Diffuse astrocytoma, MYB- or MYBL-altered

Diffuse astrocytoma, MYB- or MYBL-altered
Diagnosis in short
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 pediatric astrocytoma. It is very rare.

Microscopic

Features:

• Classically biphasic (though either may be absent):
  1. Fibrillar.
  2. Microcystic/loose.
• Hair-like fibres ~ 1 micrometer; pilo- = hair.
  • Best seen on smear or with GFAP IHC.
• Rosenthal fibres - key feature.
  • May be rare. Not pathognomonic (see below).
• Eosinophilic granular bodies.
• Low cellularity - when compared to medulloblastoma and ependymoma.

Notes:

• +/-Microvascular proliferation.
• +/-Focal necrosis.
  • Necrosis with pseudopalisading more likely glioblastoma.
• +/-Mitoses - not significant in the context of the Dx.

DDx

• Normal white matter
• Angiocentric glioma

IHC

Features:

• GFAP +ve (fibres).

Prognosis

• Excellent (

See also

• Neuropathology tumours.
• Astrocytoma.