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Central nervous system (CNS) malignancies are the second most common malignancy in childhood and the most common form of solid tumor.8 Approximately 17% of all pediatric cancers arise in the CNS, of which 90% are located within the brain. In contrast to CNS tumors occurring in adults, pediatric CNS tumors have a relatively high rate of occurrence within the cerebellum and brain stem. Histologically, 52% of CNS tumors are astrocytomas, 21% medulloblastoma/primitive neuroectodermal tumor (PNET), 15% other gliomas, and 9% ependymomas. The incidence of CNS tumors is higher in males than in females and higher in whites than in blacks. In contrast to the age-specific pattern for childhood leukemia, CNS tumors do not demonstrate a marked variation in age. The incidence of childhood brain tumors has been reported to be increasing over the past several decades and is thus the topic of considerable speculation.9 Assessment of the secular trends in CNS tumors suggests that improvements in diagnostic technology may account for some of the observed increases.21
Review of the literature reveals that currently there are no known risk factors that account for a substantial proportion of CNS tumors in children.22–27 Factors known to be associated with an increased risk of CNS tumors include male gender (medulloblastoma/PNET, ependymomas), ionizing radiation (therapeutic doses), and genetic conditions such as neurofibromatosis, tuberous sclerosis, nevoid basal cell syndrome, Turcot syndrome, and Li-Fraumeni syndrome. Although the Li-Fraumeni syndrome is characterized by presence of germline p53 mutations, there is an absence of germline somatic mutations of that gene among sporadic pediatric brain tumors.28 Exposure to N-nitroso compounds, primarily through dietary intake of cured meats, has been actively pursued as an etiologic risk factor in childhood brain tumors, with results suggestive of an increased risk. More recently, interest has increased in the potential role of polyoma viruses (ie, simian virus 40, JC, BK) in the etiology of childhood brain tumors, but further investigation is necessary to elucidate the possible association and mechanisms.29–33