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Oligoastrocytoma, NOS is an uncommon neuropathology tumour that is no longer a distinct entity.[1]


  • Mixed tumour by definition.
  • After IDH-1/2 mutation screening and LOH 1p/19q analysis almost all tumors are either classified as oligodendroglioma or astrocytoma.[1]
  • The NOS category is reserved for cases without genetic testing.[2]

Two types exist:

  • Oligoastrocytoma, NOS (Grade II WHO; ICD-O: 9382/3)
  • Anaplastic Oligoastrocytoma, NOS (Grade III WHO; ICD-O: 9382/3)



  • Astrocytoma-like and oligodendroglioma-like:
    1. Oligodendroglioma-like cells = round nucleus, peri-nuclear clearing.
    2. Astrocytoma-like cells = non-ovoid/elongated nucleus.



  • Oligodendroglioma-like cells: MAP2 +ve (cytoplasm).
  • Astrocytoma-like cells: GFAP +ve (cytoplasm, nuclear membrane).


  • Ki-67 3-10%.
  • ATRX loss (in cases without LOH1p/19q).
  • IDH-1 +ve. (85%).

See also


  1. 1.0 1.1 Sahm, F.; Reuss, D.; Koelsche, C.; Capper, D.; Schittenhelm, J.; Heim, S.; Jones, DT.; Pfister, SM. et al. (Oct 2014). "Farewell to oligoastrocytoma: in situ molecular genetics favor classification as either oligodendroglioma or astrocytoma.". Acta Neuropathol 128 (4): 551-9. doi:10.1007/s00401-014-1326-7. PMID 25143301.
  2. Louis, DN.; Perry, A.; Reifenberger, G.; von Deimling, A.; Figarella-Branger, D.; Cavenee, WK.; Ohgaki, H.; Wiestler, OD. et al. (Jun 2016). "The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary.". Acta Neuropathol 131 (6): 803-20. doi:10.1007/s00401-016-1545-1. PMID 27157931.