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Glioblastoma

KEY FACTS

TERMINOLOGY

• Rapidly enlarging malignant astrocytic tumor characterized

by necrosis and neovascularity

• Most common of all primary intracranial neoplasms

IMAGING

• Best imaging clue: Thick, irregularly enhancing rind of

neoplastic tissue surrounding necrotic core

• Heterogeneous, hyperintense mass with adjacent tumor

infiltration/vasogenic edema

• Necrosis, cysts, hemorrhage, fluid/debris levels, flow voids

(neovascularity) may be seen

• Supratentorial white matter most common location

○ Cerebral hemispheres > brainstem > cerebellum

• Viable tumor extends far beyond signal changes

TOP DIFFERENTIAL DIAGNOSES

• Neoplasms: Anaplastic astrocytoma, lymphoma, metastasis

• Tumefactive demyelination, subacute ischemia

PATHOLOGY

• Histology: Necrosis, microvascular proliferation, WHO IV

• Genetically heterogeneous

○ 4 major subtypes = classic, mesenchymal, proneural,

neural

○ Can be primary or secondary

– Primary (de novo) glioblastoma (GBM)

□ 95% of GBMs; most are classical; EGFR amplified,

IDH1(-) (wild-type)

– Secondary (arises from lower grade astrocytoma)

□ Younger patient; often proneural; IDH1, TP53 often

mutated

CLINICAL ISSUES

• Seizures, focal neurologic deficits common

• Peak: 45-75 years, but may occur at any age

• 12-15% intracranial neoplasms, 2/3 of astrocytomas

• Relentless progression, survival often < 1 year

○ Varies with genetic, other factors (e.g., MGMT status)

(Left) Axial graphic shows a

centrally necrotic infiltrating

mass with extension across

the corpus callosum; a

peripheral rind of tumor ﬈ is

seen surrounding the necrotic

core, typical of glioblastoma

(GBM). (Right) Axial T1WI C+

FS MR in a 60-year-old man

with acute onset of seizures

shows a heterogeneously

enhancing occipital lobe mass

with central necrosis and

extension across the splenium

of the corpus callosum st,

characteristic of GBM. The

frontal and temporal lobes are

the most common locations

for GBM.

(Left) Axial FLAIR MR shows a

heterogeneously hyperintense

mass ﬇ crossing the corpus

callosum genu with signal

abnormality extending into

the frontal lobe subcortical

white matter ſt. Viable tumor

cells may extend beyond the

area of MR signal abnormality.

(Right) Axial T1 C+ FS MR in

the same patient shows a

thick enhancing rind of tumor

that surrounds the necrotic

tumor core, characteristic of

GBM. Other lesions including

lymphoma and demyelination

may also involve the corpus

callosum.

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

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