Diffuse astrocytoma, MYB- or MYBL-altered

Diffuse astrocytoma, MYB- or MYBL-altered
Diagnosis in short
Diffuse astrocytoma, MYB- or MYBL-altered H&E stain.
LM DDx	Angiocentric glioma
IHC	GFAP +ve
Gross	soft, unencapsulated
Site	brain - usu. temporal
Prevalence	common - esp. in children
Prognosis	good (WHO Grade I)

Diffuse astrocytoma, MYB- or MYBL-altered is a low-grade, often pediatric-onset astrocytoma. It is very rare.

General

• CNS WHO grade 1.
• Entity introduced in 2021.
• Rare epilepsy-associated tumor.
• Median time to surgery often exceeds more than 10 years.
• No sex predilection.

Imaging

• T1 hypointense.
• Non-enhancing.
• Occasionally large cysts.

Gross

• Soft, unencapsulated.
• Grey to white.

Microscopic

Features:

• Diffusely growing.
• Minimal incereased cell density.
• Monomorphic, bland glial cells.
• Entrapped neurons.
• Usu. no mitotic activity

Notes:

• Focally angiocentric pattern may be present.

DDx

• Normal white matter
• Angiocentric glioma

Images

• 

  H&E

Stains

Features:

• GFAP +ve.
• Olig2 -ve.
• MAP2 -ve.
• CD34 -ve.
• ATRX retained.

Molecular

• Structural variant of MYB or MYBL1 (most common fusion partners: MAML2, MMP16 , PCDGHA1).
• IDH1/2 wildtype.
• H3F3A wildtype.

Prognosis

• Excellent (most cases are stable after surgery).

See also

• Neuropathology tumours.
• Astrocytoma.