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Primitive neuroectodermal tumor (PNET) is a neural crest tumor.[1] It is a rare tumor, usually occurring in children under 10 years old. It has a survival rate of less than 40%.[2] It gets its name because the majority of the cells in the tumor are derived from neuroectoderm, but have not developed and differentiated in the way a normal neuron would, and so the cells appear "primitive". For example, medulloblastoma is now known to derive from neural stem cell precursors, but because of the unusual appearance, for years it was thought to be a glioma. PNET belongs to the Ewing family of tumors. Ependymoblastoma is a synonym for PNET[3]
[edit] ClassificationIt is classified into two types, based on location in the body: peripheral PNET and CNS PNET. It is also possible to add a third category, involving tumors of the autonomic nervous system, such as neuroblastoma.[4][5] [edit] Peripheral PNETThe peripheral PNET (pPNET) is now thought to be virtually identical to Ewing sarcoma: "Current evidence indicates that both Ewing's sarcoma and PNET have a similar neural phenotype and, because they share an identical chromosome translocation, they should be viewed as the same tumor, differing only in their degree of neural differentiation. Tumors that demonstrate neural differentiation by light microscopy, immunohistochemistry, or electron microscopy have been traditionally labeled PNETs, and those that are undifferentiated by these analyses have been diagnosed as Ewing's sarcoma."[6] [edit] PNET of the CNSPNET of the CNS are grossly divided into supratentorial PNET and infratentorial PNET, the latter being more common.[7]
[edit] ModelUsing gene transfer of SV40 large T-antigen in neuronal precursor cells of rats, a brain tumor model was established. The PNETs were histologically indistinguishable from the human counterparts and have been used to identify new genes involved in human brain tumor carcinogenesis.[8] The model was used to confirm p53 as one of the genes involved in human medulloblastomas, but since only about 10% of the human tumors showed mutations in that gene, the model can be used to identify the other binding partners of SV40 Large T- antigen, other than p53.[9] [edit] See also[edit] References
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