All these tumors are rare. They constitute from 1 to 3 percent of intracranial tumors, depending on how wide a range of neoplasms one chooses to include (see in the following text). Occasionally, cerebral deposits of these types of tumors will occur as a metastasis from a sarcoma in another organ. Almost all others are primary in the cranial cavity and exhibit as one of their unique properties a tendency to metastasize to nonneural tissues—a decidedly rare occurrence with primary glial tumors. It is a disturbing fact that a few sarcomas have developed 5 to 10 years after cranial irradiation or, in one instance among 3,000 patients related to us by R.D. Adams, after proton beam irradiation of the brain. Fibrosarcomas have occurred after radiation of pituitary adenomas and osteogenic sarcoma, after other types of radiation, all localized to bone or meninges. Our experience with hemangiopericytoma has included to three intracranial lesions that simulated meningiomas and two others that arose in the high cervical spinal cord and caused subacute quadriparesis, initially misdiagnosed as an acute polyneuropathy.
A number of other cerebral tumors, described in the literature as sarcomas, are probably tumors of other types. The rapidly growing, highly malignant “monstrocellular sarcoma” of Zülch or “giant cell fibrosarcoma” of Kernohan and Uihlein, so named for their multinucleated giant cells, were reinterpreted by Rubinstein (1972) as a form of giant cell glioblastoma or mixed glioblastoma and fibrosarcoma. The “hemangiopericytoma of the leptomeninges,” also classified by Kernohan and Uihlein as a form of cerebral sarcoma, is considered by Rubinstein (1972) to be a variant of the angioblastic meningioma.
In the WHO classification, a gliosarcoma is categorized with other gliomas and a granulocytic sarcoma is listed under the hematopoetic tumors but restricting the term to these does not fully capture the range and unusual behaviors of most cranial sarcomas.
Patients Who Present Primarily With Signs of Increased Intracranial Pressure (Medulloblastoma, Ependymoma of the Fourth Ventricle, Hemangioblastoma of the Cerebellum, Pinealoma, Colloid Cyst of the Third Ventricle and Rare Related Tumors)
Upon first presentation, a number of patients with brain tumors show the characteristic symptoms and signs of increased intracranial pressure, namely periodic bifrontal and bioccipital headaches that awaken the patient during the night or are present upon awakening, projectile vomiting, mental torpor, unsteady gait, sphincteric incontinence, and papilledema. In the tumors listed above, most of the symptoms and the associated increase in ICP are the result of hydrocephalus rather than being attributable to the tumor mass.
The diagnostic problem is resolved by CT or MRI, which is obtained in patients with symptoms of increased intracranial pressure, with or without focal signs. In addition to the tumors listed in the heading above, others that may present in this way are central neurocytoma, craniopharyngioma, and a high spinal cord, cervicomedullary junction tumor. In addition, with some of the gliomas discussed in the preceding section, increased intracranial pressure may occasionally precede the first focal cerebral signs.
Medulloblastoma, Neuroblastoma, and Retinoblastoma
Medulloblastoma Medulloblastoma is an invasive and rapidly growing tumor, mainly of childhood, that arises in the posterior part of the cerebellar vermis and neuroepithelial roof of the fourth ventricle in children. It accounts for 20 percent of childhood brain tumors. Rarely, it presents elsewhere in the cerebellum or other parts of the brain in adults (Peterson and Walker).