Imaging of Common Adult and Pediatric Primary Brain Tumors€¦ · Imaging of Common Adult and Pediatric Primary Brain Tumors ... The review will focus on the initial imaging diagnostic

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maging of Common Adultnd Pediatric Primary Brain Tumorsumberto Morales, MD, and Mary Gaskill-Shipley, MD

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he primary goals of brain tumor imaging are lesion de-tection, localization, delineation of extent, and charac-

erization. This information is used to formulate an appropri-te differential diagnosis that is extremely helpful for theeferring neuro-surgeons and the neuro-oncologists.1,2 In ad-ition, imaging studies play a vital role in therapy planning,uch as stereotactic location for surgery or radiotherapy, andssessing response to therapy.3

This article discusses the imaging characteristics of severalommon pediatric and adult primary central nervous systemCNS) tumors. The review will focus on the initial imagingiagnostic workup and will give a useful radiological ap-roach based on age, localization, imaging characteristics,nd relative frequency of brain tumors. Advanced magneticesonance (MR) techniques including spectroscopy and per-usion can provide additional information of brain tumors.hese techniques will be discussed separately in this supple-ent.

lassificationhe World Health Organization (WHO) classifies primaryrain tumors according to their cellular origin. The majorategories include neuroepithelial tumors, tumors of the me-inges, lymphoma and hematopoietic neoplasms, germ cellumors, tumors of the cranial and paraspinal nerves, tumorsf the sellar region, metastatic tumors, and cysts and tumor-ike lesions.4,5 Tumors of neuroepithelial origin comprise a sig-ificant number of primary brain tumors, including astrocyto-as, oligodendrogliomas, ependymomas, choroid plexus

umors, neuronal and mixed neuronal-glial tumors, pineal le-ions, and embryonal tumors.

Grading of brain tumors is according to the WHO classi-cation that assigns a grade of 1-4 from benign to malignant,aking into account the presence of nuclear changes, mitoticctivity, endothelial proliferation, and necrosis. The proto-ypic WHO grade 1 tumor is the pilocytic astrocytoma (PA)

ivision of Neuroradiology, University Hospital, Cincinnati, OH.ddress reprint requests to Humberto Morales, MD, Division of Neuroradi-

ology, University Hospital, 231 Albert Sabin Way, Cincinnati, OH
r45267. E-mail: [email protected]
2 0037-198X/10/$-see front matter © 2010 Elsevier Inc. All rights reserved.doi:10.1053/j.ro.2009.09.006

hat has a 90% 5-year survival after resection whereas glio-lastoma multiforme (GBM) represents one of the most com-on WHO grade 4 tumors with a 4% or less survival at 5

ears.6

Although the final diagnosis and grading of brain tumors isetermined by histologic analysis, imaging can be very help-ul in the initial assessment of neoplasms and can, in manyases, help direct surgical biopsy or treatment. Imaging fea-ures associated with increasing malignancy include massffect, vasogenic edema, enhancement, necrosis, and hemor-hage, particularly when astrocytic tumors are compared.7,8

erebral blood volume (CBV), which can be calculated fromR perfusion studies and choline/creatine (Cho/Cr) ratios

ased on MR spectroscopy, are relatively elevated in malig-ant tumors, secondary to increased vascularity and cell pro-

iferation, respectively.8,9 However it is important to note thatome low-grade tumors can demonstrate “aggressive fea-ures” on imaging. In children, PAs may have a malignantppearance on conventional imaging, increased metabolismn positron emission tomographic images, and increasedCBV and Cho/Cr ratios.10,11 In adults, oligodendrogliomasften have increased rCBV.12,13

iagnostic Approach tontracranial Tumors Basedn Frequency, Age, Location,nd Imaging Characteristics

he radiologist’s ultimate goal in the initial imaging evalu-tion of brain tumors should be to provide an appropriateifferential diagnosis that will guide future interventionnd treatment. Accurate diagnosis is based not only on theadiological appearance of the tumor but also on the pa-ient’s age and the location and relative incidence of theesion (Table 1).14 Each of these factors must be taken intoccount.

The yearly incidence of primary brain tumors is 16.5 caseser 100,000 population or approximately 30,000-35,000ew cases per year. In comparison, intracranial metastasesre much more common with as many as 170,000 cases
eported each year. The overall incidence of primary tumors
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Imaging of primary brain tumors 93

ncreases with age. The pediatric population (0-19 years) haslow incidence rate of approximately 4.5 cases per 100,000opulation/year while the highest occurrence rate is observed

n patients older than 50 years of age, accounting for over 30ases per 100,000 population/year.6

The location and histology of primary brain tumors varyith age. Although the most common location for primaryeoplasms in both adults and children is the cerebral hemi-pheres; brain tumors in children have a special predilectionor the posterior fossa. In comparison, primary tumors lo-

able 1 Diagnostic Approach of Primary Brain Tumors by Age

Pediatric Brain Tumors

xtraaxialRare in pediatric population: schwannoma and meningiom

ntraaxialSupratentorial

CorticalNeuronal and mixed neural-glial (DNET, gangliogliom

and pleomorphic xanthoastrocytoma.Corticomedullary

Low-grade astrocytoma and S-PNET.Deep white matter

Fibrillary/anaplastic astrocytoma, supratentorialependymoma, and glioblastoma.

InfratentorialCerebellar hemisphere

Pilocytic astrocytoma (PA) and ATRT.ntraventricular

Fourth ventricleMedulloblastoma/PNET-MB and ependymoma.

Lateral ventricleChoroid plexus papilloma, SEGA, meningioma, ependym

and choroid plexus carcinoma.

idlineSuprasellar-chiasmatic-optic

Craniopharyngioma, PA, germinoma, LCH, hypothalamihamartoma, lipoma, dermoid, and PMA.

Pineal regionGerminoma, teratoma, and pineoblastoma.

BrainstemTectal glioma, focal/diffuse pontine, and medullary and

midbrain astrocytomas.ultiple spacesEmbryonal tumors (PNET, ependymoblastoma, and

neuroblastoma), ATRT.

bbreviations: DNET, dysembryoplastic neuroepithelial tumor; S-PNrhabdoid tumor; SEGA, subependymal giant cell astrocytoma; LC

ated in the cerebellum are unusual in adults. Therefore, in o

he adult population, a solitary lesion in the posterior fossa isost commonly a metastasis.Differentiating between an intra- and extraaxial location of

mass will significantly alter potential diagnoses. Althoughxtraaxial primary tumors, such as meningiomas, are com-on in adults, they are very uncommon in the pediatricopulation. Intraventricular tumors have a very specific dif-erential diagnosis, which can vary depending on which ven-ricle is involved. If a tumor is intraaxial, determination of itspecific location such as cortex, corticomedullary junction,

ation, and Relative Frequency

Adult Brain Tumors

ExtraaxialConvexities

Meningioma, hemangioendothelioma, andhemangioperycitoma.

Cerebello-pontine angleSchwannoma, meningioma, and epidermoid.

IntraaxialSupratentorial

CorticalPleomorphic xanthoastrocytoma.

CorticomedullaryOligodendroglioma and fibrillary/anaplastic

astrocytomaDeep white matter

Glioblastoma and fibrillary/anaplasticastrocytoma

Corpus callosum/periventricular white matterGlioblastoma, lymphoma, and gliomatosis

cerebri.Infratentorial

Cerebellar hemisphereHemangioblastoma and astrocytoma.

IntraventricularFourth ventricle

Subependymoma, choroid plexus papilloma, andependymoma.

Lateral ventricleMeningioma, ependymoma, central neurocytoma,

and subependymoma.Third ventricle

Colloid cyst, astrocytoma, and chordoid glioma.Midline

Sellar/suprasellarPituitary adenoma, meningioma, and

craniopharyngioma.Pineal region

Pineal cyst, pineocytoma, andepidermoid/dermoid.

Multiple spacesMalignant meningioma, hemangiopericytoma, and

lymphoma.

ratentorial primitive neuroectodermal tumor; ATRT, atypical teratoidngerhan’s cell histiocytosis; PMA, pilomyxoid astrocytoma.

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Different tumor types occur at very different rates at vari-us ages (Fig. 1). The most common tumor of childhood ishe PA, followed by medulloblastoma. However, in adult-ood, the most common tumor is meningioma, followed bylioblastoma. Oligodendroglioma, which is common indults, is very rare in children. Neuronal and mixed neural-lial tumors are more common in children than in adultsTable 1). Therefore, correlating the location and character-stics of a tumor with the age of the patient is crucial inetermining an appropriate differential diagnosis.

umors Moreommon in Childhood

ilocytic Astrocytoma (WHO Grade 1)A is the most common primary brain tumor in children.verall, patients with PA’s have a good prognosis after resec-

ion with a 94% survival rate at 10 years. Common locationsor PA’s include the cerebellum, optic nerve/chiasm/hypotha-amic region, or brain stem. Involvement of the cerebralemispheres is less frequent.Pilocytic astrocytomas are typically well-defined lesions

hat classically present as a cystic mass with an enhancingural nodule, however solid lesions do occur. Significant

asogenic edema is rare. These are slow growing tumors thatften present due to localized mass effect. Lesions occurringn the cerebellum may significantly compress the fourth ven-ricle, making it difficult to identify the tumor’s parenchymal

Figure 1 Distribution of primary brain and central nervou2000-2004). (Color version of figure is available online

rigin. The main differential diagnosis is between the 2 most m

ommon pediatric fourth ventricular tumors, medulloblas-oma (MB), and ependymoma (Fig. 2).15,16

PA’s occurring in the optic nerve/chiasm/hypothalamic re-ion have been separated into 3 subsets. In the pediatricopulation, tumors are divided into 2 types: those associatedith neurofibromatosis type 1 (NF1) and those not associ-

ted with NF1. PA’s in patients with NF1 are usually bilateralonenhancing tumors involving the optic nerves and lessommonly, the optic chiasm/hypothalamic region. Theyave an indolent course. PA’s in non-NF1 patients usually

nvolve the chiasm/hypothalamic region. They are typicallyolid/cystic enhancing tumors, which are often larger thanA’s associated with NF1 and have a less indolent course. Thehird subset of tumors, which is identified in adults, demon-trates more aggressive behavior.

As mentioned earlier, PA may demonstrate a false “aggres-ive appearance” on MR spectroscopy with significant eleva-ion of Cho/Cr ratios. Recent studies have shown very lowoncentrations of Cr in PA’s compared with other pediatricumors, as well as diminished quantities of total Cho. There-ore, the paradoxical increase in Cho/Cr ratios does not nec-ssarily indicate increased cell proliferation.17

edulloblastoma/NET-MB) (WHO Grade 4)B or PNET-MB (primitive neuroectodermal tumor-medul-

oblastoma) is a highly cellular, rapidly growing malignantmbryonal tumor. It is the second most common tumor inhildren but the most common posterior fossa lesion. These

m tumors by histology and age (Modified from CBTRUS
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rom the superior medullary velum. Involvement of the cer-bellar hemispheres is rare, usually occurring in older chil-ren and adults and typically representing desmoplastic me-ulloblastomas.18 MBs have a variable prognosis after resectionith a 50% survival rate at 10 years.MBs are typically isointense on T1 weighted images,ildly hypointense to cortex on T2 weighted images, andomogeneously enhance. The desmoplastic variant that has aetter prognosis often demonstrates a different imaging pat-ern characterized by calcifications and subtotal heteroge-eous enhancement.19 Diffusion restriction is commonly ob-

Figure 2 (A, D) Pilocytic astrocytoma in a 7-year-old girblastoma in a 3-year-old boy with headaches and vomi(A, B, C) Axial computed tomography (CT) noncontrastmid cerebellum slightly right to midline. Note the mass esolid mass centered in the fourth ventricle with small cnoted in the suprasellar region. (C) Isodense solid massAxial and sagittal T1 with gadolinium images. (D) Comportions causing significant effacement of the fourth veassociated with small enhancing lesion in the suprasellar(F) Lobulated heterogeneous enhancing mass extendingenlargement in all 3 patients secondary to obstructivCincinnati Children’s Hospital).

erved due to the tumor’s dense cellularity.20 Ninety percent p

f these lesions are dense on computed tomography (CT),hich can aid in the radiographic diagnosis (Fig. 2). Approx-

mately one-third of MB’s will have subarachnoid dissemina-ion at the time of presentation; therefore, imaging the entireeuroaxis is extremely important to evaluate the extent ofisease.Supratentorial primitive neuroectodermal tumors (S-PNET)

re a subset of tumors genetically distinct from infratento-ial PNETs (PNET-MB). Though only 6% of PNETs areupratentorial, they are important hemispheric masses toonsider in newborns and infants. S-PNETs are large, com-

eadaches, vomiting, and papilledema. (B, E) Medullo-, F) Ependymoma in a 2-year-old girl with vomiting.

. (A) Isodense complex cystic-solid mass centered in theon the fourth ventricle. (B) Hyperdense predominantly

ecrotic areas. An additional small hyperdense lesion isfourth ventricle with speckled calcifications. (D, E, F)

ass with peripheral enhancement of the cystic/necrotic. (E) Solid enhancing mass within the fourth ventricle,most consistent with cerebrospinal fluid dissemination.rough the floor of the fourth ventricle. Note ventricularocephalus (Images courtesy of Dr. Blaise Jones, MD,

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nd minimal peritumoral edema.21 The differential diagnosisf these lesions includes teratoid or rhabdoid tumors andpendymomas. Unlike PNET-MB, calcifications, hemor-hage, and necrosis are common (Fig. 3). Patients with-PNET have decreased survival compared to those withNET-MB.

pendymoma (WHO Grade 2)pendymomas are the fourth most common posterior fossa

Figure 3 Supratentorial primitive neuroectodermal tumolarge mass centered in the trigone of the left lateral ventriThere are multiple calcifications and enlargement of thethe right frontal horn. (B) Axial T2 image shows a large mpredominantly in the periphery and cortical region(C) Coronal T1 with gadolinium image shows heterogenthe ventricle and brain parenchyma as well as extendinspaces is an important characteristic of supratentorial prJones, MD, Cincinnati Children’s Hospital).

umor in the pediatric population.22 They arise from ependy- n

al cells lining the ventricles and are most commonly located inhe fourth ventricle. Unlike medulloblastomas, which originateuperiorly from the medullary velum, ependymomas arise fromhe floor of the fourth ventricle (Fig. 2). One-third of ependy-

omas are located supratentorially where they have aharacteristic deep parietal white matter location ratherhan intraventricular. They are slow growing tumors with anverall 60%-70% survival rate at 5 years after resection.Infratentorial ependymomas typically preset as heteroge-

-year-old boy. (A) Axial noncontrast CT image shows anding into the parietal and occipital brain parenchyma.eral ventricle. Note ventricular drainage catheter tip inth significant heterogeneous signal. Areas of dark signalconsistent with calcifications/hemorrhagic staining.enhancing mass with solid/cystic components involvingthe dural/extracranial spaces. Involvement of multipleneuroectodermal tumor (Images courtesy of Dr. Blaise

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oramina of Luschka and Magendie into the cisterns. Punc-ate calcifications occur in approximately 50% of cases,herefore CT may be helpful in differentiating this tumorrom MB and PA (Fig. 2).23 Ependymomas may also dem-nstrate cystic transformation, hemorrhage, necrosis, anddema.

horoid Plexus Papilloma/arcinoma (WHO Grade 1 and 4)horoid plexus papillomas (CPP) are intraventricular papil-

ary neoplasms that are derived from the choroid plexus ep-thelium. CPP is one of the most common brain tumors inhildren below the age of 2 years.24 In the pediatric popula-ion they are located in the atrium of the lateral ventricle. Inontrast, tumors in adults are typically located in the fourthentricle and cerebellopontine angles. CPP is a slowly grow-ng tumor with a 5-year survival rate close to 100%.

Imaging features include a frond-like lobulated mass withntense enhancement. Calcifications and hemorrhage are fre-uently present. Hydrocephalus is very commonly associatedith CPP’s and can be due to either overproduction or ob-

truction of cerebrospinal fluid (CSF).Choroid plexus carcinomas (CPC) are malignant neo-

lasms that account for approximately 20%-30% of all cho-oid plexus masses. Most cases occur in children and alsoypically arise in the lateral ventricles. CPC’s have a poorrognosis with a 50% survival rate at 5 years. Imaging find-

ngs that can help differentiate CPP from carcinomas includextension of the lesion beyond the ventricle wall, prominentasogenic edema, and mass effect.23 Both CPP’s and CPC’san seed the CSF, however metastatic spread is more com-only observed with carcinomas.

Figure 4 Dysembryoplastic neuroepithelial tumor in a 1sion recovery (FLAIR) image shows a cortical lesion ihyperintense signal. (B) Coronal T1 image with gadolini“bubbly appearance” with small rounded areas of hypoi
Dr. Blaise Jones, MD, Cincinnati Children’s Hospital).
euronal and Mixedeural-Glial Tumors (WHO Grade 1-2)ysembryoplastic neuroepithelial tumors (DNET) and gan-liogliomas/gangliocytomas are the most common mixedeural-glial tumors in children and young adults. These le-ions are cortical tumors often associated with refractory sei-ures.

DNET is a benign mixed neural-glial tumor frequentlyssociated with a background of cortical dysplasia.25 They areost commonly found in the temporal lobes; however, they

an arise in other areas of the cerebral hemispheres and pos-erior fossa. On magnetic resonance imaging (MRI), DNETsypically have a “bubbly” or multicystic appearance. Mostesions are well defined with no edema and little mass effect.nhancement is present in up to 50% of cases and is usuallyodular or ringlike in appearance. Calcification may beresent. A “FLAIR (fluid attenuated inversion recovery)right ring” sign has been described with these tumors,hich is a complete or incomplete hyperintense rim that maye caused by the presence of loose peripheral neuroglial ele-ents (Fig. 4). This sign may help differentiate these tumors

rom other cortical lesions.26

Gangliogliomas (WHO grade 1 or 2) and gangliocytomasWHO grade 1) are also cortically based neoplasms. Ganglio-liomas are composed of both benign mixed atypical gan-lion cells and neoplastic glial cells, whereas gangliocytomasre primarily composed of dysplastic or neoplastic neurons.lthough both lesions are usually benign, rare cases of ma-

ignant degeneration or metastatic spread have been repor-ed.27 These lesions can be either solid, cystic, or mixed.15

pproximately 50% will present as a cystic mass with a mural

old girl with seizures. (A) Axial fluid attenuated inver-left temporal lobe, with an incomplete medial rim ofows subtle enhancement of the cortical lesion. Note they on FLAIR and T1 near the cortex (Images courtesy of

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odule. Most lesions demonstrate either solid or heteroge-eous enhancement. Mass effect and edema are uncommon.

rainstem Tumors (WHO Grade 1-4)ost brainstem tumors are gliomas, including fibrillary as-

rocytomas, PAs, and rarely glioblastomas. Eighty percent ofll brainstem gliomas occur in the pediatric population. Theyre categorized according to where they develop (pontine,edullary, and midbrain) and whether they are diffuse or

ocal. Prognosis varies greatly depending on the location andrade of the lesion.

Pontine gliomas are more often diffuse lesions that mayresent with cranial nerve palsies and ataxia.28 These lesionsre often high-grade and have a poor long-term prognosis.maging features include expansion of the brain stem withbnormal T2 prolongation. Enhancement is usually absent.

Tectal gliomas typically have a distinctly benign behaviorompared to other brainstem tumors. Some authors believehat these tumors are hamartomas; however, other seriesave histologically shown these tumors to be low-grade PAs.ue to their location adjacent to the sylvian aqueduct, these

esions often present with obstructive hydrocephalus. Theysually do not require treatment beyond CSF diversion suchs third ventriculostomy or shunting.24

umors Moreommon in Adulthood

strocytomasliomas are the most common primary intraaxial mass indult population. Astrocytomas account for over half of allliomas and can be divided into 2 major categories, infiltra-ive and noninfiltrative. Infiltrative astrocytomas are muchore common, representing 75% of all lesions. The nonin-

Figure 5 Low-grade astrocytoma in a 35-year-old womademonstrates a moderate sized area of hyperintense sign(B) Axial T1-weighted post gadolinium image demon
enhancement is observed. Note the relative lack of mass effect
ltrative subset includes PAs, pleomorphic xanthoastrocyto-as, subependymal giant cell astrocytomas, and desmoplas-

ic cerebral astrocytomas of childhood. This section willrimarily focus on the infiltrative type.Infiltrative astrocytomas range from low-grade lesions to

ighly aggressive malignant neoplasms. Grading these tu-ors is based on several histopathologic features including

ellularity, nuclear atypia, mitotic activity, endothelial prolif-ration, and necrosis. As described previously several imag-ng features including mass effect, edema, enhancement, andecrosis can help predict tumor grade.Low grade astrocytomas (WHO grade 2) comprise approx-

mately 25% of all gliomas.29 They tend to occur in youngerdults, often in the third and fourth decades of life. Low gradeliomas are best visualized on MRI and typically present asonenhancing well demarcated or ill-defined lesions in theerebral hemispheres (Fig. 5). Edema is usually absent. Typ-cally there is absent or minimal mass effect, a finding whichan be striking given the size of some lesions.

Anaplastic astrocytomas (AA) (WHO grade 3) occur in alightly older population and confer a worse prognosis. Theedian survival rate for these patients is 2-3 years. Most AA’s

esult from dedifferentiation of low grade gliomas, howeverome arise de novo.30 Histologically, AA contains gemisto-ytes and protoplasmic elements but no necrosis. Dissemina-ion occurs through the white matter tracts. AA’s typicallyemonstrate edema and mass effect that helps to differentiatehem from low grade gliomas (Fig. 6). Approximately two-hirds of AA’s will partially enhance.

GBM (WHO grade 4) is the most aggressive and malignantorm of astrocytoma and is characterized histologically byecrosis and neovascularity. It is the second most commonumor in adults after meningioma and usually occurs in pa-ients older than 50 years of age.6,31 Involvement of patients

presented with seizures. (A) Axial T2 weighted imagelving the white matter and cortex of the left frontal lobe.subtle hypointensity within the lesion. No abnormal

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ess than 30 years is rare. These tumors have the worst prog-osis among primary brain tumors. The median postopera-ive survival time is 8 months, and the overall 10-year sur-ival rate in patients older than 45 of age is less than 1.8%.

GBM’s are most commonly located in the supratentorialhite matter. Involvement of the brainstem and cerebellum

s rare; however, these locations are more common in chil-ren than adults (Fig. 7). On MRI, GBM’s are usually identi-ed as large heterogeneously enhancing masses with signifi-ant necrosis, mass effect, and vasogenic edema (Fig. 8).

Figure 6 Anaplastic astrocytoma in a 48-year-old man wiimage shows a large lesion in the right medial occipitoparight parietal white matter and across the splenium ofimage demonstrates a nonenhancing, hypointense masstiate this lesion from a low-grade astrocytoma. One-thir

Figure 7 Glioblastoma multiforme in a 5-year-old boy wintraaxial mass centered in the right brachium pontiscomponent. (B) Axial T1 postgadolinium image show
Cerebellar and brainstem glioblastomas are rare, however they
emorrhage of differing stages is often observed. Involve-ent of the bilateral hemispheres through the corpus callo-

um (“butterfly glioma”) is a classic presentation.Surgical resection of GBM’s is nearly always incomplete

ue to the highly infiltrative nature of the tumor. Biopsiesaken from around the margins of resection cavities haveemonstrated tumor cells in the surrounding “edema” andven in normal appearing white matter.32 Surgical resec-ion and radiation are frequently targeted to the enhancinghigher grade) portion of the tumor, however the presence

al abnormalities and headaches. (A) Axial T2-weightedobes. Surrounding abnormal T2 signal extends into thepus callosum. (B) Axial T1-weighted post gadoliniumthe mass effect and midline shift that helps to differen-aplastic astrocytomas will not enhance.

ormal gait and vomiting. (A) Axial T2 image shows ana central area of necrosis and thick peripheral solidal enhancement of the thick peripheral component.

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ligodendroglioma (WHO Grade 2)ligodendrogliomas are infiltrative gliomas that originate fromligodendroglial cells. They occur in middle-aged adults andften present with seizures. Pediatric involvement is rare. Oli-odendrogliomas may be low grade (WHO grade 2) or anaplas-ic (WHO grade 3). Similar to astrocytomas, higher gradeligodendrogliomas demonstrate increased cellularity,itotic activity, endothelial hyperplasia, and necrosis. Mixed

ligodendrogliomas contain both features of astrocytomas andligodendrogliomas, and can be classified as grade 2 or 3.

Figure 9 Oligodendroglioma in a 30-year-old man who pmildly heterogeneous left frontal mass involving cortex.were confirmed on CT. The lesion is well-defined with

Figure 8 Glioblastoma multiforme in a 59-year-old manT2-weighted image demonstrates a mildly hyperintenssurrounding abnormal T2 signal in the adjacent white mT1-weighted post gadolinium image shows an irregular

gadolinium image shows patchy enhancement within the lesio

Many oligodendrogliomas demonstrate 1p and/or 19qhromosomal deletions.33 The presence of these chromo-ome losses increases the tumor’s response to radiation andhemotherapy and improves prognosis. Patients with bothp and 19q deletions have a median survival time of 8-10ears whereas patient without the deletions have a survivalime of 3-4 years.

Differentiating oligodendrogliomas from astrocytomas ononventional imaging is often not possible. However, severalmaging features favor the diagnosis of oligodendroglioma,ncluding cortical involvement, heterogeneous signal, intra-umoral cysts, patchy enhancement, and the presence of cal-ifications34,35 (Fig. 9). Calcifications, which can be seen in

with seizures. (A) Axial T2 FLAIR image shows a large,areas of hypointense signal represent calcifications thatema and mild mass effect. (B) Axial T1-weighted post

resented with seizures and neurologic deficit. (A) Axialin the lateral right frontal lobe. Note the prominent

that represents edema and infiltrative tumor. (B) Axialncing mass with areas of necrosis.

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0% of all oligodendrogliomas, are best demonstrated on CT;owever, gradient imaging can increase MR’s sensitivity. Ol-

godendrogliomas tend to have higher relative CBVs on MRerfusion studies compared to other low-grade glial tumorshat is related to a dense capillary network rather than aigher grade of tumor.13

leomorphicanthroastrocytoma (WHO Grade II)leomorphic xanthroastrocytoma (PXA) is a distinct type ofircumscribed astrocytic tumor noted for cellular pleomor-hism and xanthomatous change. Although usually classifieds WHO grade 2 tumors, they can undergo malignant trans-ormation. PXAs are slow growing lesions that typicallyresent in the first 2 decades of life. They are usually located

Figure 10 Primary central nervous system lymphoma in a(B) T2 FLAIR, and (C) post gadolinium images demoanterior genu of the corpus callosum extending into thethe corpus callosum. The lesions are mildly hyperintenedema. The multiplicity of lesions, periventricular locat
lymphoma.
n the cerebral hemispheres with a higher incidence in theemporal lobes. Recurrence after resection is uncommon andhe survival rate at 10 years is 70%.

Imaging features of PXAs typically include a supratentorialortical cystic mass with an enhancing mural node. PXAs areuperficial lesions that involve the leptomeninges as well ashe brain parenchyma. As a result, a “dural tail” may beresent that can help differentiate these neoplasms fromther cortical tumors, such as DNET or ganglioglioma.36

rimary CNS Lymphomahe vast majority of intracranial lymphomas are primary le-ions that involve the brain parenchyma. More than 90% areon-Hodgkin B-cell type. Secondary CNS lymphoma is rare

rs-old immunocompetent man. (A) Axial T2-weighted,an irregular, homogeneously enhancing mass in the

l lobes. An additional lesion is noted in the splenium ofT2 weighted images and are associated with moderated homogeneous enhancement support the diagnosis of

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nd often presents with dural or leptomeningeal involve-ent.Imaging features and clinical prognosis of primary CNS

ymphoma vary with the patient’s immune status. In immu-ocompetent patients primary lymphoma typically presentss solitary or multiple predominantly solid masses in theasal ganglia and white matter, often periventricular in loca-ion.37 These are highly cellular tumors that give them a char-cteristic hyperdensity on CT and homogeneous hypointen-ity on T2 with strong homogeneous enhancement38 (Fig.0). Diffusion restriction may be present due to the denseellularity of the lesion.39 The administration of corticoste-oids can modify or annul tumor enhancement, and thereforehould not be administered before initial CT and MR imagingnless clinically necessary.In immunodeficient patients, CNS lymphoma tends to

resent as multifocal heterogeneous/peripheral enhancing le-ions with central necrosis.40 These lesions may be indistin-uishable from infectious etiologies including toxoplasmosis.owever, as in immunocompetent patients, lymphoma inatients with acquired immunodeficiency syndrome (AIDS)as a characteristic tendency to involve the ependymal sur-aces and periventricular white matter.

The incidence of primary CNS lymphoma has tripled overhe past 2 decades, largely due to the increase in patients withIDS. However, the incidence of lymphoma is also rising in

he immunocompetent population.38 No environmental orehavioral factors have been identified to account for this rate

ncrease.41 In general the prognosis for CNS lymphoma isoor due to recurrent disease, however it is moderately better

n immunocompetent patients. The median survival time forIDS patients with intracranial lymphoma is only 2-6onths.

emangioblastoma (WHO Grade 1)emangioblastomas are benign tumors of vascular etiology

hat represent approximately 1%-2% of all primary CNS neo-

Figure 11 Hemangioblastoma in a 43-year-old man whogadolinium T1-weighted images demonstrate a large cys
lum. Marked compression of the fourth ventricle is present.
lasms. Although rare, hemanagioblastomas are the mostommon primary adult intraaxial posterior fossa tumor.42

ver 85% of hemangioblastomas occur in the cerebellaremispheres. Less commonly they involve the vermis, me-ulla, and spinal cord; rare supratentorial lesions have beeneported. Males are more commonly affected than women,nd most patients present within the third to fifth decades ofife. Pediatric involvement is rare.

Most hemangioblastomas occur sporadically, however ap-roximately 25% are associated with von Hippel-Lindau syn-rome, an autosomal dominant disease which is also associ-ted with retinal angiomatosis and visceral tumors involvinghe kidneys and adrenal glands.43 Surgical resection is usuallyurative, however patients with von Hippel-Lindau syn-rome often have multiple lesions.The most common imaging presentation of hemangioblas-

omas is a well-defined cyst of variable size with an intenselynhancing mural nodule (Fig. 11). Approximately 25% ofesions will present as a solid mass without a defined cyst.rominent flow voids may be present within the solid por-ions of the tumor due to the vascular nature of the tumor.ncommonly, hemangioblastomas can present as a cystithout evidence of an enhancing nodule or wall.

eningioma (WHO Grade 1-3)eningiomas arise from arachnoid meningothelial cells and

re the most common benign intracranial neoplasm in adults.n general, these lesions are slow growing tumors (WHOrade 1) with a good prognosis, however atypical and ana-lastic meningiomas (WHO grade 2–3) do occur.44 Aggres-ive meningiomas can invade the brain parenchyma and willarely metastasize to distal sites.

The incidence of meningiomas is highest in middle-agedomen. Meningiomas may occur in multiples, particularlyhen associated with neurofibromatosis type 2, and haveeen associated with a history of radiation treatment. The

ted with headaches. (A, B) Axial T2-weighted and postss with an enhancing mural nodule in the right cerebel-

presentic ma

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ost common location for meningiomas is in the cerebralonvexities. Less common locations include the sphenoididge, olfactory groove, parasellar region, cerebellopontinengle, and optic nerves. Intraventricular lesions in the adultopulation are rare but have a typical presentation in the atriaf the lateral ventricles (Fig. 12).Meningiomas are most commonly present as extraaxialasses with prominent homogeneous enhancement and

road dural attachments. Although the MR signal charac-eristics of meningiomas on precontrast sequences canary, typically they are isointense to brain on T1 weightedmages and isotense to mildly hyperintense on T2eighted images. This is due to the homogeneous cellu-

arity of the tumor. Tumoral calcifications and hyperosto-

Figure 12 Intraventricular meningioma in a 46-year-oldweighted images demonstrate an intraventricular masshyperintense on the T2 weighted image and isointense ohomogeneous enhancement of the mass. The signal cha
an intraventricular meningioma.
is of the underlying skull bone are frequent. Edema isommonly observed in the adjacent brain parenchymaarticularly with masses over the cerebral hemispheres.he cause of the edema is not fully understood and may beelated to mechanical compression or secretions from theumor, however there is no direct correlation between theresence of edema and the aggressiveness of the lesion orrain invasion.45 Lesions that can mimic meningiomas in-lude dural metastases, lymphoma, and hemangiopericy-omas.

Meningiomas in the pediatric population are rare, howeverhen they occur they often have distinct characteristics.hildhood meningiomas have a male predilection, are moreommonly intraventricular in location compared to adults

n with headaches. (A) Precontrast axial T2 and (B) T1the atrium of the right lateral ventricle. The lesion is

C) Post gadolinium T1-weighted image shows marked,stics, location, and enhancement pattern are typical for

womawithinn T1. (racteri

aa

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pdthc

g

(Su

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nd usually do not have a dural tail.46 These tumors also havetendency to malignant transformation.

entral Neurocytoma (WHO Grade 2)entral neurocytoma is an intraventricular neuronal cell tumor

hat typically arises from the septum pellucidum or ventricularall. Most lesions are present in the lateral ventricles, however

hird ventricular involvement does occur. Histologically, centraleurocytomas resemble oligodendrogliomas, and until recentlyere considered “intraventricular oligodendrogliomas.” Neuro-al characteristics observed on electron microscopy led to theeclassification of this lesion in 1982.47

Central neurocytomas occur in young adults and oftenresent with signs of increased intracranial pressure or hy-rocephalus due to their intraventricular location. The lesionypically has a benign course, however more aggressive be-avior including invasion of the brain and seeding of the CSFan occur. The survival rate is approximately 81% at 5 years.

On imaging, central neurocytomas are present as hetero-eneous masses often attached to the septum pellucidum

Figure 13 Central neurocytoma in a 39-year-old man witscan demonstrates a large heterogeneous, mildly hyperpellucidum. (B) T2-weighted sagittal image shows prom(C) T1-weighted post gadolinium coronal image dem
dilatation caused by obstruction at the foramen of Monro.
Fig. 13). Calcifications and cystic changes are common.48

olid portions of the tumors demonstrate variable and irreg-lar enhancement.

ubependymoma (WHO Grade 1)ubependymoma is an uncommon, benign intraventricu-ar tumor that typically occurs in middle-aged to olderdults. The most common location for this tumor is thenferior fourth ventricle followed by the frontal horns ofhe lateral ventricles attached to the septum pellucidum.ubependymomas are usually asymptomatic, however ob-tructive hydrocephalus can occur due to the lesion’s in-raventricular location.49 Patients with subependymomasave an excellent prognosis; surgical resection is curative

n most cases.Imaging features of subependymomas on CT include a

ypodense lobular mass within the fourth or lateral ventri-les. On MR these lesions are usually hypo-to isointense on1 weighted images and hyperintense on T2 weighted se-uences. Enhancement is typically absent (Fig. 14).

of increased intracranial pressure. (A) Noncontrast CTintraventricular mass with involvement of the septumheterogeneity of the lesion with multiple small cysts.

tes patchy enhancement. Note the lateral ventricular

h signsdenseinent

onstra

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R

1

1

1

1

1

1

1

1

1

1

2

2

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onclusionmaging is a vital step in the initial work-up of brain tumors.n appropriate differential diagnosis should be based notnly on the radiographic characteristics of the tumor but alson the age of the patient, location of the lesion, and theumor’s relative frequency. Advanced imaging techniques of-en can provide complementary information; however, con-entional CT and MRI remain the primary tools for neuro-ncological diagnosis and early detection.

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Imaging of Common Adult and Pediatric Primary Brain Tumors€¦ · Imaging of Common Adult and Pediatric Primary Brain Tumors ... The review will focus on the initial imaging diagnostic