DESCRIPTION

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

EPIDEMIOLOGY

• Most common malignant solid neoplasm of childhood
• Most common cause of cancer death in children 0 to 14 years of age
• Slight male predominance in malignant tumors, more common in White children
• Majority arise infratentorially (within cerebellum or brainstem) in children 1 to 14 years of age.
• Majority arise supratentorially in children <1 year of age.

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).
• Claims made about high-power lines and cellular phones causing brain tumors or cancer are unproven.

RISK FACTORS

PATHOPHYSIOLOGY

Brain tumors are classified on the basis of cell origin, histology, and molecular alterations. The most recent update on classification of brain tumors published by the World Health Organization was in 2021. The most common are the following:

• Gliomas/other astrocytic tumors
  • Arises from glial cells (e.g., astrocytes most common in children)
  • Approximately half 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 cerebral hemisphere or midline structures)
  • Locally recurrent and invasive with potential dissemination when high grade
  • Molecular alterations distinguish pediatric from adult gliomas. For example, RAf-mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway is often altered in low-grade glioma. Classic genetic alteration in diffuse midline gliomas is H3K27M mutation.
• Embryonal tumors
  • Heterogenous group of tumors that arise from malignant embryonic cells
  • Comprises ~12% of childhood CNS tumors
  • Medulloblastoma (cerebellum)
    • Most common embryonal tumor (65%)
    • Predisposition for leptomeningeal dissemination
  • Atypical teratoid/rhabdoid tumor
    • ~2% 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
• Ependymoma
  • Arises from ependymal cells that line the ventricular system
  • ~5% of childhood CNS tumors
  • Most commonly occurs in the 4th ventricle; may arise supratentorially or in the spinal cord
  • Locally recurrent and invasive; spinal metastases rare at initial diagnosis
• Germ cell tumors
  • Derived from totipotent germ cells
  • ~3% of childhood CNS tumors
  • Majority are located in the pineal or suprasellar region.
• Neuronal and mixed neuronal-glial tumors: 8% of childhood CNS tumors
• Craniopharyngioma: 3–5% of childhood CNS tumors
• Choroid plexus tumors (papilloma and carcinoma): ~2% of childhood CNS tumors
• Meningioma and hemangioblastoma: rare in children