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The Central Nervous System Primitive Neuroectodermal Tumor, 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|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 or partially differentiated .<ref name=":0" /> Those cells are usually [[Neuroepithelial cell|neuroepithelial cells]],<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|neurons]].<ref name=":3">{{Cite journal|last=Nelesen|first=Richard A|date=2000-03|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|spinal cord]] and [[cerebrum]] and can have multiple sites of origins, with a high probability of [[metastasis]] through [[Cerebrospinal fluid|cerebrospinal fluid]] (CSF).<ref name=":0" /><ref name=":1" />
PNETsPNET havehas five subtypes of tumors: [[neuroblastoma]], [[ganglioneuroblastoma]], [[medulloepithelioma]], ependymoblastoma, and not otherwise specified PNET.<ref name=":0" /> TheyIt areis similar to medulloblastomas[[medulloblastoma]] in regards toregarding histology but different inregarding regardsgenetic tofactors site ofand tumor and genetic factorssite. It is a rare tumordisease occurring mostly among children, <ref name=":0" /><ref name=":1" /> accounting for 1.9 to 7% of childhood brain tumors.<ref name=":1" /> Its diagnosis can be acquired through magnetic[[Magnetic resonance imaging]] (MRI) orand [[CT scan|computed tomography]] (CT) are used to diagnose PNETs.<ref name=":1" /> ThereEven isnthough an universal treatment plan hasn't abeen standardizedstablished procedureyet, but common strategies involve [[chemotherapy]] and [[Radiation therapy|radiotherapy]] for individuals older than 3 years of age.<ref name=":0" /><ref name=":1" /> Their effectivenessefficacy, however, is still controversial.<ref name=":1" /> Surgery iscan be used to remove mass affected by the tumorous cells.<ref name=":1" /> The prognosis of the disease is more positive for adults than for children, who have a higher probability of developinghaving sequelae sidefrom effectsthe tumor.<ref name=":0" /><ref name=":1" />
== Classification ==
[[File:Medulloepithelioma Histology.jpg|thumb|Histology of [[Medulloepithelioma]]]]
The [[World Health Organization]] has classified the Central Nervous System Primitive Neuroectodermal Tumor into 5 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|Neuroblastomas]] are PNETS that involve the process of cell differentiation into neurons,<ref name=":0" /><ref name=":1" /> while [[Ganglioneuroblastoma|ganglioneuroblastomas]] are PNETs that involve [[Ganglion cell|ganglion cells]].<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|central nervous system]]. <ref name=":0" /><ref name=":1" /><ref name=":2" /> [[Medulloepithelioma|Medulloepitheliomas]] 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|medulloepitheliomas]], ependymoblastomas, and variants of PNETs with presence of rosettes and with no well defined classification.<ref name=":2" />
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