Primary brain tumors are a diverse group of neoplasms arising from different cells of the central nervous system (CNS). Although uncommon, there is evidence that the incidence of these tumors has been rising for as much as fifty years. (See "Classification of gliomas", section on 'Histopathologic and molecular classification'.)
The incidence of primary malignant and benign brain tumors will be reviewed here. Risk factors for the development of brain tumors as well as the incidence of brain metastases are discussed separately. (See "Risk factors for brain tumors" and "Overview of the clinical manifestations, diagnosis, and management of patients with brain metastases".)
SOURCES OF DATA
The Central Brain Tumor Registry of the United States (CBTRUS) includes both benign and malignant lesions in its data collection. The CBTRUS was established in 1992 and compiles information from twelve state cancer registries . Earlier data from the SEER program and other US cancer registries were limited to malignant brain tumors; however, as of 2004, data on nonmalignant brain tumors have been systematically collected by US cancer registries after the passage of Public Law 107-260, the Benign Brain Tumor Cancer Registries Amendment Act .
Inclusion of benign lesions is important to properly evaluate differences in etiology and to assess the potential impact of intervention studies. Benign lesions often produce the same neurologic symptoms as malignant tumors and distinguishing between benign and malignant based upon clinical grounds can be difficult. In addition, both benign and malignant lesions are frequently treated similarly with either surgical intervention or radiation therapy, and many malignant brain tumors probably originate from benign precursors. (See "Classification of gliomas", section on 'Histopathologic and molecular classification'.)
INCIDENCE AND MORTALITY
The US incidence rate for primary brain and nervous system tumors in adults (aged 20 years or older) is estimated to be 27.4 per 100,000 persons (data from 50 cancer registries, 2006 to 2010) . Approximately one-third of tumors are malignant and the remainder are benign or borderline malignant [2,3].