Medulloblastoma

Synonyms

• Infratentorial primitive neuroectodermal tumor (PNET)

Primitive neuroectodermal tumor of children occurring in the child”s posterior fossa; see also brain tumors.

Definition

Medulloblastomas are malignant embryonal tumors of the cerebellum, composed of densely packed small cells with round to oval nuclei and scanty cytoplasm with a high tendency to metastasize throughout the CNS. The current World Health Organisation (WHO) classification of “Tumors of the Nervous System”, groups medulloblastomas as Primitive Neuroectodermal Tumor (PNET) and recognizes four variants apart from the classic histological subtype:

• desmoplastic medulloblastoma,

• large cell medulloblastoma,

• medullomyoblastoma,

• melanotic medulloblastoma.

Characteristics

Clinical data

Medulloblastomas are the most common malignant brain tumorsoccurring in childhood, affecting each year approximately six of one million children (<20 years) in the United States. Two age peaks at 3-4 and 8-9 years and a male predominance...