid plexus papilloma, pituitary adenoma, suprasellar meningioma, and craniopharyngioma. Other lesions such as lymphoma, aneurysm, granular cell tumor of neurohypophysis, histiocytosis, sarcoidosis, and germ cell tumors may also involve the third ventricle. On CT, chordoid glioma is a well circumscribed hyperdensity mass with homogeneous contrast enhancement. On MRI, the tumor is a solid or solid-cystic mass. It typically shows isosignal intensity on T1, hypersignal intensity on T2, with homogeneous enhancement (6).
Histologically, chordoid glioma is composed of clusters, and cords of relatively uniform epithelioid tumor cells in variable mucinous background. Mitosis is rare. Lymphoplasmacytic infiltrates with numerous Russel bodies are present within the lesion and adjacent brain parenchyma. Reactive astrocytes and Rosenthal fibers are also noted in the adjacent non-neoplastic brain tissue (2).
Histologic differential diagnoses for chordoid glioma are chordoid meningioma, myxoid chondrosarcoma, and chordoma (9). Immunohistochemically, strong diffuse reactivity for GFAP distinguish chordoid glioma from its mimics. The other antibodies that reported to be positive in chordoid glioma are vimentin, S-100 protein, EMA, CD34 and CD99 (6,8). Rare positivity to neurofilament protein, synaptophysin and p53 are also noted (6). The tumor shows reactivity to EGFR and NF2 without amplication of associate proto-oncogene (7).
The ependymal nature of chordoid glioma has been suggested by findings on electron microscopy and positivity to CD99 (8). Ultrastructurally, the tumor exhibits features of ependymal differentiation which include intermediate filaments, intercellular lumina apical microvilli, hemidesmosomes, and basal lamina (2).
Surgical treatment is the primary option for chordoid glioma, but its common location either in or nearby third ventricle usually precludes gross total resection without complications. Common postoperative complications, in descending order, include diabetes insipidus, cognitive dysfunction, pulmonary embolus, and hypothalamic dysfunction. Since there are a limit number of cases, the role of radiotherapy and radiosurgery in subtotal or partially resected tumors is uncertain. There is no report of the use of chemotherapy in chordoid glioma (6).
Contributed by Jantima Tanboon, MD; Taweesak Aurboonyawat, MD; Orasa Chawalparit, MD