Chapter 33: Central Nervous System Tumors in Childhood

INTRODUCTION

Central nervous system (CNS) tumors are the most common solid tumor of childhood and are the leading cause of death in children diagnosed with cancer. The number of children 0 to 19 years old in the United States diagnosed with a CNS tumor is approximately 6.21 per 100,000 per year as estimated by the Central Brain Tumor Registry of the United States.¹

CNS tumors have variable treatments and prognoses based on their location, histology, immunohistochemistry, and molecular classification, which has been most recently updated in 2021 by the World Health Organization Classification of Tumors of the Central Nervous System (WHO CNS5).² The classification of tumors of the CNS is constantly being updated as new information is learned. Recently, WHO CNS5 updated the classifications of numerous pediatric CNS tumors, including pediatric diffuse low-grade gliomas and diffuse high-grade gliomas; circumscribed astrocytic gliomas; glioneuronal tumors and neuronal tumors, including dysembryoplastic neuroepithelial tumors; ependymal tumors; choroid plexus tumors; embryonal tumors such as medulloblastoma; pineal tumors; cranial and paraspinal nerve tumors; meningiomas; mesenchymal and nonmeningothelial tumors; melanocytic tumors; hematolymphoid tumors, including lymphomas and histiocytic tumors; germ cell tumors; tumors of the sellar region; and metastases to the CNS.

Pediatric low-grade gliomas are the most common brain tumor in childhood. They occur throughout the CNS and in a broad range of ages with multiple different tumor histologies. When low-grade gliomas can be completely surgically resected, they may not require further treatment. However, tumors that occur in critical or inaccessible regions of the brain are frequently unable to undergo complete surgical resection.

Medulloblastoma, a common pediatric embryonal tumor, is the most common malignant brain tumor of childhood. It is found in the cerebellum, although it may metastasize to other CNS locations, and is typically seen in children younger than 10 years old. Fortunately, it is associated with increased survival rates due to advances in risk stratification and combination therapies including radiation to the craniospinal axis and chemotherapy.

The second most common malignant brain tumor of childhood is ependymoma, which is found throughout the CNS. Ependymomas most frequently occur in children younger than 5 years old with variable prognosis. These are typically treated with surgery and radiation, with variable use of chemotherapy. Unlike other CNS tumors, the risk of relapse continues long into typical survivorship.

High-grade gliomas occur at all ages and anywhere in the CNS and lead to poor outcomes. Diffuse intrinsic pontine gliomas are a particularly aggressive type of glioma centered in the pons of the brainstem. Despite radiation or other treatments, these tumors almost always lead to devastating outcomes with a very poor survival rate. Overall median survival is 1 year, with a 2-year overall survival rate of less than 10%.³

Spinal tumors are rare and account for approximately 5% of all CNS tumors in children and adolescents.¹

CLINICAL PRESENTATION