Difference between revisions of "Astrocytoma, IDH-mutant"

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* Diffuse astrocytoma,NOS (ICD-O 9400/3) - genetic testing still missing.
* Diffuse astrocytoma,NOS (ICD-O 9400/3) - genetic testing still missing.


==Radiology/Clinic==
==Astrocytoma, IDH mutant grade 2==
* Most common CNS grade 2 WHO glioma in adults (peaks between 30-40 years).
* 10-15% of all [[astrocytoma]]s.
* Usually shows progression to WHO CNS grade 3 sooner or later. <ref>{{Cite journal  | last1 = Louis | first1 = DN. | last2 = Perry | first2 = A. | last3 = Reifenberger | first3 = G. | last4 = von Deimling | first4 = A. | last5 = Figarella-Branger | first5 = D. | last6 = Cavenee | first6 = WK. | last7 = Ohgaki | first7 = H. | last8 = Wiestler | first8 = OD. | last9 = Kleihues | first9 = P. | title = The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. | journal = Acta Neuropathol | volume = 131 | issue = 6 | pages = 803-20 | month = Jun | year = 2016 | doi = 10.1007/s00401-016-1545-1 | PMID = 27157931 }}</ref>
 
==Astrocytoma, IDH mutant grade 3==
* Most common CNS grade 3 WHO glioma in adults (peaks between 40-50 years).
* Approx 5% of all [[glioma]]s.<ref>{{Cite journal  | last1 = Ohgaki | first1 = H. | last2 = Kleihues | first2 = P. | title = Population-based studies on incidence, survival rates, and genetic alterations in astrocytic and oligodendroglial gliomas. | journal = J Neuropathol Exp Neurol | volume = 64 | issue = 6 | pages = 479-89 | month = Jun | year = 2005 | doi =  | PMID = 15977639 }}</ref>
* Usually shows progression to WHO CNS grade 4 sooner or later.
*Overall prognosis is rather poor (average survival 2-3 years).
*Grade 3 tumors share a similiar prognosis to grade 2 IDH-mutant tumors.<ref>{{Cite journal  | last1 = Reuss | first1 = DE. | last2 = Mamatjan | first2 = Y. | last3 = Schrimpf | first3 = D. | last4 = Capper | first4 = D. | last5 = Hovestadt | first5 = V. | last6 = Kratz | first6 = A. | last7 = Sahm | first7 = F. | last8 = Koelsche | first8 = C. | last9 = Korshunov | first9 = A. | title = IDH mutant diffuse and anaplastic astrocytomas have similar age at presentation and little difference in survival: a grading problem for WHO. | journal = Acta Neuropathol | volume = 129 | issue = 6 | pages = 867-73 | month = Jun | year = 2015 | doi = 10.1007/s00401-015-1438-8 | PMID = 25962792 }}</ref>
==Astrocytoma, IDH mutant grade 4==
* Formely called glioblastoma, IDH-mutant or "secondary glioblastoma".
* CDKN2A deletion in grade 2 or grade 3 tumors results in upgrading to CNS WHO grade 4.
 
=Radiology/Clinic=
*Mass effect.
*Mass effect.
*Seizures.
*Seizures.
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*CNS grade 3 and 4: The majority are contrast-enhanching, T2 bright.
*CNS grade 3 and 4: The majority are contrast-enhanching, T2 bright.


==Macroscopy==
=Macroscopy=
*No clear demarcation from white matter.
*No clear demarcation from white matter.
*Softer consistency and opacity.  
*Softer consistency and opacity.  
Line 22: Line 38:
*CNS grade 2 and 3: No necrosis.
*CNS grade 2 and 3: No necrosis.


==Histology==
=Histology=
CNS grade 2 features: <ref name=AFIP2007>{{Ref AFIP2007|34}}</ref>
CNS grade 2 features: <ref name=AFIP2007>{{Ref AFIP2007|34}}</ref>
*Cell density higher than normal brain.
*Cell density higher than normal brain.
Line 55: Line 71:
*Necrosis (less common than in [[glioblastoma]]).
*Necrosis (less common than in [[glioblastoma]]).


==IHC==
=IHC=
*[[GFAP]]+ve.
*[[GFAP]]+ve.
*[[MAP2]]+ve (especially in cell processes).
*[[MAP2]]+ve (especially in cell processes).
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*[[ATRX]] nuclear loss.
*[[ATRX]] nuclear loss.


 
=Molecular=
==Astrocytoma, IDH mutant grade 2==
*IDH1 R132- or IDH2 R172-hotspot mutations are mandatory.
 
*Absence of LOH 1p/19q (otherwise classify tumor as [[oligodendroglioma]], IDH-mutant and 1p/19q codeleted).
* Most common CNS grade 2 WHO glioma in adults (peaks between 30-40 years).
* 10-15% of all [[astrocytoma]]s.
* Usually shows progression to [[glioblastoma]] sooner or later.
 
WHO 2016 categorization combines morphology and genetics into following groups:<ref>{{Cite journal  | last1 = Louis | first1 = DN. | last2 = Perry | first2 = A. | last3 = Reifenberger | first3 = G. | last4 = von Deimling | first4 = A. | last5 = Figarella-Branger | first5 = D. | last6 = Cavenee | first6 = WK. | last7 = Ohgaki | first7 = H. | last8 = Wiestler | first8 = OD. | last9 = Kleihues | first9 = P. | title = The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. | journal = Acta Neuropathol | volume = 131 | issue = 6 | pages = 803-20 | month = Jun | year = 2016 | doi = 10.1007/s00401-016-1545-1 | PMID = 27157931 }}</ref>
*Diffuse astrocytoma, IDH-mutant  ICD-O: 9400/3 - most frequent.
**Gemistocytic astrocytoma, IDH-mutant ICD-O:9411/3
*Diffuse astrocytoma, IDH-wildtype ICD-O: 9400/3
*Diffuse astrocytoma,NOS ICD-O: 9400/3 - genetic data missing.
 
''Note:'' Older terminologies included Fibrillary astrocytoma (ICD-O: 9420/3) and Protoplasmatic astrocytoma (ICD-O:9410/3)<ref name=WHOCNS>{{Ref WHOCNS|25}}</ref> This subtyping is no longer in use. These tumors are now classified according their IDH mutation status.
 
==Astrocytoma, IDH mutant grade 3==
 
* Most common CNS grade 3 WHO glioma in adults (peaks between 40-50 years).
* Approx 5% of all [[glioma]]s.<ref>{{Cite journal  | last1 = Ohgaki | first1 = H. | last2 = Kleihues | first2 = P. | title = Population-based studies on incidence, survival rates, and genetic alterations in astrocytic and oligodendroglial gliomas. | journal = J Neuropathol Exp Neurol | volume = 64 | issue = 6 | pages = 479-89 | month = Jun | year = 2005 | doi =  | PMID = 15977639 }}</ref>
* Usually shows progression to [[glioblastoma]] sooner or later.
 
 
 
 
 
==Molecular==
*IDH1 R132- or IDH2 R172-hotsopt mutations classify the tumors as Diffuse astrocytoma, IDH-mutant.
*Absence of LOH 1p/19q (otherwise classify tumor as oligodendroglioma).
*Tp53 mutations in approx. 60% (80-90% in gemistocytic, 50% in fibrillary types).
*Tp53 mutations in approx. 60% (80-90% in gemistocytic, 50% in fibrillary types).
*MGMT promotor methylated in approx. 50%.
*MGMT promotor methylated in approx. 50%.
*CDKN2A/B homozygous deletion in IDH mutant diffuse astrocytoma has unfavourable prognosis.<ref>{{Cite journal  | last1 = Shirahata | first1 = M. | last2 = Ono | first2 = T. | last3 = Stichel | first3 = D. | last4 = Schrimpf | first4 = D. | last5 = Reuss | first5 = DE. | last6 = Sahm | first6 = F. | last7 = Koelsche | first7 = C. | last8 = Wefers | first8 = A. | last9 = Reinhardt | first9 = A. | title = Novel, improved grading system(s) for IDH-mutant astrocytic gliomas. | journal = Acta Neuropathol | volume = 136 | issue = 1 | pages = 153-166 | month = Jul | year = 2018 | doi = 10.1007/s00401-018-1849-4 | PMID = 29687258 }}</ref><ref>{{Cite journal  | last1 = Aoki | first1 = K. | last2 = Nakamura | first2 = H. | last3 = Suzuki | first3 = H. | last4 = Matsuo | first4 = K. | last5 = Kataoka | first5 = K. | last6 = Shimamura | first6 = T. | last7 = Motomura | first7 = K. | last8 = Ohka | first8 = F. | last9 = Shiina | first9 = S. | title = Prognostic relevance of genetic alterations in diffuse lower-grade gliomas. | journal = Neuro Oncol | volume = 20 | issue = 1 | pages = 66-77 | month = 01 | year = 2018 | doi = 10.1093/neuonc/nox132 | PMID = 29016839 }}</ref>
*CDKN2A/B homozygous deletion results in CNS grade 4<ref>{{Cite journal  | last1 = Shirahata | first1 = M. | last2 = Ono | first2 = T. | last3 = Stichel | first3 = D. | last4 = Schrimpf | first4 = D. | last5 = Reuss | first5 = DE. | last6 = Sahm | first6 = F. | last7 = Koelsche | first7 = C. | last8 = Wefers | first8 = A. | last9 = Reinhardt | first9 = A. | title = Novel, improved grading system(s) for IDH-mutant astrocytic gliomas. | journal = Acta Neuropathol | volume = 136 | issue = 1 | pages = 153-166 | month = Jul | year = 2018 | doi = 10.1007/s00401-018-1849-4 | PMID = 29687258 }}</ref><ref>{{Cite journal  | last1 = Aoki | first1 = K. | last2 = Nakamura | first2 = H. | last3 = Suzuki | first3 = H. | last4 = Matsuo | first4 = K. | last5 = Kataoka | first5 = K. | last6 = Shimamura | first6 = T. | last7 = Motomura | first7 = K. | last8 = Ohka | first8 = F. | last9 = Shiina | first9 = S. | title = Prognostic relevance of genetic alterations in diffuse lower-grade gliomas. | journal = Neuro Oncol | volume = 20 | issue = 1 | pages = 66-77 | month = 01 | year = 2018 | doi = 10.1093/neuonc/nox132 | PMID = 29016839 }}</ref>
Note:
Note:
*The existence of diffuse astrocytoma, IDH wildtype is challenged.<ref>{{Cite journal  | last1 = Reuss | first1 = DE. | last2 = Kratz | first2 = A. | last3 = Sahm | first3 = F. | last4 = Capper | first4 = D. | last5 = Schrimpf | first5 = D. | last6 = Koelsche | first6 = C. | last7 = Hovestadt | first7 = V. | last8 = Bewerunge-Hudler | first8 = M. | last9 = Jones | first9 = DT. | title = Adult IDH wild type astrocytomas biologically and clinically resolve into other tumor entities. | journal = Acta Neuropathol | volume = 130 | issue = 3 | pages = 407-17 | month = Sep | year = 2015 | doi = 10.1007/s00401-015-1454-8 | PMID = 26087904 }}</ref>
*The existence of diffuse astrocytoma, IDH wildtype is challenged.<ref>{{Cite journal  | last1 = Reuss | first1 = DE. | last2 = Kratz | first2 = A. | last3 = Sahm | first3 = F. | last4 = Capper | first4 = D. | last5 = Schrimpf | first5 = D. | last6 = Koelsche | first6 = C. | last7 = Hovestadt | first7 = V. | last8 = Bewerunge-Hudler | first8 = M. | last9 = Jones | first9 = DT. | title = Adult IDH wild type astrocytomas biologically and clinically resolve into other tumor entities. | journal = Acta Neuropathol | volume = 130 | issue = 3 | pages = 407-17 | month = Sep | year = 2015 | doi = 10.1007/s00401-015-1454-8 | PMID = 26087904 }}</ref>
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***Glial morphology can be astrocytic or oligodendrocytic.
***Glial morphology can be astrocytic or oligodendrocytic.


==Molecular==
*TERT promotor mutations in 20-25%<ref>{{Cite journal  | last1 = Lee | first1 = Y. | last2 = Koh | first2 = J. | last3 = Kim | first3 = SI. | last4 = Won | first4 = JK. | last5 = Park | first5 = CK. | last6 = Choi | first6 = SH. | last7 = Park | first7 = SH. | title = The frequency and prognostic effect of TERT promoter mutation in diffuse gliomas. | journal = Acta Neuropathol Commun | volume = 5 | issue = 1 | pages = 62 | month = Aug | year = 2017 | doi = 10.1186/s40478-017-0465-1 | PMID = 28851427 }}</ref><ref>{{Cite journal  | last1 = Koelsche | first1 = C. | last2 = Sahm | first2 = F. | last3 = Capper | first3 = D. | last4 = Reuss | first4 = D. | last5 = Sturm | first5 = D. | last6 = Jones | first6 = DT. | last7 = Kool | first7 = M. | last8 = Northcott | first8 = PA. | last9 = Wiestler | first9 = B. | title = Distribution of TERT promoter mutations in pediatric and adult tumors of the nervous system. | journal = Acta Neuropathol | volume = 126 | issue = 6 | pages = 907-15 | month = Dec | year = 2013 | doi = 10.1007/s00401-013-1195-5 | PMID = 24154961 }}</ref>
*Approximately 80 % of IDH wildtype astrocytomas in fact represent underdiagnosed GBM.<ref>{{Cite journal  | last1 = Reuss | first1 = DE. | last2 = Kratz | first2 = A. | last3 = Sahm | first3 = F. | last4 = Capper | first4 = D. | last5 = Schrimpf | first5 = D. | last6 = Koelsche | first6 = C. | last7 = Hovestadt | first7 = V. | last8 = Bewerunge-Hudler | first8 = M. | last9 = Jones | first9 = DT. | title = Adult IDH wild type astrocytomas biologically and clinically resolve into other tumor entities. | journal = Acta Neuropathol | volume = 130 | issue = 3 | pages = 407-17 | month = Sep | year = 2015 | doi = 10.1007/s00401-015-1454-8 | PMID = 26087904 }}</ref>


<gallery>
<gallery>
Line 119: Line 113:
File:Neuropathology case II 02.jpg | Astrocytoma, protoplasmatic type (WC/jensflorian)
File:Neuropathology case II 02.jpg | Astrocytoma, protoplasmatic type (WC/jensflorian)
File:Gemistocytic astrocytoma.jpg | Gemistocytic astrocytoma (WC/jensflorian)
File:Gemistocytic astrocytoma.jpg | Gemistocytic astrocytoma (WC/jensflorian)
File:Mitoses_astro_III.jpg | Marked mitotic activity in anaplastic astrocytoma (WC/jensflorian).
File:405551M-ANAPLASTIC_ASTROCYTOMA.jpg | Marked nuclear pleomorphism (AFIP).
</gallery>
</gallery>


Line 133: Line 129:
For CNS grade 4 tumours:
For CNS grade 4 tumours:
*[[Glioblastoma]] - vascular proliferations and / or necrosis.
*[[Glioblastoma]] - vascular proliferations and / or necrosis.
WHO 2016 categorization combines morphology and genetics into following groups:<ref>{{Cite journal  | last1 = Louis | first1 = DN. | last2 = Perry | first2 = A. | last3 = Reifenberger | first3 = G. | last4 = von Deimling | first4 = A. | last5 = Figarella-Branger | first5 = D. | last6 = Cavenee | first6 = WK. | last7 = Ohgaki | first7 = H. | last8 = Wiestler | first8 = OD. | last9 = Kleihues | first9 = P. | title = The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. | journal = Acta Neuropathol | volume = 131 | issue = 6 | pages = 803-20 | month = Jun | year = 2016 | doi = 10.1007/s00401-016-1545-1 | PMID = 27157931 }}</ref>
*Anaplastic astrocytoma, IDH-mutant  (ICD-O: 9401/3).
*Anaplastic astrocytoma, IDH-wildtype (ICD-O: 9401/3).
*Anaplastic astrocytoma,NOS (ICD-O: 9401/3) - genetic data missing.
==Prognosis==
*Overall prognosis is rather poor (average survival 2-3 years).
*IDH-mutant tumors share a similiar prognosis to grade II IDH-mutant tumors.<ref>{{Cite journal  | last1 = Reuss | first1 = DE. | last2 = Mamatjan | first2 = Y. | last3 = Schrimpf | first3 = D. | last4 = Capper | first4 = D. | last5 = Hovestadt | first5 = V. | last6 = Kratz | first6 = A. | last7 = Sahm | first7 = F. | last8 = Koelsche | first8 = C. | last9 = Korshunov | first9 = A. | title = IDH mutant diffuse and anaplastic astrocytomas have similar age at presentation and little difference in survival: a grading problem for WHO. | journal = Acta Neuropathol | volume = 129 | issue = 6 | pages = 867-73 | month = Jun | year = 2015 | doi = 10.1007/s00401-015-1438-8 | PMID = 25962792 }}</ref>
*Anaplastic astrocytoma, IDH-wildtype perform worse than glioblastoma, IDH-mutant despite grading differences.<ref>{{Cite journal  | last1 = Hartmann | first1 = C. | last2 = Hentschel | first2 = B. | last3 = Wick | first3 = W. | last4 = Capper | first4 = D. | last5 = Felsberg | first5 = J. | last6 = Simon | first6 = M. | last7 = Westphal | first7 = M. | last8 = Schackert | first8 = G. | last9 = Meyermann | first9 = R. | title = Patients with IDH1 wild type anaplastic astrocytomas exhibit worse prognosis than IDH1-mutated glioblastomas, and IDH1 mutation status accounts for the unfavorable prognostic effect of higher age: implications for classification of gliomas. | journal = Acta Neuropathol | volume = 120 | issue = 6 | pages = 707-18 | month = Dec | year = 2010 | doi = 10.1007/s00401-010-0781-z | PMID = 21088844 }}</ref>
<gallery>
File:Mitoses_astro_III.jpg | Marked mitotic activity in anaplastic astrocytoma (WC/jensflorian).
File:405551M-ANAPLASTIC_ASTROCYTOMA.jpg | Marked nuclear pleomorphism (AFIP).
</gallery>
==Molecular==
*TERT promotor mutations in 20-25%<ref>{{Cite journal  | last1 = Lee | first1 = Y. | last2 = Koh | first2 = J. | last3 = Kim | first3 = SI. | last4 = Won | first4 = JK. | last5 = Park | first5 = CK. | last6 = Choi | first6 = SH. | last7 = Park | first7 = SH. | title = The frequency and prognostic effect of TERT promoter mutation in diffuse gliomas. | journal = Acta Neuropathol Commun | volume = 5 | issue = 1 | pages = 62 | month = Aug | year = 2017 | doi = 10.1186/s40478-017-0465-1 | PMID = 28851427 }}</ref><ref>{{Cite journal  | last1 = Koelsche | first1 = C. | last2 = Sahm | first2 = F. | last3 = Capper | first3 = D. | last4 = Reuss | first4 = D. | last5 = Sturm | first5 = D. | last6 = Jones | first6 = DT. | last7 = Kool | first7 = M. | last8 = Northcott | first8 = PA. | last9 = Wiestler | first9 = B. | title = Distribution of TERT promoter mutations in pediatric and adult tumors of the nervous system. | journal = Acta Neuropathol | volume = 126 | issue = 6 | pages = 907-15 | month = Dec | year = 2013 | doi = 10.1007/s00401-013-1195-5 | PMID = 24154961 }}</ref>
*Approximately 80 % of IDH wildtype astrocytomas in fact represent underdiagnosed GBM.<ref>{{Cite journal  | last1 = Reuss | first1 = DE. | last2 = Kratz | first2 = A. | last3 = Sahm | first3 = F. | last4 = Capper | first4 = D. | last5 = Schrimpf | first5 = D. | last6 = Koelsche | first6 = C. | last7 = Hovestadt | first7 = V. | last8 = Bewerunge-Hudler | first8 = M. | last9 = Jones | first9 = DT. | title = Adult IDH wild type astrocytomas biologically and clinically resolve into other tumor entities. | journal = Acta Neuropathol | volume = 130 | issue = 3 | pages = 407-17 | month = Sep | year = 2015 | doi = 10.1007/s00401-015-1454-8 | PMID = 26087904 }}</ref>


==Outdated terminologies==
==Outdated terminologies==
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*Gemistocytic astrocytoma
*Gemistocytic astrocytoma
*Diffuse astrocytoma, IDH-wildtype
*Diffuse astrocytoma, IDH-wildtype
 
*Glioblastoma; IDH-mutant
 
*Fibrillary astrocytoma (ICD-O: 9420/3)  
''Note:'' Older terminologies included Fibrillary astrocytoma (ICD-O: 9420/3) and Protoplasmatic astrocytoma (ICD-O:9410/3)<ref name=WHOCNS>{{Ref WHOCNS|25}}</ref> This subtyping is no longer in use. These tumors are now classified according their IDH mutation status.
*Protoplasmatic astrocytoma (ICD-O:9410/3)


=See also=
=See also=

Revision as of 13:05, 6 April 2022

Astrocytoma, IDH-mutant is a diffusely-growing, infiltrating astrocytoma of the adult occurring in the CNS white matter. IDH1 codon 132 or IDH2 codon 172 mutations is mandatory for diagnosis and are frequently associated with ATRX and TP53 mutations.

General

The current WHO classification recognizes three tumour grades:

  • Astrocytoma, IDH mutant grade 2 (ICD-O: 9400/3)
  • Astrocytoma, IDH mutant grade 3 (ICD-O: 9401/3)
  • Astrocytoma, IDH mutant grade 4 (ICD-O: 9445/3)
  • Diffuse astrocytoma,NOS (ICD-O 9400/3) - genetic testing still missing.

Astrocytoma, IDH mutant grade 2

  • Most common CNS grade 2 WHO glioma in adults (peaks between 30-40 years).
  • 10-15% of all astrocytomas.
  • Usually shows progression to WHO CNS grade 3 sooner or later. [1]

Astrocytoma, IDH mutant grade 3

  • Most common CNS grade 3 WHO glioma in adults (peaks between 40-50 years).
  • Approx 5% of all gliomas.[2]
  • Usually shows progression to WHO CNS grade 4 sooner or later.
  • Overall prognosis is rather poor (average survival 2-3 years).
  • Grade 3 tumors share a similiar prognosis to grade 2 IDH-mutant tumors.[3]

Astrocytoma, IDH mutant grade 4

  • Formely called glioblastoma, IDH-mutant or "secondary glioblastoma".
  • CDKN2A deletion in grade 2 or grade 3 tumors results in upgrading to CNS WHO grade 4.

Radiology/Clinic

  • Mass effect.
  • Seizures.
  • Neurologic decifit.
  • CNS grade 2: Usually not contrast-enhanching, T2 bright.
  • CNS grade 3 and 4: The majority are contrast-enhanching, T2 bright.

Macroscopy

  • No clear demarcation from white matter.
  • Softer consistency and opacity.
  • May contain larger cysts
  • Invaded structures may appear enlarged.
  • CNS grade 2 and 3: No necrosis.

Histology

CNS grade 2 features: [4]

  • Cell density higher than normal brain.
  • Mild to moderate nuclear pleomorphism.
    • Monotony of atypical nuclei and irregular distribution indicates neoplasm.
    • "naked nuclei" without recognizeable processes.
    • No prominent nucleolus.
  • Cytoplasm highly variable (even within the same tumour).
    • In normal CNS the cytoplasm blends within the neuropil.
  • Mitoses absent or very rare.
  • Microcystic spaces of the background (none to extensive).
  • Lymphocytic cuffing (mostly in gemistocytic type)
  • Abent to few rosenthal fibers.

CNS grade 3 features: [4]

  • Increased cellularity (compared to CNS grade 2).
  • Mitoses present (a single mitosis in a small specimen indicates a high-grade tumor).
    • Specimens with low cellularity but plenty of mitoses are also considered grade 3.
  • Distinct nuclear atypia and pleomorphism.
    • May include multinucleated cells.
  • Cytoplasm highly variable (even within the same tumour).
  • Microcystic spaces of the background (none to extensive).
  • No necrosis, no vascular proliferations.
    • Except radiation necrosis after pretreatment.

CNS grade 4 features:

  • Increased cellularity (compared to CNS grade 2).
  • Mitoses frequently present.
  • Distinct nuclear atypia and pleomorphism.
  • Multinucleated cells.
  • Microvascular proliferation.
  • Necrosis (less common than in glioblastoma).

IHC

  • GFAP+ve.
  • MAP2+ve (especially in cell processes).
  • OLIG2 +ve.
  • Vimentin+ve (often perinuclear).
  • S-100+ve.
  • p53: Nuclear staining in 30% of the tumours (usually few cells).
  • MIB-1: CNS grade 2: 0-5% (mean: 2%); CNS grade 3 usu. 5-10%.
  • IDH-1 (R132H)+ve in 60-70%.
    • 'Note: The mutation-specific antibody does not detect other less common IDH1/2 hotspot mutations.
  • ATRX nuclear loss.

Molecular

  • IDH1 R132- or IDH2 R172-hotspot mutations are mandatory.
  • Absence of LOH 1p/19q (otherwise classify tumor as oligodendroglioma, IDH-mutant and 1p/19q codeleted).
  • Tp53 mutations in approx. 60% (80-90% in gemistocytic, 50% in fibrillary types).
  • MGMT promotor methylated in approx. 50%.
  • CDKN2A/B homozygous deletion results in CNS grade 4[5][6]

Note:

  • The existence of diffuse astrocytoma, IDH wildtype is challenged.[7]
    • Most adult cases show genetic alterations compatible with glioblastoma.[8]
    • Molecular upgrade according to cIMPACT-NOW Update 3 consensus (one of these is sufficient):[9]
      • EGFR amplification
      • Combined whole chromosome 7 gain and whole chromosome 10 loss (+ 7/− 10)
      • TERT promoter mutation
    • Suggested Sign-out:
       Diffuse astrocytic glioma, IDH-wildtype, with molecular features of glioblastoma, WHO grade IV
    • WHO grade II diffuse gliomas IDH-wt/H3-wt in children and adolescents have an indolent clinical behavior and rare anaplastic progression.
      • Most tumors show a BRAFV600E mutation, an FGFR alteration, or a MYB or MYBL1 rearrangement.[10]
      • Glial morphology can be astrocytic or oligodendrocytic.

Molecular

  • TERT promotor mutations in 20-25%[11][12]
  • Approximately 80 % of IDH wildtype astrocytomas in fact represent underdiagnosed GBM.[13]

DDx

For CNS grade 2 tumours:

  • Reactive astrocytosis.
  • Demyelinisation.
  • Grade 3 astrocytoma, IDH mutant - increased mitotic activity.
  • Oligodendroglioma, IDH-mutant and 1p/19q codeleted - esp. protoplasmatic forms. LOH 1p/19q testing required.
  • SEGA - esp. gemistocytic forms.
  • Diffuse glioma, MYB- or MYBL1-altered.

For CNS grade 3 tumours:

For CNS grade 4 tumours:

Outdated terminologies

  • Diffuse astrocytoma
  • Gemistocytic astrocytoma
  • Diffuse astrocytoma, IDH-wildtype
  • Glioblastoma; IDH-mutant
  • Fibrillary astrocytoma (ICD-O: 9420/3)
  • Protoplasmatic astrocytoma (ICD-O:9410/3)

See also

  1. 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.
  2. Ohgaki, H.; Kleihues, P. (Jun 2005). "Population-based studies on incidence, survival rates, and genetic alterations in astrocytic and oligodendroglial gliomas.". J Neuropathol Exp Neurol 64 (6): 479-89. PMID 15977639.
  3. Reuss, DE.; Mamatjan, Y.; Schrimpf, D.; Capper, D.; Hovestadt, V.; Kratz, A.; Sahm, F.; Koelsche, C. et al. (Jun 2015). "IDH mutant diffuse and anaplastic astrocytomas have similar age at presentation and little difference in survival: a grading problem for WHO.". Acta Neuropathol 129 (6): 867-73. doi:10.1007/s00401-015-1438-8. PMID 25962792.
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