Introduction

This chapter will highlight current issues in the epidemiology of brain tumors. The areas of interest are the classification of brain tumors in epidemiologic studies, the spatial and temporal occurrence of brain tumors, and risk factors for brain tumors. More thorough reviews of the literature are available for adults and for children.

Classification of central nervous system neoplasia

The classification of intracranial tumors for epidemiologic studies is plagued by large variations in inclusion and exclusion criteria. A reasonable, working classification system is essential, however, for descriptive epidemiology and etiologic studies. There are several axes of classification of central nervous system neoplasia. There are anatomic location, histology, site of origin, and means of ascertainment.

The term “intracranial tumor” is generally used to refer to neoplasia of the nervous system and anatomic proximate tumors of the pituitary gland and craniopharyngeal duct. The major histological types of intracranial neoplasia are presented in Table 20.1. Because of the distinct occurrence, prognosis, and known or suspected etiologic factors for each type of neoplasia, there is little justification to combine all intracranial neoplasia. However, since most mortality and incidence data include all primary central nervous system (CNS) tumors, much of the descriptive epidemiology compares the rates of all primary central nervous neoplasia. Pituitary tumors, craniopharyngioma, and neurilemmoma, although often included as intracranial tumors, will not be addressed in this chapter.

Metastatic tumors of the brain may be derived from many primary sites and are of clinical significance because of seizures and other neurologic symptoms. The most common primary sites are the lungs in males and breast in females.