Hemangioblastoma

KEY FACTS

TERMINOLOGY

• Hemangioblastoma (HGBL): Highly vascular tumor of adults

most commonly found in posterior fossa (PF), spinal cord

○ 25-40% of HGBLs in von Hippel-Lindau disease (VHL)

IMAGING

• Best diagnostic clue: Adult with cerebellar mass with cyst

and enhancing mural nodule

• General features

○ 50-60% cyst + "mural" nodule; 40% solid enhancing mass

○ 90-95% in posterior fossa

○ 5-10% supratentorial (around optic pathways,

hemispheres; usually in VHL)

TOP DIFFERENTIAL DIAGNOSES

• Metastasis (most common posterior fossa parenchymal

mass in adults)

• Pilocytic astrocytoma (most common neoplasm with cyst +

nodule in child)

• Cavernous malformation

• Hereditary hemorrhagic telangiectasia

PATHOLOGY

• WHO grade I

• Red or yellowish, well-circumscribed, unencapsulated,

highly vascular mass that abuts leptomeninges

• Histology shows stromal cells, innumerable small vessels

CLINICAL ISSUES

• Headache is most common presenting symptom

• Primary therapy = surgical resection

• Begin MR screening of patients from VHL families after 10

years of age

DIAGNOSTIC CHECKLIST

• Most common posterior fossa intraaxial mass in middleaged/older adult is metastasis, not HGBL

(Left) Coronal graphic shows a

classic cerebellar

hemangioblastoma as largely

cystic mass ﬈ with a vascular

tumor nodule ﬇ that abuts

the pial surface. These lowgrade tumors are the most

common primary posterior

fossa tumor in adults. (Right)

Coronal T1 C+ MR shows a

large cyst and mural nodule

ſt in a VHL patient with

multiple hemangioblastomas.

Note the lack of enhancement

﬈ of the cyst wall, which

consists of compressed but

normal cerebellum. The other

hemangioblastomas ﬇ have a

solid enhancing appearance.

(Left) Coronal T2 MR in a 60-

year-old woman with

headaches shows a

heterogeneous cerebellar

mass ſt with prominent flow

voids ﬊ and surrounding

edema. (Right) Coronal T1 C+

MR in the same patient shows

marked enhancement of the

mass ﬇ and a prominent

adjacent vessel ſt.

Hemangioblastoma was found

at surgical resection. The main

imaging differential diagnosis

in this adult was metastatic

disease. These WHO grade I

tumors have an excellent

prognosis in sporadic cases.

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Primary CNS Lymphoma

KEY FACTS

TERMINOLOGY

• Malignant primary CNS neoplasm primarily composed of B

lymphocytes (PCNSL)

IMAGING

• Best diagnostic clue: Enhancing lesion(s) within basal

ganglia &/or periventricular white matter

• 60-80% supratentorial

○ Often involve, cross corpus callosum

○ Frequently contact, extend along ependymal surfaces

• Classically hyperdense on CT (helpful for diagnosis)

• Diffusely enhancing periventricular mass in

immunocompetent patients

• May see hemorrhage or necrosis in immunocompromised

patients

• DWI: Low ADC values

• PWI: Low relative cerebral blood volume ratios

• Periventricular location and subependymal involvement is

characteristic of PCNSL

• Corpus callosum involvement may be seen with PCNSL,

glioblastoma (GBM), and rarely metastases or

demyelination

TOP DIFFERENTIAL DIAGNOSES

• Acquired toxoplasmosis

• GBM

• Abscess

• Progressive multifocal leukoencephalopathy

PATHOLOGY

• 98% diffuse large B-cell, non-Hodgkin lymphoma

CLINICAL ISSUES

• Imaging and prognosis vary with immune status

• 6.6% of primary brain tumors, incidence rising

• Poor prognosis

• Stereotactic biopsy, followed by chemotherapy, ± XRT

(Left) Axial graphic shows

multiple periventricular

lesions with involvement of

the basal ganglia, thalamus,

and corpus callosum, typical of

primary CNS lymphoma

(PCNSL). Note the extensive

subependymal spread of the

disease ﬈. PCNSL typically

extends along ependymal

surfaces. (Right) Axial T1 C+

MR in a 63 year old shows the

classic appearance of PCNSL.

Note the multiple

homogeneously enhancing

masses in the basal ganglia

along the ependymal lining of

the ventricular system ﬈.

(Left) Axial T1 C+ MR shows a

homogeneously enhancing

mass crossing the corpus

callosum splenium ﬊ typical

of PCNSL in this 76-year-old

man with a headache. The

main differential

consideration would be a

glioblastoma, which typically

has a more heterogeneous

appearance. (Right) Axial

T1WI C+ MR in an AIDS patient

shows a ring-enhancing mass

with a target sign ﬈,

suggestive of toxoplasmosis.

Hemorrhage, necrosis, and

ring-enhancing lesions are

typical of PCNSL in AIDS

patients.

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Germinoma

KEY FACTS

TERMINOLOGY

• Intracranial germ cell tumor (iGCT)

• iGCTs are intracranial homologue of gonadal germinomas

(ovarian dysgerminoma, testicular seminoma)

IMAGING

• Most common: In/near midline (80-90%)

○ Pineal region ~ 50-65%

○ Suprasellar ~ 25-35%

• Less common: Basal ganglia/thalami ~ 5-10%

• 20% multiple

○ Most common = pineal with suprasellar

• Pineal germinoma

○ Hyperdense pineal region mass engulfs pineal Ca++

○ Strong, often heterogeneous enhancement

○ T2/FLAIR hyperintensity in surrounding brain =

inflammation/granulomatous change

• Suprasellar germinoma

○ Absent posterior pituitary "bright spot"

○ "Fat" stalk/pituitary gland

○ Strong, relatively uniform enhancement

○ May have cysts, hemorrhage (rare)

• Basal ganglia germinoma

○ Rare; hemorrhage common

TOP DIFFERENTIAL DIAGNOSES

• Pineal germinoma

○ Pineocytoma, other pineal GCTs

• Suprasellar germinoma ("fat" infundibulum)

○ Adult = neurosarcoid, metastases

○ Child = Langerhans cell histiocytosis (LCH)

CLINICAL ISSUES

• 90% of patients < 20 years old

○ Pineal region germinoma: M:F ~ 10:1

○ Causes dorsal midbrain syndrome

DIAGNOSTIC CHECKLIST

• Child with diabetes insipidus? Think germinoma or LCH!

(Left) Sagittal graphic shows

synchronous germinomas in

the suprasellar and pineal

regions. Note the

cerebrospinal fluid spread of

tumor in the lateral, 3rd, and

4th ventricles ﬈. (Right) Axial

NECT scan shows typical

findings of pineal germinoma

with a well-demarcated

slightly hyperdense mass ſt

engulfing the calcified pineal

gland ﬇.

(Left) Axial T2WI in a 14-yearold boy with visual symptoms

shows a suprasellar mass ﬈

that is slightly hypointense

relative to gray matter. A 2nd,

smaller mass ﬉ is present in

the pineal gland. (Right) T1 C+

MR in the same patient shows

that the lobulated suprasellar

mass ﬈ enhances strongly.

The pineal mass ﬉ also

enhances uniformly. The

combination of suprasellar

and pineal mass (sometimes

called "double midline"

germinoma) occurs in ~ 20%

of cases.

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Medulloblastoma

KEY FACTS

TERMINOLOGY

• Medulloblastoma (MB)

○ Malignant, invasive, highly cellular embryonal tumor

• 4 distinct MB molecular subgroups

○ Wingless (WNT)

○ Sonic hedgehog (SHH)

○ Group 3

○ Group 4

IMAGING

• MB subgroups arise in different locations

○ Midline (4th ventricle)

– Predominately (but not exclusively) groups 3 and 4

○ Cerebellar peduncle/CPA cistern: WNT

○ Cerebellar hemispheres (lateral): SHH

• NECT: 90% hyperdense (Ca++, hemorrhage uncommon)

• MR: > 90% enhance (group 4 minimal/no enhancement)

○ Restricted diffusion, low ADC

○ T1 C+ essential to detect CSF dissemination

TOP DIFFERENTIAL DIAGNOSES

• Atypical teratoid/rhabdoid tumor

• Ependymoma

• Cerebellar pilocytic astrocytoma

PATHOLOGY

• WHO grade IV (overstates risk of WNT MB)

• Microscopy

○ "Small round blue cell" tumor

○ Neuroblastic (Homer Wright) rosettes (40%)

• Most common histologic type = classic MB

• Less common subtypes: Desmoplastic, MB with extensive

nodularity, large cell/anaplastic

CLINICAL ISSUES

• Most common malignant pediatric brain tumor

• Prognosis varies with subgroup, mutations

○ WNT best, group 3 worst

(Left) Axial graphic shows a

spherical tumor centered in

the 4th ventricle ﬊, typical of

classic medulloblastoma (MB).

Cerebrospinal fluid (CSF)

dissemination ("sugar icing") is

common at initial diagnosis

and is shown in blue ﬈.

(Right) Axial T1WI shows

imaging findings of classic MB,

with a rounded, slightly

hypointense mass ﬈ in the

4th ventricle.

(Left) Axial T1 C+ FS in the

same case shows the mass

mass ﬇ enhances strongly,

somewhat heterogeneously.

No CSF spread is identified.

(Right) DWI in the same case

shows strongly restricted

diffusivity ﬇. Surgery

disclosed MB, desmoplastic

subtype. The midline 4th

ventricle is the 2nd most

common location for

desmoplastic MBs and the

most common site for classic

MBs. Histopathology disclosed

desmoplastic MB, Sonic

hedgehog subtype.

Cysts, and Disorders

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Pineocytoma

KEY FACTS

TERMINOLOGY

• Pineocytoma (PC), pineal parenchymal tumor (PPT)

• PCs are composed of small, uniform, mature cells

○ Cells resemble pineocytes

IMAGING

• General features: Circumscribed, enhancing pineal mass

○ May mimic benign pineal cyst or PPT of intermediate

differentiation (PPTID)

○ Typically < 3 cm

○ May compress adjacent structures

○ Rarely extends into 3rd ventricle, rarely invasive

○ Can compress aqueduct → hydrocephalus

• CT

○ Circumscribed iso-/hypodense pineal region mass

○ Peripheral ("exploded") Ca++ common

○ CECT: Enhances (solid, ring, nodular)

• MR (most sensitive)

○ Cystic change may be present

○ Enhancement may be solid or peripheral

TOP DIFFERENTIAL DIAGNOSES

• Nonneoplastic pineal cyst

• PPTID

• Pineoblastoma

• Germinoma, other germ cell tumors

CLINICAL ISSUES

• Headache, dorsal midbrain (Parinaud) syndrome most

common features

• Increased intracranial pressure, ataxia, hydrocephalus,

mental status changes may occur

• Most common in adults, mean 40 years

• Stable or slow-growing tumor

• Germ cell markers (α-fetoprotein, hCG) absent

• Surgical excision or stereotactic biopsy is primary treatment

○ Complete surgical resection generally curative

(Left) Sagittal graphic shows a

cystic pineal gland mass ﬈

with a fluid-fluid level and

nodular tumor along the

periphery of the mass, typical

of pineocytoma. No significant

mass effect is present.

Pituicytomas may be found

incidentally or present with

hydrocephalus. (Right) Axial

NECT shows a classic example

of a pineocytoma. Note the

"exploded" peripheral

calcification ſt in this small

mass that arises from the

pineal region. The tumor is just

over 1 cm in size. There is no

hydrocephalus.

(Left) Sagittal T1 MR of a 50-

year-old woman with

headache shows a cystic

pineal region mass ſt with

associated ventriculomegaly

st and local mass effect on

the tectum ﬊. Mass effect on

the superior tectum often

results in dorsal midbrain

(Parinaud) syndrome. (Right)

Axial FLAIR MR in the same

patient shows the

hyperintense, lobular pineal

region mass ſt with

associated ventriculomegaly.

Pineocytoma was diagnosed

at resection. These WHO

grade I tumors are often

stable for years.

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Pineal Parenchymal Tumor of Intermediate Differentiation (PPTID)

KEY FACTS

TERMINOLOGY

• Primary parenchymal neoplasm of pineal gland

○ Intermediate in malignancy between pineoblastoma and

pineocytoma

IMAGING

• General features

○ Aggressive-looking pineal mass in adult

○ Extension into adjacent structures (ventricles, thalami) is

common

○ Lobulated, moderately vascular

○ Size varies from small (< 1 cm) to large (~ 6 cm)

• CT

○ Hyperdense mass centered in pineal region

○ Engulfs pineal gland Ca++

○ Hydrocephalus

• MR

○ T1: Mixed iso-/hypointense mass

○ T2: Isointense with gray matter, + small hyperintense foci

○ FLAIR: Hyperintense

○ Strong, heterogeneous enhancement

○ MRS: Elevated Cho, decreased NAA

• If aggressive-looking pineal region tumor in middle-aged,

older adult, consider PPTID

TOP DIFFERENTIAL DIAGNOSES

• Germinoma

• Pineocytoma

• Pineoblastoma

• Papillary tumor of pineal region

PATHOLOGY

• Neuroepithelial neoplasm

○ Arises from pineocytes or their precursors

• WHO grade II or III

CLINICAL ISSUES

• Dorsal midbrain (Parinaud) syndrome, headache

○ Upgaze paralysis, convergence-retraction nystagmus

(Left) Sagittal T1WI MR in a

21-year-old man with

headache shows a pineal

region mass ﬈ with

obstructive hydrocephalus,

enlargement of the 3rd

ventricle ﬇, and cerebellar

tonsillar descent ſt. Imaging

differential considerations

include PPTID, pineoblastoma,

and germinoma. (Right) Axial

T2WI MR shows a very large

PPTID ﬈ with extension into

the ventricular system. Note

the heterogeneous T2

appearance of the mass with

multiple cystic regions ﬇,

typical of PPTID. (Courtesy L.

Loevner, MD.)

(Left) Coronal T1WI C+ MR

shows a large, peripherally

enhancing pineal mass ſt in a

24-year-old man. PPTID was

diagnosed at resection. (Right)

MRs in a 48-year-old woman

shows elevated choline,

decreased NAA, and a lactate

doublet. Imaging is too

aggressive for a pineocytoma.

Germinomas are rare in

middle-aged women. Imaging

is most suggestive of a PPTID,

although a papillary tumor of

the pineal region would be a

possible diagnosis. PPTID was

confirmed at histologic

examination.

Cysts, and Disorders

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Central Neurocytoma

KEY FACTS

TERMINOLOGY

• Central neurocytoma (CN) = intraventricular neuroepithelial

tumor with neuronal differentiation

IMAGING

• Best diagnostic clue: "Bubbly" mass in frontal horn or body

of lateral ventricle

○ May involve 3rd ventricle

• CT: Usually mixed solid and cystic mass with calcification

○ Hydrocephalus common

○ Rarely complicated by hemorrhage

• MR: Heterogeneous, T2 hyperintense, "bubbly" appearance

○ May be predominantly solid mass

○ Moderate to strong heterogeneous enhancement

• MRS: ↑ Cho, ↓ N-acetylaspartate; glycine peak at 3.55 ppm

• If "bubbly," "feathery," or solid intraventricular mass near

foramen of Monro in young adult, consider CN

TOP DIFFERENTIAL DIAGNOSES

• Subependymoma

• Subependymal giant cell astrocytoma

• Intraventricular metastasis

• Ependymoma

• Choroid plexus papilloma

CLINICAL ISSUES

• Young adults, commonly 20-40 years of age

• Usually benign, local recurrence is uncommon

○ Surgical resection is typically curative

○ If incomplete resection, radiation therapy,

chemotherapy, &/or radiosurgery may be helpful

• 5-year survival rate: 90%

• MIB-1 (Ki-67 labeling) index > 2-3% = poorer prognosis

• Headache, increased intracranial pressure, mental status

changes, seizure are most common presenting features

○ Hydrocephalus secondary to foramen of Monro

obstruction

(Left) Axial graphic shows a

circumscribed, lobular,

"bubbly" mass ﬇ attached to

the septum pellucidum ﬈.

Ventricular dilatation is

related to foramen of Monro

obstruction. This is the classic

appearance of a central

neurocytoma. Complete

surgical resection is often

curative for these WHO grade

II tumors. (Right) Axial NECT

shows a heterogeneous mixed

cystic/solid mass ﬈ in the

lateral ventricles attached to

the septum pellucidum. There

is associated obstructive

hydrocephalus ﬇, typical for

central neurocytoma.

(Left) Axial T2WI MR in a 20

year old with headaches

shows a predominantly solid

ventricular mass in the body of

the lateral ventricle ﬈

attached to the septum

pellucidum with prominent

flow voids ﬊. (Right) Axial

T1WI C+ MR in the same

patient shows diffuse

enhancement ﬈. Central

neurocytoma was diagnosed

at resection. Imaging

differential considerations

include subependymal giant

cell astrocytoma,

subependymoma, and

meningioma. (Courtesy S. van

der Westhuizen, MD.)

Cysts, and Disorders

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Ganglioglioma

KEY FACTS

TERMINOLOGY

• Well-differentiated, slowly growing neuroepithelial tumor

composed of neoplastic ganglion cells and neoplastic glial

cells

• Most common neoplastic cause of temporal lobe epilepsy

(TLE)

IMAGING

• Best diagnostic clue: Partially cystic, enhancing, cortically

based mass in child/young adult with TLE

• Can occur anywhere, but most commonly superficial

hemispheres, temporal lobe (> 75%)

• Circumscribed cyst with mural nodule most common

• May be solid and appear well circumscribed

• Calcification is common (up to 50%)

• Superficial lesions may expand cortex, remodel bone

• ~ 50% enhance

• Protocol advice: Contrast-enhanced MR to include coronal

T2 images for better evaluation of temporal lobes

TOP DIFFERENTIAL DIAGNOSES

• Pleomorphic xanthoastrocytoma

• Dysembryoplastic neuroepithelial tumor

• Astrocytoma

• Oligodendroglioma

• Neurocysticercosis

PATHOLOGY

• WHO grade I or II (80% grade I)

• Uncommon: Anaplastic ganglioglioma (WHO III)

• Rare: Malignant with glioblastoma multiforme-like glial

component (WHO IV)

CLINICAL ISSUES

• Occurs at all ages (peak: 10-20 years)

• Most common mixed neuronal-glial tumor

• Cortical dysplasia is commonly associated with

ganglioglioma

• Excellent prognosis if surgical resection complete

(Left) Coronal graphic shows a

discrete cystic and solid

temporal lobe mass expanding

the overlying cortex. Calvarial

remodeling is seen, typical of a

superficially located

ganglioglioma.

Gangliogliomas are the most

common tumors to cause

temporal lobe epilepsy. (Right)

Coronal T1WI C+ MR in a

young adult with temporal

lobe epilepsy shows a

circumscribed, cystic, and solid

temporal lobe mass with

intense enhancement of the

mural nodule ſt. This is the

classic enhancement pattern

of a ganglioglioma.

(Left) Axial CT shows a

partially calcified frontal lobe

mass ﬈ in a 25-year-old

patient with headaches and

seizures. The lack of

surrounding edema is typical

for ganglioglioma. Imaging

mimics an oligodendroglioma.

Calcification is seen in 30-50%

of gangliogliomas. (Right)

Coronal T1WI C+ MR shows

subtle enhancement ﬇ within

a right temporal lobe

ganglioglioma in a female

patient with seizures. The

differential diagnosis for this

lesion includes DNET,

astrocytoma, PXA, and

oligodendroglioma.

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Dysembryoplastic Neuroepithelial Tumor (DNET)

KEY FACTS

TERMINOLOGY

• Dysembryoplastic neuroepithelial tumor (DNET)

○ Benign mixed glial-neuronal neoplasm

○ Frequently associated with cortical dysplasia

IMAGING

• May occur in any region of supratentorial cortex

○ Temporal lobe most common, followed by frontal lobe

○ Mass frequently "points" toward ventricle

• Sharply demarcated, wedge-shaped

○ Cystic ("bubbly") intracortical mass

○ Minimal/no mass effect

○ No surrounding edema

• Slow growth over years

• Usually does not enhance

• Faint focal punctate or ring enhancement in 20-30%

○ Higher rate of recurrence if enhancement

TOP DIFFERENTIAL DIAGNOSES

• Focal cortical dysplasia type II (Taylor type)

• Neuroepithelial cyst

• Ganglioglioma

• Pleomorphic xanthoastrocytoma

• Angiocentric glioma

PATHOLOGY

• WHO grade I

• Hallmark = specific glioneuronal element

CLINICAL ISSUES

• Longstanding drug-resistant partial complex seizures in

child/young adult

• Surgical resection usually curative

• Histology usually remains benign even if tumor recurs,

enhances

(Left) Coronal oblique graphic

shows typical appearance of a

cystic cortical

dysembryoplastic

neuroepithelial tumor (DNET),

which present in children or

young adults with seizures.

The gyrus is expanded by the

multicystic tumor ﬈; cortical

dysplasia ﬊ is common in

adjacent brain. (Right) Sagittal

T1 MR in a young adult with

seizures shows characteristic

"bubbly" appearance of DNET

(WHO grade I neoplasm). Note

low T1 signal within the

wedge-shaped cortical mass

﬇; there's excellent prognosis

with surgical resection.

(Left) Axial T2WI MR shows a

multilobular, wedge-shaped

cystic cortically based mass ﬈

in the right posterior frontal

lobe. Note the lack of edema

and mass effect, given the size

of the tumor, which is typical

of a DNET. (Right) Axial FLAIR

MR in the same patient shows

the characteristic appearance

of a DNET. Note the cortically

based, sharply demarcated,

wedge-shaped mass with a

hyperintense rim ſt. The

tumor points toward the

ventricle, and there is no

surrounding edema. (Courtesy

L. Loevner, MD.)

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