They contain many rosettes and well-formed glandular structures. CSF dissemination may occur. An entity distinct from adult pilocytic astrocytoma or glioblastoma. It is a rare, distinct tumor of early childhood occurring mainly in the posterior fossa and spinal cord. Has a characteristic histological appearance.
Biological behavior ranges from indolent to aggressive.
A malignant, embryonal childhood tumor located in the cerebellum. A WHO Working Group concluded that definitive evidence does not exist to state that tumors termed PNETs share a common origin. Therefore, it was recommended that the diagnosis of PNET be used for cerebellar medulloblastomas and other indistinguishable neoplasms found in other CNS locations. There may be an embryologic justification for grouping these tumors together with pineoplastoma and ependymoblastoma. The incidence curve reaches a plateau between ages three to eight years, with a peak at age eight, but the tumor has been found in patients of all ages, from newborns to adults in the seventh decade.