Astroblastoma, MN1-altered

Changed by Frank Gaillard, 15 Jun 2022
Disclosures - updated 9 Jun 2022:
  • Radiopaedia Australia Pty Ltd and Radiopaedia Events Pty Ltd, Director, Founder and CEO (Radiopaedia) (ongoing)
  • Biogen Australia Pty Ltd, Investigator-Initiated Research Grant for CAD software in multiple sclerosis: finished Oct 2021 (past)

Updates to Article Attributes

Body was changed:

Astroblastomas are rare glial tumours usually found in the cerebral hemispheres of young adults and children. 

Terminology

The exact nature of astroblastomas remains to be fully elucidated. Tumours with compatible histological features have a variety of molecular characteristics and overlap with other better-known tumours such as pleomorphic xanthoastrocytomas or ependymomas or diffuse astrocytomas 6,7

The presence of MN1 alterations (a transcriptional coregulator involved in the development of acute myeloid leukemialeukaemia and meningiomas) is now used to define the lesion,  and thus it is now named astroblastoma, MN1-altered and considered circumscribed astrocytic gliomas in the current (5th Edition, 2021) WHO classification of CNS tumours 6.

Epidemiology

They occur at all ages range, ranging from early childhood to the 6th decade but are most commonly seen in children, adolescents, and young adults with a mean age between 10-30 years 2,5. A strong female predilection has been suggested in some reports 5,6

Pathology

Astroblastomas have not yet been given a WHO grade, but do have a range of histological appearance and biological behaviour ranging from relatively indolent (astroblastoma) to aggressive (anaplastic or malignant astroblastoma) 4,5

Macroscopic appearance

They are well-demarcated masses with areas of cystic degeneration and necrosis giving it a bubbly appearance. HaemorrhageHaemorrhages and adjacent brain infiltration are rare.

Microscopic appearance

Astroblastomas have elongated glial cells with abundant eosinophilic cytoplasm and a broad, or “stout”, GFAP positive process extending radially towards a central blood vessel, forming "astroblastic pseudorosettes", reminiscent to the perivascular pseudorosettes of ependymomas, which are a characteristic feature of this tumour. The central vessel tends to be hyalinized. 

Although no agreed-upon criteria have been accepted, anaplastic/malignant histological features include 5

  • increased mitotic activity (>5 mitoses per 10 high-powered fields)
  • high cellularity 
  • anaplastic nuclear features
  • microvascular proliferation
  • palisading necrosis 
  • usually Ki-67 >10%
Immunophenotype

Radiographic features

Astroblastomas are usually fairly sizablesizeable, peripherally located, supratentorial lobulated solid cystic masses with little if any associated vasogenic oedema 1-5. Multiple cysts are common and can give it a bubbly appearance. Calcification is very common and seen in 85% of cases, and usually in a punctate pattern.

MRI

Reported signal characteristics include2:

  • T1: iso- to hypointense
  • T2/FLAIR: heterogeneously hyperintense
    • heterogeneous with a multicystic or bubbly appearance
    • solid components tend to be isointense to grey matter
    • relatively little surrounding oedema compared to size
  • T1 C+ (Gd): heterogeneous enhancement
  • DWI/ADC
    • ​facilitated diffusion in fluid/cystic components
    • intermediate ADC values of the solid component (1190 to 1250 x 10-6  mm2/s) 8

Treatment and prognosis

Surgical resection is the treatment of choice with adjuvant radiation therapy and chemotherapy reserved for high-grade lesions. Recurrence after complete surgical resection of low-grade tumours is uncommon 4

Differential diagnosis

Possible imaging differential considerations include:

  • -<p><strong>Astroblastomas</strong> are rare glial tumours usually found in the cerebral hemispheres of young adults and children. </p><h4>Terminology</h4><p>The exact nature of astroblastomas remains to be fully elucidated. Tumours with compatible histological features have a variety of molecular characteristics and overlap with other better-known tumours such as <a href="/articles/pleomorphic-xanthoastrocytoma">pleomorphic xanthoastrocytomas</a> or <a href="/articles/ependymoma">ependymomas</a> or <a href="/articles/astrocytic-tumours">diffuse astrocytomas</a> <sup>6,7</sup>. </p><p>The presence of MN1 alterations (a transcriptional coregulator involved in the development of acute myeloid leukemia and meningiomas) is now used to define the lesion,  and thus it is now named <strong>astroblastoma, MN1-altered</strong> and considered <a href="/articles/astrocytic-tumours">circumscribed astrocytic gliomas</a> in the current (5th Edition, 2021) <a href="/articles/who-classification-of-cns-tumours-1">WHO classification of </a><a href="/articles/who-classification-of-cns-tumours-1">CNS tumours</a> <sup>6</sup>.</p><h4>Epidemiology</h4><p>They occur at all ages range from early childhood to 6th decade but are most commonly seen in children, adolescents, and young adults with a mean age between 10-30 years <sup>2,5</sup>. A female predilection has been suggested in some reports <sup>5</sup>. </p><h4>Pathology</h4><p>Astroblastomas have not yet been given a WHO grade, but do have a range of histological appearance and biological behaviour ranging from relatively indolent (astroblastoma) to aggressive (anaplastic or malignant astroblastoma) <sup>4,5</sup>. </p><h5>Macroscopic appearance</h5><p>They are well-demarcated masses with areas of cystic degeneration and necrosis giving it a bubbly appearance. Haemorrhage and adjacent brain infiltration are rare.</p><h5>Microscopic appearance</h5><p>Astroblastomas have elongated glial cells with abundant eosinophilic cytoplasm and a broad, or “stout”, <a href="/articles/glial-fibrillary-acid-protein-gfap">GFAP</a> positive process extending radially towards a central blood vessel, forming "astroblastic pseudorosettes", reminiscent to the <a href="/articles/perivascular-pseudorosettes-ependymoma">perivascular pseudorosettes</a> of <a href="/articles/ependymoma">ependymomas</a>, which are a characteristic feature of this tumour. The central vessel tends to be hyalinized. </p><p>Although no agreed-upon criteria have been accepted, anaplastic/malignant histological features include <sup>5</sup>: </p><ul>
  • +<p><strong>Astroblastomas</strong> are rare glial tumours usually found in the cerebral hemispheres of young adults and children. </p><h4>Terminology</h4><p>The exact nature of astroblastomas remains to be fully elucidated. Tumours with compatible histological features have a variety of molecular characteristics and overlap with other better-known tumours such as <a href="/articles/pleomorphic-xanthoastrocytoma">pleomorphic xanthoastrocytomas</a> or <a href="/articles/ependymoma">ependymomas</a> or <a href="/articles/astrocytic-tumours">diffuse astrocytomas</a> <sup>6,7</sup>. </p><p>The presence of MN1 alterations (a transcriptional coregulator involved in the development of acute myeloid leukaemia and meningiomas) is now used to define the lesion,  and thus it is now named <strong>astroblastoma, MN1-altered</strong> and considered <a href="/articles/astrocytic-tumours">circumscribed astrocytic gliomas</a> in the current (5th Edition, 2021) <a href="/articles/who-classification-of-cns-tumours-1">WHO classification of </a><a href="/articles/who-classification-of-cns-tumours-1">CNS tumours</a> <sup>6</sup>.</p><h4>Epidemiology</h4><p>They occur at all ages, ranging from early childhood to the 6th decade but are most commonly seen in children, adolescents, and young adults with a mean age between 10-30 years <sup>2,5</sup>. A strong female predilection has been suggested in some reports <sup>5,6</sup>. </p><h4>Pathology</h4><p>Astroblastomas have not yet been given a WHO grade, but do have a range of histological appearance and biological behaviour ranging from relatively indolent (astroblastoma) to aggressive (anaplastic or malignant astroblastoma) <sup>4,5</sup>. </p><h5>Macroscopic appearance</h5><p>They are well-demarcated masses with areas of cystic degeneration and necrosis giving it a bubbly appearance. Haemorrhages and adjacent brain infiltration are rare.</p><h5>Microscopic appearance</h5><p>Astroblastomas have elongated glial cells with abundant eosinophilic cytoplasm and a broad, or “stout”, <a href="/articles/glial-fibrillary-acid-protein-gfap">GFAP</a> positive process extending radially towards a central blood vessel, forming "astroblastic pseudorosettes", reminiscent to the <a href="/articles/perivascular-pseudorosettes-ependymoma">perivascular pseudorosettes</a> of <a href="/articles/ependymoma">ependymomas</a>, which are a characteristic feature of this tumour. The central vessel tends to be hyalinized. </p><p>Although no agreed-upon criteria have been accepted, anaplastic/malignant histological features include <sup>5</sup>: </p><ul>
  • -</ul><h4>Radiographic features</h4><p>Astroblastomas are usually fairly sizable, peripherally located, supratentorial lobulated solid cystic masses with little if any associated vasogenic oedema <sup>1-5</sup>. Multiple cysts are common and can give it a bubbly appearance. Calcification is very common and seen in 85% of cases, and usually in a punctate pattern.</p><h5>MRI</h5><p>Reported signal characteristics include</p><ul>
  • +</ul><h4>Radiographic features</h4><p>Astroblastomas are usually fairly sizeable, peripherally located, supratentorial lobulated solid cystic masses with little if any associated vasogenic oedema <sup>1-5</sup>. Multiple cysts are common and can give it a bubbly appearance. Calcification is very common and seen in 85% of cases, and usually in a punctate pattern.</p><h5>MRI</h5><p>Reported signal characteristics include <sup>2</sup>:</p><ul>
  • -<strong>T2/FLAIR:</strong> heterogeneously hyperintense</li>
  • +<strong>T2/FLAIR</strong><ul>
  • +<li>
  • +<strong>​</strong>heterogeneous with a multicystic or bubbly appearance</li>
  • +<li>solid components tend to be isointense to grey matter</li>
  • +<li>relatively little surrounding oedema compared to size</li>
  • +</ul>
  • +</li>
  • +<li>
  • +<strong>DWI/ADC</strong><ul>
  • +<li>​facilitated diffusion in fluid/cystic components</li>
  • +<li>intermediate ADC values of the solid component (1190 to 1250 x 10<sup>-6  </sup>mm<sup>2</sup>/s) <sup>8</sup>
  • +</li>
  • +</ul>
  • +</li>
  • -<a href="/articles/astrocytic-tumours">astrocytoma</a>, particularly <a href="/articles/glioblastoma-idh-wildtype">GBM</a> or <a href="/articles/gemistocytic-astrocytoma">gemistocytic</a>
  • +<a href="/articles/astrocytic-tumours">astrocytoma</a>, particularly <a href="/articles/glioblastoma-idh-wildtype">GBM</a> or <a href="/articles/gemistocytic-astrocytoma-historical">gemistocytic</a>

References changed:

  • 8. Sener R. Astroblastoma: Diffusion MRI, and Proton MR Spectroscopy. Comput Med Imaging Graph. 2002;26(3):187-91. <a href="https://doi.org/10.1016/s0895-6111(01)00042-8">doi:10.1016/s0895-6111(01)00042-8</a>

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