Central nervous system primitive neuroectodermal tumor: Difference between revisions

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{{Orphan|date=March 2019}}

[[File:PNET.jpg|thumb|Primitive Neuroectodermal Tumor of the [[Central nervous system|Central Nervous System]] in a 5-year-old]]

[[File:PNET.jpg|thumb|Primitive Neuroectodermal Tumor of the [[Central nervous system|Central Nervous System]] in a 5-year-old]]TheA '''Centralcentral Nervousnervous Systemsystem Primitiveprimitive Neuroectodermalneuroectodermal Tumortumor''', often abbreviated as '''PNET''', '''supratentorial PNET''', or '''CNS-PNET''',<ref name=":0">{{Cite journal|date=2015|editor-last=Karajannis|editor-first=Matthias A.|editor2-last=Zagzag|editor2-first=David|title=Molecular Pathology of Nervous System Tumors|url=http://dx.doi.org/10.1007/978-1-4939-1830-0|journal=Molecular Pathology Library|doi=10.1007/978-1-4939-1830-0|issn=1935-987X}}</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 journal|date=2014|editor-last=Hayat|editor-first=M.A.|title=Tumors of the Central Nervous System, Volume 13|url=http://dx.doi.org/10.1007/978-94-007-7602-9|journal=Tumors of the Central Nervous System|doi=10.1007/978-94-007-7602-9|issn=2215-096X}}</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.|title=Oligodendroglial Tumors|date=2009-10-23|url=http://dx.doi.org/10.1007/978-1-4419-1062-2_4|work=Atlas of Pediatric Brain Tumors|pages=39–46|publisher=Springer New York|isbn=9781441910615|access-date=2019-02-24}}</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 S. Marc Breedlove, Sinauer Associates, Inc., Sunderland MA, 1999. 561+92 pp. ISBN 0-87893-791-9|url=http://dx.doi.org/10.1016/s0301-0511(99)00025-3|journal=Biological Psychology|volume=52|issue=2|pages=185–186|doi=10.1016/s0301-0511(99)00025-3|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 an 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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== Classification ==

[[File:Medulloepithelioma Histology.jpg|thumb|Histology of [[Medulloepithelioma]]]]

The [[World Health Organization]] has classified the Centralcentral Nervousnervous Systemsystem Primitiveprimitive Neuroectodermalneuroectodermal Tumortumors into 5five subtypes: [[neuroblastoma]], [[ganglioneuroblastoma]], [[medulloepithelioma]], ependymoblastoma, and not otherwise specified PNET.<ref name=":0" /> The last one encompasses the PNETs with varying characteristics that hasn't been well defined yet.<ref name=":0" /> [[Neuroblastoma]]s are PNETS that involve the process of cell differentiation into neurons,<ref name=":0" /><ref name=":1" /> while [[ganglioneuroblastoma]]s are PNETs that involve [[ganglion cell]]s.<ref name=":0" />

[[Medulloepithelioma]], on the other hand, are tumors involving the constant cell division on the [[epithelium]] tissue where bundle of neuron endings are located.<ref name=":0" /> Such tissue will differentiate into a similar form as the embryonic neural tube, also known as the starting structure of the [[central nervous system]].<ref name=":0" /><ref name=":1" /><ref name=":2" /> [[Medulloepithelioma]]sMedulloepitheliomas also present a pattern known as rosettes, characterized by the arrangement of a bundle of cells into circular shapes and around a center or a neuropil.<ref name=":0" /> Ependymoblastoma also present rosettes as well as a higher density of cells.<ref name=":0" /><ref name=":2" /> It involves the process of differentiation into ependymal cells.<ref name=":1" /><ref name=":2" />

[[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. Medulloblastomamedulloblastoma ===

[Image of rosettes or of histology will be added]

=== 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 Factorsfactors ==

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 (paper). xxvi + 613 p; ill.; index. ISBN: 0–7637–1852–1. 2002.|url=http://dx.doi.org/10.1086/377959|journal=The Quarterly Review of Biology|volume=78|issue=2|pages=225–226|doi=10.1086/377959|issn=0033-5770}}</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" />

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The effect of treatment strategies such as [[chemotherapy]] and [[radiation therapy]] on the prognosis of the disease is still controversial, with studies claiming either their benefits or their ineffectiveness.<ref name=":1" /> The same holds true for the relationship between volume of tumor removed by surgery and survival.<ref name=":1" /> Furthermore, factors such as tumor size, ___location of origin, race, and sex of individual don't show any influence on the outcome of the disease.<ref name=":1" /> However, interactions of some factors such as tumor site, age, and treatment strategy can affect one's prognosis.<ref name=":1" /> For instance, when younger children below the age of 3 suffering from tumors originating in places other than the [[pineal gland]] are treated with [[chemotherapy]], they present better outcomes than those suffering from [[Pineal gland|pineal]] tumors and treated with [[chemotherapy]].<ref name=":1" />

== References ==

{{Reflist}}

[[Category:Nervous system neoplasia]]