Pediatric brain tumors represent the second most common form of pediatric cancer and the most common solid malignancy. The most recent statistics available report findings from 2004, and they show that the incidence of pediatric brain tumors is approximately 1100 per year, representing 20% of all childhood cancers. These neoplasms also represent the second leading cause of cancer death in US children, and the sixth leading cause of death in US children overall.1,2 Survival for children with central nervous system (CNS) neoplasms, however, has dramatically risen over the past 30 years, with 5-year survival rates of 74%, up from 57% in 1977. Most of these results are due to a combination of improved chemotherapeutic regimens, more accurately targeted and dosed radiation, and safer, more accurate surgical resection techniques.1,3
The location of childhood tumors differs from those in adults. Most pediatric tumors occur in the posterior fossa, with medulloblastoma, juvenile pilocytic astrocytoma (JPA), and ependymoma making up the majority of these lesions.1-4
The etiology of childhood tumors is poorly understood. Although certain genetic syndromes are responsible for an increased risk of tumorigenesis (Table 25-1), the majority of tumors arise de novo. Certain environmental exposures have also been implicated in the development of tumors, including toxic chemicals, cigarette smoke, radiation, medications, home microwave ovens, cellular telephones, and electromagnetic fields. Of these, the only exposure that has a proven link to tumorigenesis is ionizing therapeutic radiation.5
++ Table Graphic Jump Location Table 25–1. Imaging Characteristics of Pediatric Tumors in the Posterior Fossa ||Download (.pdf)
Table 25–1. Imaging Characteristics of Pediatric Tumors in the Posterior Fossa
|Medulloblastoma||Juvenile Pilocytic Astrocytoma||Ependymoma|
|Location||Vermis||Cerebellar hemisphere||4th ventricle with spread through foramina of Luschka and Magendie|
|Noncontrast CT||Hyperdense||Hypodense||Iso- to hypodense|
Minimal to moderate
|Calcification||15%-20% Speckled||<10%||40%-50% Typically punctate|
|T1WI||Iso- to hypointense||Hypointense||Iso- to hypointense|
|T2WI/FLAIR||Iso- to hyperintense||Hyperintense||Iso- to hyperintense|
|Gadolinium||Enhances||Mural nodule enhances avidly||Variable enhancement|
|DWI||Restricted diffusion||Nonrestricted diffusion||Nonrestricted diffusion|
Brain tumors arise from multiple different cell lineages, and thus are a heterogeneous population of tumors. In this review, we will examine the following lesions: low-grade glioma, high-grade glioma, medulloblastoma, ependymoma, juvenile pilocytic astrocytoma, brainstem glioma, craniopharyngioma, and pineal region tumors (usually germ cell).
Pediatric brain tumors appear to arise from a different set of circumstances than do similar adult lesions. Craniopharyngiomas represent remains of embryonic cells that slowly differentiate over time, leading to growth of large lesions. Medulloblastomas are primitive neuroectodermal tumors (PNETs) that arise from similar but more aggressive embryonic rests. High- and low-grade gliomas are derived from newly differentiated glial cells that undergo multiple different ...