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Medulloblastoma accounts for 15-20% of all pediatric brain tumors.

First described in 1925 by Bailey and Cushing.

About 250 to 500 children are diagnosed with medulloblastoma each year in the United States.  In children up to 15 years of age the incidence is 0.5 per 100,000.

The WHO reclassified brain tumors in 2016

Embryonal tumors are mitotically active, small round blue tumor cells and the term primitive neuroectodermal tumor was removed from the newest WHO classification.

Medulloblastoma is an infratentorial embryonal tumor:

  • Malignant, invasive embryonal tumor.
  • By definition, a medulloblastoma is an embryonal tumor arising in the posterior fossa and is infratentorial - this means that this tumor arises below the tentorium (see diagram below where S is supratentorial, I is infratentorial and T is the tentorium).
  • In children, medulloblastomas generally arise in the midline of the cerebellum.

Most common between the ages of 4 and 6:

  • 20% of patients less than 2 years old
  • 80% less than 15 years old
  • very unusual in adults, but can occur
  • Slight male predominance (male to female ratio of 3:2)
  • No racial predisposition to this tumor


Summary of Facts about the Incidence of Medulloblastoma:

Proportion of pediatric brain tumors


Common age of onset


% of patients less than 2 years old


% of patients less than 15 years old


Gender bias

3:2 male predominance

Racial bias




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