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Brain tumors account for 85% to 90% of all primary central nervous system (CNS) tumors. Available registry data from the Surveillance, Epidemiology, and End Results (SEER) database for 1996 to 2000 indicate that the combined incidence of primary invasive CNS tumors in the United States is 6.6 per 100,000 persons per year with an estimated mortality of 4.7 per 100,000 persons per year. Worldwide, approximately 176,000 new cases of brain and other CNS tumors were diagnosed in the year 2000, with an estimated mortality of 128,000. In general, the incidence of primary brain tumors is higher in whites than in blacks, and mortality is higher in males than in females.
Anaplastic astrocytoma and glioblastoma account for approximately 38% of primary brain tumors; meningiomas and other mesenchymal tumors account for approximately 27%. Other less common primary brain tumors include pituitary tumors, schwannomas, CNS lymphomas, oligodendrogliomas, ependymomas, low-grade astrocytomas, and medulloblastomas, in decreasing order of frequency. Schwannomas, meningiomas, and ependymomas account for as much as 79% of primary spinal tumors. Other less common primary spinal tumors include sarcomas, astrocytomas, vascular tumors, and chordomas, in decreasing order of frequency. The familial tumor syndromes (and respective chromosomal abnormalities that are associated with CNS neoplasms) include neurofibromatosis type I (17q11), neurofibromatosis type II (22q12), von Hippel-Lindau disease (3p25-26), tuberous sclerosis (9q34, 16p13), Li-Fraumeni syndrome (17p13), Turcot syndrome type 1 (3p21, 7p22), Turcot syndrome type 2 (5q21), and nevoid basal cell carcinoma syndrome (9q22.3).[6,7]
Few definitive observations on environmental or occupational causes of primary CNS tumors have been made. Exposure to vinyl chloride may predispose to the development of glioma. Epstein-Barr virus infection has been implicated in the etiology of primary CNS lymphoma. Transplant recipients and patients with the acquired immunodeficiency syndrome have substantially increased risks for primary CNS lymphoma.[2,10] (Refer to the PDQ summary on Primary CNS Lymphoma Treatment for more information.)
The clinical presentation of various brain tumors is best appreciated by considering the relationship of signs and symptoms to anatomy. General signs and symptoms include headaches; gastrointestinal symptoms such as nausea, loss of appetite, and vomiting; and changes in personality, mood, mental capacity, and concentration. Whether primary, metastatic, malignant, or benign, brain tumors must be differentiated from other space-occupying lesions such as abscesses, arteriovenous malformations, and infarction, which can have a similar clinical presentation. Other clinical presentations of brain tumors include focal cerebral syndromes such as seizures. Seizures are a presenting symptom in approximately 20% of patients with supratentorial brain tumors and may antedate the clinical diagnosis by months to years in patients with slow-growing tumors. Of all patients with brain tumors, 70% with primary parenchymal tumors and 40% with metastatic brain tumors develop seizures at some time during the clinical course.