Diffuse astrocytoma MYB or MYBL1 altered

Last revised by Frank Gaillard on 24 Jul 2023

Diffuse astrocytoma MYB or MYBL1 altered is a newly recognized IDH wildtype pediatric-type diffuse low-grade glioma included in the 5th Edition (2021) WHO brain tumor classification 1. It has a generally favorable prognosis and is often associated with seizures 4.

Diffuse astrocytoma MYB or MYBL1 altered occurs in children and young adults (median age 5 years; range 0-26 years) 3.

Diffuse astrocytoma MYB or MYBL1 altered is closely related, from a molecular point of view, to angiocentric gliomas that also share MYB alterations but lack their histological features 8.

They are also closely related to isomorphic diffuse gliomas, not yet recognized as a distinct entity under the current (2021) WHO brain tumor classification, that also share MYBL1 alterations but tend to occur in adults and have a distinct methylation profile 8.

  • hemispheres

  • diencephalon

  • brainstem 3

Non-specific and low-grade histopathologic features with rare or absent mitotic activity 1,3.

As these tumors are histologically non-specific it is essential to identify MYB/MYBL1 mutations for the diagnosis.

  • MYB or MYBL1 alternations 1,3,4

  • H3 wildtype

  • IDH wildtype

The hemispheric cortical tumors appear as lobulated and infiltrative masses, while poorly defined and diffuse in the diencephalon and brainstem 3.

  • T1: iso- or hypointense

  • T2/FLAIR: heterogeneous hyperintensity

  • DWI/ADC: no restricted diffusion

  • T1 C+ (Gd): no enhancement 3

Although further studies are needed, the prognosis of these tumors is generally good 3.

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