Overall, tumors of the CNS in children are more prevalent amongst males (1.29:1 male to female ratio). They tend to be slightly more frequent in the infratentorial region than supratentorial region [1]. However, for children under three years of age, tumors more frequently occur in the supratentorial region (59 %) [2]. It has been reported that the most common histological diagnoses are astrocytoma (37.6 %), medulloblastoma (17.7 %), ependymoma (9.9 %), craniopharyngioma (7.3 %), and germ cell tumors (4.4 %) [1]. This distribution, however, varies with age. The distribution of cases with a histological diagnosis of ependymoma or medulloblastoma decreases with age. Both account for a greater percentage of diagnoses in patients under 4 years of age than in older age groups. In contrast, the percentage of cases of astrocytoma is fairly constant across the pediatric age groups.

Determining an exact incidence figure for the occurrence of tumors of the CNS can be confusing. Varying estimates have been reported depending on the source of the data, the age in question, and the time period used. What is known about the incidence of childhood tumors of the CNS has been obtained using information from regional or national databases. Caution must be taken in the interpretation of these figures. Much of the data that has been reported regarding primary brain and CNS tumors has been limited to primary malignant tumors. Less often have nonmalignant tumors been included. Often only summary estimates of tumor location and histology are provided. The histological classifications can be different between geographic locations and have also changed over time. A lack of agreement on diagnostic criteria and the small size of available tissue mean that the histological diagnoses are infrequently confirmed by a second review. As well, the ages used often have varied between reported studies. The populations from which the cases are drawn have varied, with varied degrees of completeness. This has resulted in a variation of the reported incidence rates of tumors of the CNS between the populations under study and the time period of interest.

Despite these limitations, the reported incidence rates have been similar. For example, in the United States, there are principally three large, centralized databases: the National Cancer Data Base (NCDB), the Central Brain Tumor Registry of the United States (CBRTRUS), and the Surveillance, Epidemiology, and End Results (SEER) database [3]. Each covers a different population base. The NCDB is sponsored by the American College of Surgeons and the American Cancer Society. The case ascertainment is derived from hospital-based follow-up of all primary tumors from institutions accredited by the American College of Surgeons. The collection of data on malignant tumors is mandatory for each participating hospital as part of its accreditation; however, data collection for benign tumors is voluntary. Though it can provide valuable information on diagnosis and outcome, it was not designed to provide estimates of incidence rates. However, annually the American Cancer Society, Centers for Disease Control and Prevention, the National Cancer Institute, and the North American Association of Central Cancer Registries collaborate to provide incidence rates in the United States. For the period 1992, the reported overall incidence was 4.8 per 100,000 children [4]. For the same period, CBTRUS, a population-based registry which draws data from several regional registries in the United States reported an incidence rate of 3.76 per 100,000 persons [5]. In comparison, SEER, a population-based national cancer registry program funded by the National Cancer Institute, reported an incidence rate of 3.5 per 100,000 [6]. For the same time period, the European incidence rate for persons 14 years or less was reported to be 2.9 per 100,000 [7]. However, within Europe, the incidence figures have varied. Denmark, based on the Danish Cancer Registry, Danish Hospital Discharge diagnosis, and clinical databases from major Danish centers, had an incidence rate of 3.95 per 100,000 population years [8]. In Germany, a rate of 2.6 per 100,000 children under age of 15 years was reported. This figure was based on data obtained from a tumor registry involving130 pediatric hospitals and centers for pediatric oncology in Germany [9]. For the same time period, the Japanese incidence was reported as 3.43 per 100,000 children [10].