Anaplastic Astrocytoma

KEY FACTS

TERMINOLOGY

• Diffusely infiltrating malignant astrocytoma with anaplasia,

marked proliferative potential

IMAGING

• Infiltrating mass that predominately involves white matter

with variable enhancement

• T2 heterogeneously hyperintense

• Neoplastic cells almost always found beyond areas of

abnormal signal intensity

• May involve and expand overlying cortex

• Usually no enhancement; focal, nodular, homogeneous,

patchy enhancement less common

○ Ring enhancement is suspicious for glioblastoma (GBM)

• MRS: Increased Cho/Cr ratio, decreased N-acetylaspartate

• MRP: Elevated maximum regional cerebral blood volume

• Anaplastic astrocytomas have histologic and imaging

characteristics along spectrum between low-grade

astrocytoma and GBM

TOP DIFFERENTIAL DIAGNOSES

• Low-grade diffuse astrocytoma

• GBM

• Oligodendroglioma

• Cerebritis

• Ischemia

PATHOLOGY

• WHO grade III

• Usually evolves from low-grade (diffuse) astrocytoma

(WHO grade II) (75%)

CLINICAL ISSUES

• Occurs at all ages, most common 40-50 years; 1/3 of

astrocytomas

• Prognosis: Median survival: 2-3 years

○ IDH1(+) and MGMT(+) associated with increased survival

○ IDH1, ATRX wild-type (not mutated) = poor prognosis

(Left) Axial graphic shows an

infiltrative white matter mass

with extension along the

corpus callosum, focal

hemorrhage ſt, and local

mass effect. White matter

extension is typical of

anaplastic astrocytoma (AA).

They are most commonly

located in the cerebral

hemispheres. (Right) Axial T2

MR shows a heterogeneously

hyperintense mass with local

mass effect ﬈ in the frontal

lobe. AA, WHO grade III, was

diagnosed at resection. These

high-grade gliomas have a

tendency to degenerate into

glioblastomas (GBM).

(Left) MRS image in a patient

with a tectal anaplastic

astrocytoma shows a typical

malignant tumor spectrum

with a high choline peak ſt

and a low N-acetylaspartate

peak ﬇. (Right) Coronal

FLAIR MR in a 47-year-old man

shows a heterogeneously

hyperintense mass ﬊

centered in the frontal lobe

white matter. Anaplastic

astrocytomas represent 1/3 of

all astrocytomas. Anaplastic

astrocytomas are intermediate

between low-grade (diffuse)

astrocytoma (WHO grade II)

and GBM (WHO grade IV).

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

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