Central nervous system primitive neuroectodermal tumor: Difference between revisions

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A '''central nervous system primitive neuroectodermal tumor''', often abbreviated as '''PNET''', '''supratentorial PNET''', or '''CNS-PNET''',<ref name=":0">{{Cite journalbook|date=2015|editor-last=Karajannis|editor-first=Matthias A.|editor2-last=Zagzag|editor2-first=David|title=Molecular Pathology of Nervous System Tumors|journal=Molecular Pathology Library|volume=8|doi=10.1007/978-1-4939-1830-0|issn=1935-987X|isbn=978-1-4939-1829-4 |title=Molecular Pathology of Nervous System Tumors |series=Molecular Pathology Library }}</ref> is one of the 3 types of embryonal central nervous system tumors defined by the [[World Health Organization]] ([[medulloblastoma]], [[atypical teratoid rhabdoid tumor]], and PNET).<ref name=":1">{{Cite journalbook|date=2014|editor-last=Hayat|editor-first=M.A.|title=Tumors of the Central Nervous System, Volume 13|journal=Tumors of the Central Nervous System|volume=13|doi=10.1007/978-94-007-7602-9|issn=2215-096X|isbn=978-94-007-7601-2 |title=Tumors of the Central Nervous System, Volume 13 }}</ref> It is considered an embryonal tumor because it arises from cells partially differentiated or still undifferentiated from birth.<ref name=":0" /> Those cells are usually [[neuroepithelial cell]]s,<ref name=":0" /><ref name=":1" /><ref name=":2">{{Citation|last=Fuller|first=Christine E.|chapter=Oligodendroglial Tumors|date=2009-10-23|pages=39–46|publisher=Springer New York|isbn=9781441910615|doi=10.1007/978-1-4419-1062-2_4|title=Atlas of Pediatric Brain Tumors}}</ref> stem cells destined to turn into [[glia]] or [[neuron]]s.<ref name=":3">{{Cite journal|last=Nelesen|first=Richard A|date=March 2000|title= Biological Psychology: An Introduction to Behavioral, Cognitive, and Clinical Neuroscience, 2nd edition. Mark R. Rosenweig, Arnold L. Leiman, and [[Marc Breedlove|S. Marc Breedlove]], Sinauer Associates, Inc., Sunderland MA, 1999. 561+92 pp. ISBN 0-87893-791-9|journal=Biological Psychology|volume=52|issue=2|pages=185–186|doi=10.1016/s0301-0511(99)00025-3|s2cid=54349873|issn=0301-0511}}</ref> It can occur anywhere within the [[spinal cord]] and [[cerebrum]] and can have multiple sites of origins, with a high probability of [[metastasis]] through [[cerebrospinal fluid]] (CSF).<ref name=":0" /><ref name=":1" />

PNET has five subtypes of tumors: [[neuroblastoma]], [[ganglioneuroblastoma]], [[medulloepithelioma]], ependymoblastoma, and not otherwise specified PNET.<ref name=":0" /> It is similar to [[medulloblastoma]] regarding histology but different regarding genetic factors and tumor site. It is a rare disease occurring mostly among children,<ref name=":0" /><ref name=":1" /> accounting for 1.9 to 7% of childhood brain tumors.<ref name=":1" /> Symptoms involve emotional, visual, motor, and speech defects.<ref name=":1" /> [[Magnetic resonance imaging]] (MRI) and [[CT scan|computed tomography]] (CT) are used to diagnose PNETs.<ref name=":1" /> Even though a universal treatment plan hasn't been stablished yet, common strategies involve [[chemotherapy]] and [[Radiation therapy|radiotherapy]] for individuals older than 3 years of age.<ref name=":0" /><ref name=":1" /> Their efficacy, however, is still controversial.<ref name=":1" /> Surgery can be used to remove mass affected by tumorous cells.<ref name=":1" /> The prognosis of the disease is more positive for adults than for children, who have a higher probability of having sequelae from the tumor.<ref name=":0" /><ref name=":1" />

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[[File:Ependymoblastomatous Rosette.jpg|thumb|Rosettes in Ependymoblastoma histology]]

Further classification types have come up but not yet approved by the [[World Health Organization]].<ref name=":0" /> The term "embryonal tumor with abundant neuropil and true rosettes", or ETANTR, has been proposed as a sixth subtype of PNET.<ref name=":0" /> However, the still unofficial term "embryonal tumor with multilayered rosettes" (ETMR) has been more frequently used and encompasses ETANTRs, [[medulloepithelioma]]s, ependymoblastomas, and variants of PNETs with presence of rosettes and with no well defined classification.<ref name=":2" />

=== PNET vs. medulloblastoma ===

The differentiation between primitive neuroectodermal tumor in the central nervous system and [[medulloblastoma]] is recent.<ref name=":0" /><ref name=":1" /> According to the [[World Health Organization]], both tumors have the same histology but primitive neuroectodermal tumors occur outside the [[cerebellum]].<ref name=":1" /> Moreover, it has been documented that both have different genetic expression and mutations.<ref name=":0" /><ref name=":1" /> Another essential difference between them is the ___location of their respective blood vessels within the brain.<ref name=":1" /> It has also been theorized that PNETs influence mainly [[glia]] cells while [[medulloblastoma]]s influence mainly [[Neuron|neural]] behavior, however such theory hasn't been confirmed yet.<ref name=":0" /> [[Medulloblastoma]]s are more frequent than PNETs, representing 10% of all child deaths caused by cancer.<ref name=":1" /> They also present better prognosis: children affected by [[medulloblastoma]] reach the 5 year survival mark in 70-80% of cases, while children affected by PNET reach the 5 year survival mark in less than 50% of cases.<ref name=":0" />

== Risk factors ==

The rate of PNETs in not correlated with sex, but it shows a correlation with age.<ref name=":0" /> Most cases occur in children around 5 years of age, having a very low frequency in adults.<ref name=":0" /> Regarding genetic mutations, a specific type of gene alteration that directly leads to this tumor hasn't been defined yet.<ref name=":0" /> However, a positive correlation between individuals with [[Li–Fraumeni syndrome|Li-Fraumeni syndrome]] with a mutation in the [[P53|gene ''p53'']] and PNET has been reported.<ref name=":1" /> A significant number of individuals with mutations on the [[Retinoblastoma protein|''rb'' tumor suppressor gene]] have also developed the tumor.<ref name=":1" /> Such gene encodes for the protein Rb responsible for stopping the cell cycle at the [[G1 phase]].<ref name=":4">{{Cite journal|last=Baker|first=Henry V|date=June 2003|title= ''Essential Genetics: A Genomics Perspective'' . ''Third Edition. By '' Daniel L Hartl '' and '' , Elizabeth W Jones. ''Sudbury (Massachusetts): Jones and Bartlett Publishers'' . $78.95 (paperPaper). xxviXxvi + 613 p; ill.; index. ISBN: 0–7637–1852–1. 2002.|isbn=0-7637-1852-1|journal=The Quarterly Review of Biology|volume=78|issue=2|pages=[https://archive.org/details/essentialgenetic0000hart/page/225 225–226]|doi=10.1086/377959|issn=0033-5770|url-access=registration|url=https://archive.org/details/essentialgenetic0000hart/page/225}}</ref> Another possible contributing factor are mutations in the [[CREB-binding protein]], whose function includes activating transcription,<ref name=":4" /> but this interaction still need to be studied further.<ref name=":1" /> It has also been presumed that the tumor can arise from cranial irradiation.<ref name=":1" />

== Diagnosis ==