[[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]], [[Primitive neuroectodermal tumor|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 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" /> [[Primitive neuroectodermal tumor|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]], [[Primitive neuroectodermal tumor|ependymoblastomas]], and variants of PNETs with presence of rosettes and with no well defined classification.<ref name=":2" />
