Third ventricular tumor classification

Tumors of the third ventricle are classified into primary tumors, such as colloid cysts, choroid plexus papillomas, and ependymomas, or secondary tumors, such as craniopharyngiomas, optic nerve gliomas, pineal tumors, and meningiomas.

The most commonly found pathologic processes are related to the anterior recesses of the third ventricle and are of sellar-suprasellar or hypothalamic-chiasmatic origin. Lesions deforming the posterior aspect of the third ventricle most commonly arise from the pineal gland, although tectal plate and inferior thalamic masses may obstruct the aqueduct, resulting in dilatation of the third ventricle. Lesions may arise in the floor of the third ventricle, such as hypothalamic hamartoma, or be extrinsic masses elevating the floor. The most common mass of the foramen of Monro is a benign colloid cyst. Most intraventricular masses are lesions arising in or metastatic to the choroid plexus ¹⁾.

Colloid Cyst of the third Ventricle

Some craniopharyngiomas may arise primarly withhin the third ventricle

The more common anterior third ventricular neoplasms are hypothalamic astrocytoma and suprasellar craniopharyngioma. Choroid plexus papilloma, germinoma, teratoma, and ependymoma occasionally are seen in children. Ten percent of CPPs involve the third ventricle and occur primarily in children younger than 5 years of age. Fifteen percent of all supratentorial ependymomas present within the third ventricle. Epidermoid and dermoid tumors occur uncommonly in the anterior third ventricle.

A number of nonneoplastic entities that occur in the anterior body of the third ventricle deserve mention. Colloid cysts represent the most common anterior third ventricular mass demonstrated in adults. These lesions can occur in adolescents and young adults but seldom occur in young children. Both microsurgical and endoscopic procedures have been performed to resect these lesions, and the results have been good. Histiocytosis represents a common anterior third ventricular mass lesion found in children; these lesions tend to arise in the suprasellar region from the floor of the third ventricle and may invade the hypothalamus. Children with these lesions can present with evidence of pituitary-hypothalamic dysfunction and bony skeletal lesions. There appears to be a slight male predominance. The goal of surgical intervention is primarily to obtain a biopsy sample to determine a diagnosis, as these lesions are extremely radiosensitive. Cysticercosis is the most common parasitic infection involving the CNS; it is caused by the intestinal tapeworm Taenia solium and is endemic in some areas of Mexico and certain Third World countries. In the United States, cysticercosis is a rare entity more commonly found in the Western and Southwestern regions. The favored location of cystic lesions is either meningeal or within brain parenchyma. Approximately 12 to 18% are located intraventricularly, possibly gaining access via the choroid plexus. Ventricular involvement is associated with higher patient morbidity and mortality. Cysts may travel via the ventricular system and can cause obstructive hydrocephalus, although the classic clinical presentation in children involves repeated bouts of meningitis rather than hydrocephalus.

Third ventricular ependymoma.

Posterior third ventricular (PTV) tumors form less than (<) 1% all intracranial tumors, of which meningiomas constitute 1-6%.

see Chordoid glioma of the third ventricle

Central neurocytomas are rare WHO Grade II neuronal tumors. They are generally attached to the septum pellucidum within the lateral ventricles, and less frequently occur within the third ventricle.