Brain Tumor

Basics

Description

A primary neoplasm arising in the central nervous system (CNS)

Epidemiology

Most common solid neoplasm of childhood (second to leukemia in overall incidence)
Most common cause of cancer death in children 0 to 14 years
Slight male predominance
Majority arise infratentorially (within cerebellum or brainstem) in children 1 to 14 years of age.
Majority arise supratentorially in children <1 year of age.

Incidence

Incidence >3,000 new cases/year
5.4 cases/100,000 children/year (age-adjusted incidence rate, ages 0 to 19 years, between 2007 and 2011)
Peak incidence in children ≤7 years of age
Approximately 1 in 2,000 children born 2009 to 2011 will be diagnosed with a primary malignant CNS tumor by age 14 years.

Risk Factors

Genetics

Brain tumors are not inherited.
About 5% of primary brain tumors may be linked to hereditary genetic syndromes:
- Neurofibromatosis with optic pathway gliomas (NF1) and meningiomas, vestibular schwannomas (NF2)
- Tuberous sclerosis with gliomas and rarely ependymomas
- Li-Fraumeni syndrome with astrocytomas
- von Hippel-Lindau with cerebellar hemangioblastoma
- Turcot syndrome with medulloblastoma

Pathophysiology

Tumors are now classified based on histology and molecular genetic features. The most common are the following:

Diffuse gliomas/other astrocytic tumors
- Arises from glial cells (e.g., astrocytes most common in children)
- ~50% of childhood CNS tumors
- Ranges from low-grade (grade I to II; often in the cerebellum or optic pathway) to high-grade (grade III to IV; in the cerebrum or brainstem)
- Locally recurrent and invasive when high grade
- Molecular alterations distinguish pediatric from adult gliomas.
Embryonal tumors
- Heterogenous group of tumors that arise from malignant embryonic cells
- Comprises ~15% of childhood CNS tumors
- Most common malignant brain tumor in children
- Most common embryonal tumor (60%) is medulloblastoma (cerebellum).
- Predisposition for leptomeningeal dissemination
Ependymoma
- Arises from ependymal cells that line the ventricular system
- 5–8% of childhood CNS tumors
- Most commonly occurs in the 4th ventricle; may arise in the spinal cord
- Locally recurrent and invasive; spinal metastases rare at initial diagnosis
Germ cell tumors
- Derived from totipotent germ cells
- 3–5% of childhood CNS tumors
- Majority are located in the pineal or suprasellar region.
Atypical teratoid/rhabdoid tumor
- Now classified under embryonal tumors
- <3% of childhood CNS tumors
- Majority arise in children <5 years of age.
- Propensity to arise in the posterior fossa with frequent leptomeningeal dissemination; reported in association with malignant rhabdoid tumors of the kidney
Neuronal and mixed neuronal-glial tumors: 6% of childhood CNS tumors
Craniopharyngioma: 3–5% of childhood CNS tumors
Choroid plexus tumors (papilloma and carcinoma)
Meningioma and hemangioblastoma, rare in children

Etiology

No specific causative agents are known, but there is an association with exposure to ionizing radiation, other malignancies, familial/heritable diseases, immunosuppression/immunodeficiency (CNS lymphoma).
Molecular markers and variants of individual tumor types are being identified.

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