Primitive neuroectodermal tumour

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CNS Primitive neuroectodermal tumour, abbreviated CNS-PNET, is an abandoned neuropathology tumour description within in the group of embryonal tumours. The terminology was introduced in 1973 [1] and used in the WHO 2007 classification of CNS tumors. Since 2016 this category has been replaced by the designation other CNS embryonal tumors.

Primitive neuroectodermal tumour
Diagnosis in short

CNS primitive neuroectodermal tumour H&E stain.

Synonyms CNS-PNET
LM DDx small round blue cell tumours
IHC S-100 +ve, Syn +/-ve
Site brain, spinal cord

Prevalence rare - typically in young adults
Prognosis poor (WHO Grade IV)


  • Should not be confused with peripheral primitive neuroectodermal tumour (abbreviated pPNET[2]), AKA Ewing sarcoma.
  • The former category contained a heterogenous group of poorly differentiated WHO grade IV tumours associated with following ICD-O codes:
    • 9473/3 CNS-PNET, NOS.
    • 9500/3 CNS neuroblastoma.
    • 9490/3 CNS ganglioneuroblastoma.
    • 9501/3 Medulloepithelioma.
    • 9392/3 Ependymoblastoma.
  • Mainly children and adolescents.
  • Cerebral hemisphere, brain stem or spinal cord.
  • Cerebrospinal dissemination found in up to 1/3 patients.[3]
  • Very poor prognosis[4]



  • Small round blue cell tumour.
    • Focal differentation into astrocytic, neuronal or ependymal phenotypes possible.
  • May have true rosettes (slit-like/oval).
  • Growth in streams or palisades possible ("spongioneuroblastoma").
  • Vascular endothelial proliferations.
  • Fibrillary background in tumours with advanced neuronal maturation (ganglioneuroblastomas).
  • Variable mitotic activity.

Supratentorial PNET

  • This category of small round- and blue cell tumor was used in the WHO 2007 CNS tumor classification to separate them from medulloblastomas.
  • Tumors are today classified as AT/RT, Pineoblastoma, ETMR, H3F3A-mutated glioblastoma or CNS embryonal tumor, NOS.

CNS neuroblastoma

  • Since WHO 2016 CNS classification this is now a subgroup of Other CNS embryonal tumours.
  • Many CNS neuroblastoma / CNS ganglioneuroblastoma cluster molecularly into a group designated as CNS NB-FOXR2.[5]
  • Usu Olig-2 +ve.
  • Synaptophysin +ve.

CNS ganglioneuroblastoma

Lipomatous medulloblastoma

Melanotic medulloblastoma

  • In WHO CNS 1997 still a distinct tumor.
  • These tumors are now considered a variant of medulloblastoma.


  • Embryonal tumor with primitive neuronal cells and striated muscle component.
  • First description in 1933.[6]
  • Since WHO 2007 CNS tumor classification tumors were classified as medulloblastoma with myogenic differentiation.


  • Neuroepithelial tumor cells arranged papillary, tubular or trabecular.
  • Pseudostratified with PAS-positive membrane.
  • Medulloepithelioma are grouped with ependymoblastomas and ETANTR into embryonal tumors with multilayered rosettes (ETMR).[7]
  • Not the same tumour as the intraocular medulloepithelioma.[8]


  • Often supratentorial, well circumscribed.
  • Multilayered ("ependymoblastous") rosettes.
  • High mitotic and proliferative activity
  • Ependymoblastoma are grouped with medulloepithelioma and ETANTR into embryonal tumors with multilayered rosettes (ETMR).[7]


  • S-100 +ve.
  • INI1 +ve (loss defines tumour as ATRT).
  • LIN28+ve (in ETMR), otherwise -ve. [9]
  • Nestin +ve
  • MAP2 +ve/-ve
  • Vimentin +ve
  • IDH-1 -ve
  • No ATRX loss
  • MIB-1 between 20-80% (usu. 50%)

Molecular genetics

Divergent molecular subgroups are emerging:

  • Loss of 9q / CDKN2A deletions in CNS neuroblastoma[10]
  • Amplification 19q13.42 in ETMR[11]




See also


  1. Hart, MN.; Earle, KM. (Oct 1973). "Primitive neuroectodermal tumors of the brain in children.". Cancer 32 (4): 890-7. PMID 4751919.
  2. PST. 14 February 2011.
  3. Horten, BC.; Rubinstein, LJ. (Dec 1976). "Primary cerebral neuroblastoma. A clinicopathological study of 35 cases.". Brain 99 (4): 735-56. PMID 1030655.
  4. Tulla, M.; Berthold, F.; Graf, N.; Rutkowski, S.; von Schweinitz, D.; Spix, C.; Kaatsch, P. (Sep 2015). "Incidence, Trends, and Survival of Children With Embryonal Tumors.". Pediatrics 136 (3): e623-32. doi:10.1542/peds.2015-0224. PMID 26304823.
  5. Sturm, D.; Orr, BA.; Toprak, UH.; Hovestadt, V.; Jones, DTW.; Capper, D.; Sill, M.; Buchhalter, I. et al. (Feb 2016). "New Brain Tumor Entities Emerge from Molecular Classification of CNS-PNETs.". Cell 164 (5): 1060-1072. doi:10.1016/j.cell.2016.01.015. PMID 26919435.
  6. Brody, BS.; German, WJ. (Oct 1933). "Medulloblastoma of the Cerebellum: A Report of 15 Cases.". Yale J Biol Med 6 (1): 19-29. PMID 21433586.
  7. 7.0 7.1 Horwitz, M.; Dufour, C.; Leblond, P.; Bourdeaut, F.; Faure-Conter, C.; Bertozzi, AI.; Delisle, MB.; Palenzuela, G. et al. (Oct 2015). "Embryonal tumors with multilayered rosettes in children: the SFCE experience.". Childs Nerv Syst. doi:10.1007/s00381-015-2920-2. PMID 26438544.
  8. Korshunov, A.; Jakobiec, FA.; Eberhart, CG.; Hovestadt, V.; Capper, D.; Jones, DT.; Sturm, D.; Stagner, AM. et al. (Jul 2015). "Comparative integrated molecular analysis of intraocular medulloepitheliomas and central nervous system embryonal tumors with multilayered rosettes confirms that they are distinct nosologic entities.". Neuropathology. doi:10.1111/neup.12227. PMID 26183384.
  9. Korshunov, A.; Ryzhova, M.; Jones, DT.; Northcott, PA.; van Sluis, P.; Volckmann, R.; Koster, J.; Versteeg, R. et al. (Dec 2012). "LIN28A immunoreactivity is a potent diagnostic marker of embryonal tumor with multilayered rosettes (ETMR).". Acta Neuropathol 124 (6): 875-81. doi:10.1007/s00401-012-1068-3. PMID 23161096.
  10. Pfister, S.; Remke, M.; Toedt, G.; Werft, W.; Benner, A.; Mendrzyk, F.; Wittmann, A.; Devens, F. et al. (Sep 2007). "Supratentorial primitive neuroectodermal tumors of the central nervous system frequently harbor deletions of the CDKN2A locus and other genomic aberrations distinct from medulloblastomas.". Genes Chromosomes Cancer 46 (9): 839-51. doi:10.1002/gcc.20471. PMID 17592618.
  11. Korshunov, A.; Remke, M.; Gessi, M.; Ryzhova, M.; Hielscher, T.; Witt, H.; Tobias, V.; Buccoliero, AM. et al. (Aug 2010). "Focal genomic amplification at 19q13.42 comprises a powerful diagnostic marker for embryonal tumors with ependymoblastic rosettes.". Acta Neuropathol 120 (2): 253-60. doi:10.1007/s00401-010-0688-8. PMID 20407781.
  12. Buccoliero AM, Castiglione F, Degl'Innocenti DR, et al. (February 2010). "Embryonal tumor with abundant neuropil and true rosettes: morphological, immunohistochemical, ultrastructural and molecular study of a case showing features of medulloepithelioma and areas of mesenchymal and epithelial differentiation". Neuropathology 30 (1): 84–91. doi:10.1111/j.1440-1789.2009.01040.x. PMID 19563506.