Primitive neuroectodermal tumor
|Primitive neuroectodermal tumor|
|Classification and external resources|
Primitive Neuroectodermal Tumor (PNET) is a malignant (cancerous) neural crest tumor. It is a rare tumor, usually occurring in children and young adults under 25 years of age. The overall 5 year survival rate is about 53%.
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".
PNET belongs to the Ewing family of tumors.
It is classified into two types, based on location in the body: peripheral PNET and CNS PNET.
The 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."
PNET of the CNS
PNET of the CNS generally refer to supratentorial PNETs.
- In the past medulloblastomas were considered PNETs; however, they are genetically, transcriptionally and clinically distinct. As such, "infratentorial" PNETs are now referred to as medulloblastoma.
- Pineoblastomas are embryonal tumours originating in the pineal gland and are likely distinct from supratentorial PNETs.
Patients diagnosed with a medulloblastoma or PNET are 50 times more likely to die than a matched member of the general population. The 5-year relative survival estimates (based on data from 2001–2006) are 64% in children (1–9 years), 35% in adults (20–25 years), and two known survivors over the age of 25 (Brian Fitzpatrick) aged 34 in 2002. In 2007 a PNET was discovered in the oldest known patient(Tim Young 41 years of age) in Atlanta wrapped around the spinal cord in the C4 cervical area for the first time. A sample was removed by Neurosurgeon Dr David Disch, and the spinal cord was compromised to avoid the tumor from entering the spinal fluids. The procedure caused right side hemiparesis but no other effects. Oncologist Dr Ron Steis(Atlanta Cancer Care) and a global team administered 15 rounds of 5 types of chemo, followed up by 8 weeks of trilogy radiation, and 22 additional rounds of chemo until the patient was cleared. As of March 2014 Mr Young is still the oldest known survivor of PNET.
Using 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. 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.
- "primitive neuroectodermal tumor" at Dorland's Medical Dictionary
- Smoll, N. R. (2012). "Relative survival of childhood and adult medulloblastomas and primitive neuroectodermal tumors (PNETs)". Cancer 118 (5): 1313–1322. doi:10.1002/cncr.26387. PMID 21837678.
- Kumar, Vinay; Fausto, Nelso; Abbas, Abul (2004) Robbins & Cotran Pathologic Basis of Disease (7th ed.). Saunders. Page 1301. ISBN 0-7216-0187-1.
- Eibl RH, Kleihues P, Jat PS, Wiestler OD (March 1994). "A model for primitive neuroectodermal tumors in transgenic neural transplants harboring the SV40 large T antigen". Am. J. Pathol. 144 (3): 556–64. PMC 1887088. PMID 8129041.
- Ohgaki H, Eibl RH, Wiestler OD, Yasargil MG, Newcomb EW, Kleihues P (November 1991). "p53 mutations in nonastrocytic human brain tumors". Cancer Res. 51 (22): 6202–5. PMID 1933879.