ITMIG classification posterior mediastinal masses.pdf

Radiology itmig classification and posterior mediastinal masses

1. ITMIG Classification and
Posterior mediastinal masses

2. •InternationalThymicMalignancyInterestGroup(ITMIG)classificationofmediastinalcompartments-
reflectsdivisionofthemediastinumbasedoncross-sectionalimaging.
•Toconsolidatepriordiscrepantclassificationsystemsinusebydifferentmedicalspecialties.
•Aworkinggroupcomposedofapproximately225expertsinthoracicsurgery,medicaloncology,diagnostic
radiology,andpathology-anatomicclassificationwhichunifiedthevarioussystems.

3. •The ITMIG classification divides themediastinuminto three compartments: pre-vascular, visceral and
paravertebral.
•Pre-vascular compartment
•Boundaries
•superior:thoracic inlet
•inferior:diaphragm
•anterior: posterior cortex of thesternum
•lateral: parietal mediastinalpleura
•posterior: anterior aspect of thepericardium
•Contents
•thymus
•lymph nodes
•leftbrachiocephalic vein
•fat

4. •Visceral compartment
•Boundaries
•superior: thoracic inlet
•inferior: diaphragm
•anterior: posterior boundary of the pre-vascular compartment
•posterior: a vertical line connecting a point on each thoracic vertebral body 1 cm posterior to its anterior
margin (visceral-paravertebral compartment boundary line)
•Contents
•trachea/carina
•oesophagus
•lymph nodes
•heart
•ascending aorta;aortic arch;descending thoracic aorta
•superior vena cava
•intrapericardialpulmonary arteries
•thoracic duct

5. •Paravertebral compartment
•Boundaries
•superior: thoracic inlet
•inferior: diaphragm
•anterior: posterior boundaries of the visceral compartment
•posterolateral: vertical line against the posterior margin of the chest wall at the lateral
margin of the thoracic spine
•Contents
•thoracic spine and paravertebral soft tissues

6. •Most abnormalities in this region are neurogenic neoplasms that arise from the dorsal root ganglia/ neurons
adjacent to the intervertebral foramina.
•Otherpotentiallesionsinthiscompartmentareofinfectious(discitis/osteomyelitis)ortraumatic(hematoma)
origin,ormiscellaneouslesionsrelatedtootherunderlyingconditions(suchasextramedullary
haematopoiesis).

7. •ITMIG definition of mediastinal compartments.
Sagittal reformatted multidetector CT image (a)
and axial multidetector CT images at the levels
of the aortic arch (b), left pulmonary artery (c),
and left atrium (d)
•Note that the prevascularcompartment (purple)
wraps around the heartandpericardium, which
are located in the visceral compartment (blue).
•Yellow = paravertebral compartment,
•green line = visceral-paravertebral compartment
boundary line.

8. Localization of Mediastinal Abnormalities
•Two tools have been described by ITMIG and are recommended to help identify the compartment from which
these lesions originate.
•“Center method” and states that the center of a mediastinal lesion, defined as the center point of the lesion on
the axial CT image that demonstrates the largest size of the abnormality, localizes the lesion to a specific
mediastinal compartment
•“Structure displacement tool” and is useful in scenarios in which very large mediastinal lesions displace
organs from other mediastinal compartments, typically those that abut the compartment from which the lesion
originated

9. Approach to the Paravertebral Compartment
•Astheparavertebralcompartmentincludesthethoracicspineandparavertebralsofttissues,most-neoplasms
ofneurogenicorigin.
•Otherlesscommonneoplasticconditions-lymphoma,primaryosseoustumors,andmetastases.
•Nonneoplasticcauses-thoracicspinalinfectionsduetobacterialandmycobacterialagents,cysticlesions
suchasthoracicmeningoceleandneurentericcyst,andextramedullaryhematopoiesis.
•Theapproach-basedprimarilyonthecompositionofthemediastinalabnormality.
•Whilespecificmassesmaybeincludedinthedifferentialdiagnosisonthebasisofimagingfeatures,clinical
informationisnecessaryinmostcases.
Lesions Fluid Fat Vascular
Posterior Neurogenic
Bone and marrow
Infection
Hemorrhage
Lung ca
Neuroentericcyst
Schwannoma
Meningocele
Cystic LAP
Lymphangioma
Extramedullary
hematopoiesis
Liposarcoma
DescAorta
Hemangioma

10. Role of X ray
•CXR -first step , Findings that help in localisingthe lesion to the mediastinum include:
•1. No air bronchogram
•2. Obtuse margins with the lung
•3. Distortion, obliteration or thickening of mediastinal lines(posterior junctional line, paraspinal line,
azygoesophagealline)
•4. Abnormalities of spine

11. •Disruption of the azygo-oesophagealrecess can
be caused by disease in either the middle or
posterior mediastinum.
•Paravertebral masses disrupt the paraspinal
lines, and the region of masses above the level
clavicles can be inferred by their lateral
margins.
•Posterior masses have sharp margins caused by
their interface with lung, whereas anterior
masses do not.

15. Cervicothoracic sign
•The anterior mediastinum stops at
the level of the superior clavicle.
•Therefore, when a mass extends
above the superior clavicle, it is
located either in the neck or in the
posterior mediastinum.
•When lung tissue comes between
the mass and the neck, the mass is
probably in the posterior
mediastinum.

17. Soft-Tissue Lesions-Neurogenic Neoplasms
•Neurogenicneoplasms,70%–80%ofwhicharebenign,arethemostcommoncauseofparavertebral
compartmentmassesandaccountfor20%and35%ofalladultandpediatricmediastinalneoplasms,
respectively
•From nerve sheath -neurofibroma, schwannoma, malignant tumor of nerve sheath
•From sympathetic ganglia -ganglioneuroma, ganglioneuroblastomaand neuro-blastoma
•From neuroectodermal cells located in relation to ANS-paraganglioma and pheochromocytoma

18. •Whenasmooth,round,orovalmassispresentintheparavertebralregionatmultidetectorCT,themost
likelydiagnosisisaneurogenicneoplasm,typicallyabenignperipheralnervesheathtumorsuchas
schwannomaorneurofibroma.
•Peripheralnervesheathneoplasms-fromspinalorproximalintercostalnerves,lesscommonly-vagus,
RLN,orphrenicnerves,andaccountfor70%ofmediastinalneurogenictumors.
•AtmultidetectorCT,peripheralnervesheathneoplasms-adumbbellmorphologyandcommunication
withthespinalcanal.
•Heterogeneity-cysticchanges/hemorrhage-morecommoninschwannomasthaninneurofibromas

20. •39-year-oldasymptomaticwoman.Coned-downaxial
multidetectorCECTimageattheleveloftheaorticarch
showsawell-definedheterogeneoussofttissuemass
(arrow)intherightparavertebralmediastinum,compatible
withabenignperipheralnervesheathtumor,inthiscasea
schwannoma.
•Whenasmooth,round,orovalmassispresentinthe
paravertebralregionatmultidetectorCT,themostlikely
diagnosisisaneurogenicneoplasm,typicallyabenign
peripheralnervesheathtumorarisingfromspinalor
intercostalnerves.
•Asinthiscase,internalheterogeneitymaybeduetocystic
changesorhemorrhageandismorecommonin
schwannomasthaninneurofibromas.

21. •Neurogenicneoplasms-benignpressureerosionofadjacentribsorvertebraeandenlargementoftheneural
foramina.
•Thesefindingsaresuggestiveofabenignlesion,comparedwiththeosseousinvasionanddestructiontypical
ofmalignancies.
•MRimagingoptimallydemonstratestheextentofintraspinal/extraduralextension.
•The“fascicularsign”describesmultiplehypointense,small,ring-likestructurescorrespondingtofascicular
bundlesandistypicallyassociatedwithschwannomas.
•The“targetsign”ischaracterizedbycentrallowsignalintensityandsurroundingperipheralhighsignal
intensityandismorecommonlyseenwithneurofibromasthanwithschwannomas.

23. •Previouslystableneurofibroma–suddenincreaseinsize,developsregionsofheterogeneity,and/orinvades
adjacenttissues,malignanttransformationtoamalignantperipheralnervesheathtumor
•InNFtype1-10%lifetimeriskofdevelopingamalignantperipheralnervesheathneoplasm-accountformost
cancer-relateddeathsinthesepatients.
•FDGPET/CThasdemonstratedutilityindistinguishingmalignantperipheralnervesheathtumorsfrom
benignneurofibromas,withsensitivityof95%andspecificityof72%.
•Anotherstudyrevealedsensitivityof97%andspecificityof87%fordetectionofmalignantperipheralnerve
sheathtumorsandsuggestedthatlesionswithSUVmaxlessthan2.5shouldbeconsideredbenign,thosewith
SUVmaxgreaterthan3.5shouldbeconsideredmalignant,
•ThosewithSUVmaxof2.5–3.5shouldbefollowedwithsurveillanceimaging

24. Peripheral Nerve Tumors
commonly in adults
no sex predilection.
•Most -asymptomatic ,incidentally on chest radiograph.
•Usually arise from intercostal nerves close to the spine, near the junction of vertebral body with adjacent rib
and may extend through neural foramina into spinal canal (dumb-bell tumor).
•More than 1/3rd of patients with neurofibromas may have neurofibromatosis type I (von Recklinghausen's
disease).
•The plexiform neurofibroma infiltrates along the nerve trunk or plexuses.
•Schwannoma-contain areas of cystic degeneration, hemorrhage and calcification

28. •Malignantperipheralnervesheathtumorina37-year-oldwomanwithneurofibromatosistype1.
•(a)Coned-downaxialnonenhancedmultidetectorCTimageofthelowerthoracicspineshowsawell-
circumscribedhomogeneoussoft-tissuemass(arrow)intheleftparavertebralregion,compatiblewitha
biopsy-provenbenignperipheralnervesheathneoplasm.
•Notethebenignpressureerosionexertedonthevertebralbody,whichfurthersupportsthediagnosis.
•(b)Coned-downaxialFDGPET/CTimage2yearslatershowsmarkedintervalincreaseinthesizeofthe
lesion,whichdemonstratesincreasedFDGuptakeandinvasionanddestructionofthethoracicspine,left
lowerlobe,andchestwall—incontrasttothebenignpressureerosionseenearlier—findingsconsistentwith
malignancy.
•Findingssuggestiveofmalignantdegenerationofaneurofibromaincludesuddenincreaseinsize,
developmentofinternalregionsofheterogeneity,invasionofadjacentstructures,andincreasedFDGuptake
atPET/CT.

29. Others
•Sympatheticganglionneoplasmssuchasganglioneuromas(benign),ganglioneuroblastomas,and
neuroblastomas(malignant)
• tumorsofchildhood
• mediastinumisthe2ndM.C.siteforthesetumors,theadrenalbeingtheM.C.site
•Neuroendocrineneoplasm-paragangliomasandaremuchlesscommon.
•Theimagingfeatures-areoftennonspecific,andhistologicsamplingisoftennecessaryfordiagnosis.
•Thepresenceofintensehomogeneousenhancementinaparavertebralmassshouldraisesuspicionfora
paraganglioma.

30. •Well-defined with smooth or lobulated outline located in the posterior mediastinum.
•Gangloineuromaand ganglioneuroblastomausually extend vertically over 3-5vertebrae lateral to the spine,
may show broad base on the spine and cause pressure erosion of adjacent vertebra.
•CT shows homogeneous attenuation whereas MRI shows homogeneous and intermediate SI on both T1W and
T2W images.
•10% of neuroblastoma -stippled calcification -can be seen on CXR. Evidence of widespread local invasion
with tendency to cross midline, is characteristic of neuroblastoma.
•CT shows paraspinal mass with heterogeneous soft tissue attenuation because of hemorrhage, necrosis, cystic
degeneration and calcification.
•MRI shows heterogeneous SIon all pulse sequences and heterogeneous enhancement with gadolinium.
•MIBG scintigraphy -for imaging , especially to assess the extent of disease. 30% neuroblastomas are not
MIBG avid.

31. Paraganglioma
•Paraganglioma (chemodectoma) -tumor originating from neuroectodermal cells located in relation to ANS,
especially in the region of the AP window and the posterior mediastinum.
•Paraganglioma -round, extremely vascular soft tissue mass that enhances markedly on CECT.
•hypointense on T1W and hyperintense on T2W images, with flow voids within, indicating hypervascular
nature.
•Arteriography-large feeding vessels, pathologic vessels and intense tumor blush.
•MIBG scintigraphy shows increased activity, good technique to demonstrate paragangliomas.
•MRI has largely replaced CT as an initial imaging modality in the evaluation of patients with suspected
neurogenic tumors. Unfortunately, MRI is no more specific than CT in differentiating benign from malignant
lesions.

33. Soft-Tissue Lesions-Extramedullary Hematopoiesis
•Inthesettingofparavertebralmassesadjacenttothoracicvertebraeand/orribsatmultidetectorCTina
patientwithimagingandclinicalevidenceofahematologicdisorderresultinginbonemarrowreplacement
(myelofibrosisorchronicmyelogenousleukemia)orhemolyticanemia(thalassemia,sicklecellanemia,or
hereditaryspherocytosis),extramedullaryhematopoiesisshouldbestronglyconsidered.
•Thesemassesmaybelargeorsmallandunilateralorbilateralandtypicallyenhanceafteradministrationof
intravenouscontrastmaterialduetohighvascularity.
•Heterogeneousattenuationand/orenhancementmaybeseeninthesettingofirondepositionandfat
infiltrationinlong-standinglesions
•Intheabsenceofspecificosseousfindingssuggestinganunderlyinghematologicdisorder,functionalimaging
with99mTcsulfurcolloidbonemarrowscanningandSPECT/CTbonemarrowscanningmaynoninvasively
confirmthepresenceoffunctioninghematopoietictissue,thusavoidingbiopsy.
•Inpatientswithsicklecelldisease,theancillaryfindingofautosplenectomyservesasacluetothediagnosis
ofextramedullaryhematopoiesis.

34. •(a)Extramedullaryhematopoiesisina51-year-
oldmanwithmyelofibrosis.
•Coned-downcoronalnonenhancedmultidetector
CTimagethroughthethoracicspineshows
numerousparavertebralsoft-tissuenodulesand
masses (arrows),compatiblewith
extramedullaryhematopoiesis.
•(b)Extramedullaryhematopoiesisina62-year-
oldwomanwithbonemarrowreplacementdue
toachronicmyeloidneoplasm.
•Coned-down axial contrast-enhanced
multidetectorCTimageattheleveloftheaortic
archshows multipleheterogeneous
paravertebralmasses(M)composedofbothfat
andsofttissue,whichischaracteristicof
extramedullaryhematopoiesis.
•Notetheexpansionofthemarrowspacesofthe
ribsandvertebralbodies(*),supportingthe
diagnosis.
•AtmultidetectorCT,thelesionsof
extramedullaryhematopoiesismayappearas
soft-tissuelesionsthatenhanceafter
administrationofintravenouscontrastmaterial
duetohighvascularityorheterogeneousmasses
duetoirondepositionandfatinfiltrationinlong-
standingdisease.

35. Cystic Lesions-Intrathoracic Meningocele
•WhenasmoothandunilocularmasswithfluidattenuationatmultidetectorCTispresentintheparavertebral
mediastinumandisassociatedwithvertebralanomaliessuchashemivertebrae,butterflyvertebra,orspina
bifida,thelikelydiagnosisisanintrathoracicmeningocele.
•Anintrathoracicmeningocele-anomalousherniationoftheleptomeningesthroughanintervertebralforamen
orvertebralbodydefectandismorecommoninadultsthaninchildren
•Associatedfindings-enlargementofintervertebralforaminaandvertebraland/orribanomaliesor
scoliosis
•backpain,neurologicaland/orrespiratorysymptoms
•Difficulttodistinguishintrathoracicmeningocelesfromotherlowattenuationparavertebralmassessuchas
neurentericcystsorneurogenicneoplasms,theclinicalsettingofneurofibromatosistype1(85%)should
clinchthediagnosis.
•However,inuncertaincases,multidetectorCT,MRimaging,ormyelographyperformedafterintraspinal
injectionofcontrastmaterialwillrevealfillingofthemeningocele

36. •Intrathoracic meningocele in a 49-year-old
woman with neurofibromatosis type 1.
•(a) Coned-downaxial contrast-enhanced
multidetector CT image at the level of the
aortic arch shows a large fluid attenuation
mass (M) in the posterior right hemithorax
that communicates with the spinal canal.
•Note the irregularity of the adjacent
vertebral body and expansion of the spinal
canal.
•(b) Coned-down axial contrast-enhanced
multidetector CT image at the level of the
kidneys shows multiple cutaneous
neurofibromas (arrows).
•When a homogeneous low-attenuation
paravertebral mass is present in a patient
with neurofibromatosis type 1 and
associated with vertebral anomalies such
as hemivertebrae, butterfly vertebra, or
spina bifida, a definitive diagnosis of
intrathoracic meningocele can be made.

37. Cystic Lesions-Mediastinal abscess
•Mediastinal abscess should be considered when a low-attenuation mass is identified at multidetector CT in a
patient after surgery or esophageal perforation or in the setting of infection in the adjacent thorax.
•Internal foci of air may be present, and communication may be seen with coexisting subphrenic abscesses or
empyema.
•In the majority of situations, the clinical context permits definitive diagnosis; however, in selected cases,
percutaneous needle aspiration may be necessary to differentiate between abscess and postoperative seroma or
hematoma.

38. Cystic Lesions-Pancreatic Pseudocyst
•Acysticmassintheparavertebralmediastinumthatdevelopsoverashortperiodoftimeintheclinicalsetting
ofpancreatitismayrepresentintrathoracicextensionofapancreaticpseudocyst.
•Uncommonlesions-containpancreaticsecretions,blood,andnecroticmaterialandspreadthroughthe
esophagealoraortichiatus.
•AtmultidetectorCT:thin-walledmasses-isoattenuatingorhyperattenuatingdependingonthepresenceof
hemorrhageorinfection.
•Separateintra-abdominalpseudocysts+/-.

39. Spinal infections
•Whenill-definedsofttissue,unorganizedfluid,and/oraloculatedcollectionarepresentintheparavertebral
compartmentinapatientwithclinicalsymptomssuchasbackpain,fever,andmalaise,spinalinfection
shouldbeincludedinthedifferentialdiagnosis.
•Theseinfectionsaretypicallyduetobacterialorganisms,andsignificantriskfactorsincludediabetes,
autoimmunediseases,malignancy,immunosuppression,andintravenousdruguse.
•EarlymultidetectorCTfindingsincludeparavertebralfatinfiltrationandintervertebraldiskhypoattenuation,
whereasosseouserosion,diskspacenarrowing,andsequestrumformationmaybepresentinlaterstages

40. •Discitis/osteomyelitisina62-year-
oldwoman.
•Coned-downaxialnonenhanced
multidetectorCTimage(soft-tissue
[a]andbone[b]windows)ofthe
lowerthoracicspineshows
paravertebralsofttissue(arrowsina)
andextensiveosseousdestruction.
•Theclinicalpresentationwas
significantformethicillin-resistant
Staphylococcusaureus(MRSA)
bacteremiaandbackpain.
•Thecombinationofimagingfeatures
andclinicalfindingsenables
definitivediagnosisofspinal
infection,whichmaymanifestat
multidetectorCTasill-definedsoft
tissue,unorganizedfluid,and/ora
loculatedfluidcollection.

41. •Inthesettingofimmunodeficiency,particularlyHIVinfection-tuberculousinvolvementofthespineshould
beconsidered.
•Upto60%ofHIV-positivepatientswithTBhaveskeletalinvolvement,andthespineisthemostcommonly
affectedsite,involvedinapproximately50%ofcases.
•Tuberculosisassociatedwithinvolvementoftheposteriorelements,thepresenceofalargeprevertebraland
paravertebralsoft-tissuecomponentoutofproportiontothedegreeofosseousdestruction,anddiskspace
narrowingenabledifferentiationoftuberculousfrompyogenicinfection.
•Additionally,thepresenceofcalcificationwithoutnewboneformationorsclerosisstronglysuggeststhe
diagnosisofPottdiseaseofthespine