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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_2821_Библиотеки_им_академика_М_И_Перельмана
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availableintertiarymedicalcenters,itisnowmorewidelyavailable.Thehighsuccessrate
combined with the extremely low rate of complications strongly favors this technique.
Recurrence of pain can be treated with repeat radiofrequency ablation or open surgical
removalofthelesion.
Radiothermal ablationcan be difficultinthe smaller bones because of difficulties with
targetingthelesionintheCTscanner.Inaddition,whenthelesionisinasmallbone,thereis
risk ofdamagetonearbytendons orneurovascular structures. For superficial lesionsinthe
forefoot,opensurgeryisstillthepreferredtreatment.Thesurgeonneedstobeabletolocate
thenidususingradiographs,anatomiclandmarks,anddirectobservation.Othertechniquesfor
locatingthenidushavebeendescribed.Thesurroundingreactivebonecanbeextremelydense,
anditmayalso be hypervascular and somewhatporous.Itis essential to remove the entire
nidus because failure to do so will lead to recurrence. Surgical removal often leads to
weakening oftheaffectedbone,andbonegrafting,plating,andprolongednonweight-bearing
withactivityrestrictionsmaybenecessary.
Osteoblastoma
IntroductionandDefinition
Osteoblastomaisasolitary,benignbone-formingtumorthatoccursintheposteriorelementsof
the spineand long bonesofyoungadults.The bonesofthe footare thethird mostcommon
location of this tumor, accounting for 12% of all osteoblastomas in one series.66 Although
osteoblastomaandosteoidosteomaarehistologicallyquitesimilar,thesetwotumorsarevery
differentintheirpresentation,localization,radiographicappearance,treatment,andpotential
forrecurrence.
IncidenceandDemographics
The tumor most commonly occurs in the dorsal aspect of the vertebrae, the metaphysis or
diaphysisoflongbones,andrarelyinthepelvis.Inthespine,thetumorisusuallylocatedin
theposteriorprocesseswhilethevertebralbodiesarespared.Also,thoughtumorfrequencyis
lowerinthethoracicregion ofthespine,ithasgreaterandequaloccurrenceinthecervical
andlumbar regions. Thefoot is thethird most common locationofosteoblastoma after the
spineandthefemur;12.5%ofosteoblastomasoccurinthebonesofthefoot.Mostoccurinthe
hind foot, andthe talus is the most commonly affected bone. Osteoblastoma predominantly
affectsyoungadults.Thepeakageofoccurrenceis approximately age20, though thetumor
maypresentasearlyasage10toaslateas age60.Themeanageofthepatientisabout22
years.
SymptomsandPresentation
Commonsymptomsarepainoflongduration,swelling,andtenderness. Tumors ofthespine
cancause scoliosis andneurologicsymptoms. Spinal lesions may present with myelopathic
and/orradicularsymptoms.
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X-rayAppearanceandAdvancedImagingFindings
On X-ray, osteoblastomas appear as a radiolucent defect with a central density due to
ossification. The lesion is well circumscribed and may have a surrounding sclerosis. The
tumordemonstratesincreasedisotopeuptakeonbonescan.
DifferentialDiagnosis
Thedifferentialdiagnosisofosteoblastomaincludesosteoidosteoma,osteosarcoma,giantcell
tumor,andABC.
HistopathologyFindings
On gross examination,osteoblastomas are red to tanin color withhemorrhagic areas. The
compacttissueisgranular,friable,andgritty.Hyperemiaisparticularlyevidentinthespongy
boneofvertebrae,ribs, andthepelvis. Theclassic microscopic findingofosteoblastoma is
irregular spiculesofmineralizedbone andeosinophilic osteoid rimmed byosteoblasts.The
vascular stromaischaracterizedbypleomorphicspindlecells. Thetumorcellsdifferentiate
into osteoblasts, which make varying amounts of osteoid and woven bone. Cartilage
production is a very rare finding in an osteoblastoma and should raise the suspicion of
osteosarcoma.
TreatmentOptionsforThisTumor
Usually, a biopsy is performed to confirm the diagnosis. Surgical resection by curettage,
intralesional excision, or en bloc excision are all treatment options depending on the site.
Recurrenceaftersurgeryisapproximately10%to15%.Bonegraftingiscommonlyusedafter
curettageoftheselesions,butcompletehealingmaystilloccurwithoutbonegrafting.
Thereremainssomeconcernformalignantdegenerationofosteoblastomabecauseofafew
publishedreportsofmalignantsarcomasarisinginosteoblastoma.Inaddition,asubsetofthese
tumorscanbehaveinamuchmorelocallyaggressivefashion.Thesetumorshavebeenfoundto
belargerandoccurinslightlyolderindividuals.Microscopically,thismoreaggressivevariant
of osteoblastoma may have a distinct appearance, including epithelioid features and larger
osteoblasts with abundant eosinophilic cytoplasm and vesicular nuclei. There is a lack of
consensus as to whathistologic characteristics are associated with more or less aggressive
behavior.66 These tumors have been variously termed “aggressive osteoblastoma” or
“malignantosteoblastoma.”Theradiographicandpathologicfeaturesofthesetumorsoverlap
withosteosarcoma.Inonereviewof41osteoblastomasinthefoot,2evolvedintomalignant
sarcomas.
PreferredMarginforThisTumor
Marginsshouldbeaswideaspossiblewithoutfunctionalsacrifice.
SpecialandUnusualFeatures
Osteoidosteomaandosteoblastomacanbedifferentiatedbecausetheformercausespersistent
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nocturnalpainand thelattercausesinconsistent pain.The former is less than1 cm andthe
lattergreaterthan2cm.
Chondroblastoma
IntroductionandDefinition
Chondroblastoma is a rare, benign tumor derived from chondroblasts. It is found in the
epiphysis oflong bones,usuallyofthe lowerextremity.The mostcommonsite is thedistal
femurfollowedbytheproximalfemur,proximalhumerus,andproximaltibia.Thisisoneofa
very few lesions that occur primarily in the epiphysis. Others include clear cell
chondrosarcoma and osteomyelitis. In addition, very rare cases of metastasis of
chondroblastomatothelungshavebeenreported.
IncidenceandDemographics
Chondroblastomaaccountsfor approximately1%ofbenign bonetumors,butaround10%to
15%oftheseraretumorsoccurinthebonesofthefoot.Thetumorismuchmorecommonin
males thanfemales, andthe mean ageofpresentation is approximately20years. Males are
affectedfivetosixtimesascommonlyasfemales.Theaverageageatpresentationinthefoot
isaround25years,significantlyolderthantheaverageageinotherpartsoftheskeleton.Inthe
foot,chondroblastomaismostcommonlylocatedintheposteriorsubchondralsurfacesofthe
talusandcalcaneus,inthecalcanealapophysis,andinthemidtarsalbones.
SymptomsandPresentation
Patientscomplainofpainwithor without a mass nearajoint.Thepaincanbesevere. The
nearbyjointmaybelocallyinflamed.ThereispoorresponsetoNSAIDs.Eventually,amass
appears.
X-rayAppearanceandAdvancedImagingFindings
The diagnosis of chondroblastoma can usually be made by radiograph when the age of the
patientandlocationofthelesionareconsidered.Themostcommonsiteforchondroblastoma
istheepiphysis.Thelesionislyticwithwell-definedmarginsandcanbefrom1 to6cmin
size. Scalloping or expansion of cortical bone may be present. Fine calcifications, either
punctateorinrings,maybevisible.Inthefootandankle,thelesionislocatedexclusivelyin
theepiphysis,althoughinthesmallbonesofthefootthelocationoftheepiphysismaynotbe
obvious.The lesionsappear well defined,expansile, andlucent, andtheremaybestippled
calcification or there may be no matrix mineralization. Cystic features are seen in
approximately half the chondroblastomas of the foot bones. The tumor is adjacent to an
articular surface or an apophysis. Chondroblastoma in the foot most commonly occurs in
subchondralareasofthetalusandcalcaneusaswellasthecalcanealapophysis.
CTscanisusefulfordefiningtherelationshipofthetumortothejointandtheintegrityof
theunderlyingboneandtoidentifyintralesionalcalcifications.Cystsarepresentabout20%of
thetime,andbothMRIandCTcandefinethefluidlevels.
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DifferentialDiagnosis
Thedifferentialdiagnosisincludesenchondroma,centralchondrosarcoma,andABC.
PreferredBiopsyTechniqueforThisTumor
Incisional,maybecombinedwithexcisioninselectedcases.
HistopathologyFindings
On gross examination, a chondroblastoma has a lobulated, round form and is made up of
friable,soft,grayish-pinktissuethatmaybegritty.Ifpresent,thecysticfluidisrustorstraw
colored. Chondroblastoma is made upofuniform,polygonal cells that are closely packed.
These primitive cells are derived from the epiphyseal cartilage plate and have abundant
cytoplasm.Thesecellshaveoval-shapednucleiwithaprominentgroovethathasbeenlikened
toacoffeebean.Thereislittlemitoticactivity.Ascantchondroidmatrixmaybesuperimposed
by a pericellular deposit of calcification that appears like “chicken wire.” The rapid
proliferation of immature chondrocytes does not create lacunae or formal cartilage matrix.
Giantcellsareoftenpresent.
TreatmentOptionsforThisTumor
Treatmentoftheprimarylesionconsistsofcompletecurettageandbonegrafting.Extendingthe
zone of the curettage by removing two or three additional millimeters of bone using a
mechanicalburr,orbyplacingphenolorliquidnitrogeninthetumorcavityhasbeenproposed
as a method to reduce the risk of local recurrence. Because of the risk of recurrence and
associatedfunctionalloss,theinitialcurettageshouldbeasmeticulousasnecessarytoensure
complete removal of the lesion. The surgical approach chosen and bone window created
should allow complete visualization of the entire extent of the lesion. Minimally invasive
techniquesthatproviderestrictedaccesstothelesionshouldbeusedwithcautionduetothe
elevated risk of recurrence. It may be necessary to reconstruct articular surfaces due to
subchondralerosion.Anyjointinvasionisusuallysecondarytopreviousinstrumentation.
Recurrenceiscommon,andrecurrentlesionsshouldbetreatedwithrepeatcurettage.Ifa
recurrent lesion is located in a readily reconstructable location, marginal resection with
structuralallograftorautograftreconstructionispreferable.Recurrenceandseveredestruction
ofboneintegrityinthe footandanklemaynecessitateanklearthrodesisorenblocresection
with associated functional loss. Chondroblastoma can behave aggressively and invade soft
tissue,andmetastasizetothelungs.Patientswithrecurrentlesionsshouldhavefollow-upCT
scansofthechesttodetectpulmonarynodules.Benignpulmonarymetastaseshavebeentreated
withobservationaswellasexcisionviathoracoscopy.
PreferredMarginforThisTumor
Intralesional.
OutcomesofTreatmentandPrognosis
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Functionaloutcomes of surgical treatment ofchondroblastoma are generallygood,provided
thetumorisnotdiscoveredverylateandthatthetumordoesnotrecur.Forlesionslocatedin
theproximalpartofthefemurandinthefootandankle,recurrenceiscommon,andoutcomes
aregenerallyworsethaninotherlocationsintheskeleton.Theriskofrecurrenceappearstobe
highestforlesions located only inthe epiphysis, as opposed to lesions inthe apophysis or
those that extend into the metaphysis or diaphysis. Recurrence is not definitely related to
patientage,sex,ordemographicdata,butitisgenerallyheldthatpatientswithopenphysesare
atincreasedrisk.
UnicameralBoneCyst
IntroductionandDefinition
UBCs,alsoknownassimplebonecysts,arelesionsthatconsistofafluid-filledcavitylined
byathin membrane.Theyarefoundinthemetaphysisoflongbones,withthe mostcommon
sitebeingtheproximalhumerus,followedbytheproximalfemur.“Active”cystsarelocated
neartheepiphysis(suchasinthetoptwoimages),andastheymovefartheraway(suchasin
thethirdimage)asthechildgrowstheybecomeinactive.Thelesionmaybefoundinunusual
sitessuchasthecalcaneusandpelvisinpatientsmorethan17yearsold.TheetiologyofUBCs
is unknown. Several etiologies have beenproposed, including expansion of synovial tissue
trapped inthe boneduringdevelopment, local failure of ossification, or obstructionof the
venousoutflowofthebone.Itispossiblethelesionisareactiontotrauma.Themostpopular
theoryis that local venous obstructioncauses anincrease inpressure thatleads to reactive
boneresorption.ThecystfluidcontainsprostaglandinandinterleukinIβ,whichindependently
cancauseboneresorption.
IncidenceandDemographics
UBCsarefoundmostcommonlyinchildrenbetweentheagesof5and20years,andtheratio
ofmalestofemalesis2:1.
SymptomsandPresentation
Most UBCs are asymptomatic and only present when a pathologic fracture occurs. These
lesionsusuallyhealwhenthepatientisskeletallymature,butafewpersistintoadulthood.The
lesionsgrow inproportiontothe growthofthe bonethey are in.Oncetheboneis finished
growing,theUBCshouldalsostopgrowing.Inthefoot,UBCoccursalmostexclusivelyinthe
calcaneus, andpresents in teenagers or young adults as an incidental finding or with mild
achingpainduringsportsorrunning.Thelocationandappearanceischaracteristicandbiopsy
maynotbeneededtoconfirmthediagnosis.
X-rayAppearanceandAdvancedImagingFindings
The plain film is usually enough to make a diagnosis of an UBC, once the observer is
thoroughlyfamiliarwith theappearanceofthislesion.The lesionappearsasawell-defined
osteolytic area witha thin sclerotic margin.It fills and perhaps slightly expands the juxta-
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epiphyseal metaphysis ofthe bone. The lesionis relativelysymmetrical with respecttothe
midlineaxisofthebone.Thelesionisnoteccentricanddoesnotbreakoutthroughthecortex
orformanyextraosseousmass.Thereisnoperiostealreactionvisibleunlesstherehasbeena
previousfracture.Afragmentofcortexthathasfallenintoadependentpositioninsidethecyst
isknownasthe“fallenleaf”or“fallenfragment”sign.
Inthefoot,UBCoccursalmostexclusivelyinthecalcaneus.Thelocationandappearance
ischaracteristicandbiopsymaynotbeneededtoconfirmthediagnosis.Thelocationisvery
specific.Thelesionisinthelateralportionofthecalcaneussubadjacenttothemiddlefacet.
The apex ofthe lesion is toward the forefoot.The margin of the lesion is sharply defined,
sometimes with a sclerotic rim.There is no matrix mineralization,central calcification,or
periostealreaction.Centralcalcificationisafeatureoflipomasofthecalcaneus.
MRIisusefultodifferentiateUBCfromlipomaofbone,whichmayhavenearlyidentical
location and appearance. MRI demonstrates that the UBC is filled with fluid that has low
signalintensityonT1-weightedimagesandhighsignalonT2images.Inlipomaofbone,the
MRIsignalintensitywillbeidenticaltonearbynormalfat.CTscanisnotespeciallyhelpful
unlesstheUBCisinthepelvis.Onbonescan,UBCshavelightperipheraluptakewithacold
center.However,theuseofbonescanstocharacterizeUBCsisnotrecommended.
LaboratoryFindings
Therearenohelpfullaboratorytestsforthistumor.
HistopathologyFindings
Microscopically,theUBChasamembranemadeup ofalayerofflattenedorcuboidalcells
thatresembleendothelium.Thecystfluidresemblessynovialfluid.Ifafracturehasoccurred,
theremaybeahemorrhage,granulation tissue,calcifications,orgiantcells thatmayconfuse
thediagnosis.
TreatmentOptionsforThisTumor
TreatmentofUBCscantakeseveralforms.ThemerepresenceofaUBCinthecalcaneusdoes
notmandatetreatment.Thephysicianshouldbeextremelyconfidentofthediagnosisprior to
selecting treatment. A consultation is recommended if the surgeon sees bone tumors
infrequently. When the lesion presents with a pathologic fracture, closed treatment of the
fracture is the first priority. Sometimes, the trauma and subsequent healing process of a
pathologicfracturecanbeenoughtocauseresolutionoftheUBC.
UBCsarerelativelycommoninthecalcaneus,butfracturesthroughUBCinthecalcaneus
areuncommon.ThemerepresenceofaUBCinthecalcaneusdoesnotmandatetreatmentfor
the cyst or for possible pathologic fracture. Treatment for asymptomatic cases consists of
observationandfollow-upradiographstoinsurethelesionisnotgrowingorchanging.Painful
cystscanbetreatedwithawidevarietyofmoreorlessinvasivetechniques.Thereisalackof
consensusastotheoptimumchoiceoftreatment.Thereissomeevidencetosuggestthatopen
curettagewithallograftingismostlikelytoleadtoclinicalandradiographicresolutionofthe
cyst.
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Publishedtreatment techniquesinclude aspirationand injectionwithmethylprednisolone
acetate (steroids), bone marrow injections, percutaneous grafting with autogenous or
allogenousbonegraftorbonegraftsubstitutes,oracombinationofthese.Surgicaltechniques
include curettage with and without grafting, creating multiple drill holes, and “continuous
decompression” using a percutaneous cannulated screw. All of these techniques have been
shown to be effective for some cysts, although the quality of the supporting evidence is
universallylow.67 Surgical interventions should be reserved for difficult cases. The author
recommends a fluoroscopicallyguidedinjection ofmethylprednisoloneacetate as theinitial
treatmentforsymptomaticlesionsinthecalcaneus.UBCsthatpersistafteratrialofoneortwo
steroid injections should be curetted through a lateral approach and densely packed with
allograftbone chips. There is nogood evidence favoring commercial bone graftsubstitutes
overmorselizedautograftorallograftboneusedtofillUBCs.UBCsinyoungchildrenshould
beapproachedwithgreatcareduetothehighriskofrecurrenceandthepotentialforgrowth
plate damage from surgery. Open curettage and bone graft for UBCs in children carry a
recurrencerateof40%to45%duetodifficultyofcompleteexcisionofthelesion.Damageto
the nearby growth plate may result in growth arrest. Referral to a musculoskeletal tumor
specialistisrecommended.
Varioustechnicalfactorshavebeenproposedthatmayincreasethesuccessrateofsteroid
injections,includingwidespacingoftheneedlestoensurecompletetreatmentofthelesionand
usingradiologic dyetoinsurecompletefilling ofthelesion.Thesetechniquesmaydecrease
theneedformultipleinjections.ArecentCochranereview68concludedthatthequalityofthe
datawasinsufficienttodemonstratethatinjectionsofmethylprednisoloneweremore orless
effectivethaninjectionsofbonemarrow.Thebiologicmodeofactionoftheinjectionsremains
unknown.
PreferredMarginforThisTumor
Intralesional.
AneurysmalBoneCyst
IntroductionandDefinition
This lesionis nota true neoplasm, butrather is thought tobeareactive lesionthatmaybe
causedbyalocalarteriovenousmalformationorvascularinjury.Onetheoryoftheetiologyof
primaryABCsisthattheselesionsaresecondarytoincreasedvenouspressurethatleadsto
hemorrhage and osteolysis. This osteolysis can in turn promote more hemorrhage causing
amplificationofthecyst.Anothertheoryisthattheselesionsdonotarisedenovobut rather
develop secondarilywithin another primarytumor suchas osteoblastoma, and subsequently
enlargeanddestroy allormostoftheprimarytumor. Thetrue causeisunknown.Thereisa
definiterelationshiptolocaltraumainsomecases,andothercasesareassociatedwithanother
tumorsuch as osteoblastoma, chondroblastoma, or fibrous dysplasia. A proportionofthese
lesionsarisedenovowithoutanydefinitetraumaticorneoplasticcause.
AsolidvariantofABChasbeendescribed.Thisvariantconsistsofanonaneurysmaltumor
withidenticalhistologicfindings,whichaffectstheaxialskeletonandtheshorttubularbones
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ofthe hands andfeet. This variant was described bySanerkin et al.69 The solid variantis
associatedwithperilesionaledemaandcyclooxygenase2expressioninthelesionalgiantcells
andspindlecells.
IncidenceandDemographics
ABCisfoundmostcommonlyduringtheseconddecade,andtheratiooffemalestomalesis
2:1.ABCscanbefoundinanyboneinthebody.Approximately6%ofABCsoccurinthefeet.
Themostcommonlocationisthemetaphysisofthelowerextremitylongbones,moresothan
the upper extremity. The vertebral bodies or arches of the spine also may be involved.
Approximatelyone-halfoflesionsinflatbonesoccurinthepelvis.Inthefootandankle,the
metatarsalsarethemostcommonlyaffectedbones.Somepatientshaveahistoryoftraumato
theareaofthelesion.Patientscomplainofpainandaslow-growingmass.Theauthorshave
seenthesolidvariantofABCintheshorttubularbonesoftheforefootandinthetarsalbones
ofthemidfoot.
SymptomsandPresentation
Symptomsaregraduallyincreasing pain,amass, or apathologic fracturethroughthe lesion.
Rapidincreaseislesionsizehasbeenreportedinafewcases.
X-rayAppearanceandAdvancedImagingFindings
Lesionsarelocatedonthesurfaceoftheboneaswellasinthemetaphysisorepiphysis.Plain
radiographs show an expansile lesion with internal septae or longitudinal striations. The
expansile nature ofthislesionmay beverystriking,and thebonemaybemany timeslarger
thannormal.Eveninhighlyexpandedlesions,thereisathineggshelllayerofreactiveboneon
thesurfaceofthelesion.Thislayermaybepoorlymineralizedinactivelesionsthatarestill
growingandbecomemoreapparentasthelesionmatures.Theradiographicappearancemay
bestrikinglyaggressiveintheearlyphaseofgrowth,butafterafewweeksthemarginofthe
lesionbecomes better defined and the appearance is less worrisome. The highly expansile
lesionperched at the endofthebone hasbeendescribed with the catchphrase “finger in a
balloon.” Most patients in the United States will receive treatment well before the tumor
reachesthisstage,sothecatchphrasemaybeofhistoricalvalueonly.
MRI of aneurysmal lesions may show fluid–fluid levels within the lesion, which may
demonstratemultipleseparateloculationsoronelargeloculatedcavity,andthesecanbehighly
suggestiveofthediagnosis,butarenotdiagnostic.ABCappearsonbothT1andT2MRI,with
alowsignalrimencirclingthecysticlesion.CTandbonescanarenothelpfulindiagnosis,but
mayhelpdefinethelesionorruleoutmultiplelesions.CTscancanalsohelpdelineatelesions
in the pelvis or spine where plain film imaging may be inadequate. A careful search for
radiologic signs of the precursor lesion, if any, is recommended. Some of these precursor
lesionsmayhaveaflocculentchondroidmatrixthatmaybeacluetotheirpathogenesis.
LaboratoryFindings
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Norelevantfindings.
DifferentialDiagnosis
Giantcelltumor,UBC,telangiectaticosteosarcoma.
PreferredBiopsyTechniqueforThisTumor
Incisional/combinedwithcurettageifcertaintyofdiagnosisishigh.
HistopathologyFindings
Ongrossexamination,anABCislikeablood-filledspongewithathinperiostealmembrane.
Soft, fibrouswallsseparatespacesfilledwithfriable blood clot.Microscopically,theABC
hascysticspacesfilledwithblood.Thefibrousseptaehaveimmaturewovenbonetrabeculae
aswellasmacrophagesfilledwithhemosiderin,fibroblasts,capillaries,andgiantcells.The
treatmentapproachwill varydepending onthe location andaggressiveness ofthelesion.A
slow-growing, indolent ABC has been observed to regress spontaneously. Selective
embolectomy of nutrient vessels and percutaneous injection of a fibrosing agent are newer
treatmentmodalities. Percutaneousinjectionofmethylmethacrylatewas usedsuccessfullyby
HerveDeramondforanaggressiveABClesioninthesecondcervicalvertebra.
TreatmentOptionsforThisTumor
Treatmentformostlesionscanbeaccomplishedbycurettageandapplicationofahigh-speed
burrtoremoveanadditional2mmofbone.Recurrenceiscommon,approximately20%.The
cystcanbepackedwithbonechipsorPMMAcement.Bonefragilitymustbeaddressedwith
plates, screws, or rods as indicated. During surgical treatment, these lesions may bleed
profuselyuntilremoval iscomplete.Where appropriate,the lesionsmaybe resectedwith a
marginalorwidemargin,suchasinthefibula.Largelesionsinthepelvisorlongbonesmay
require other treatments, such as embolization. Percutaneous transvascular treatments have
beenusedwithgoodresults,andareespeciallyusefulindifficulttoaccesslesionsofthespine
andskullbase.
Local recurrence rates vary widely, with one recent report having 4 recurrences in 40
patients.70Recurrence rates may be ashigh as 20%. Recurrencewas statisticallyrelated to
young age and open growth plates, and may be less likely following wide excision than
following intralesional treatment by curettage. If a recurrence is detected, a thorough
examination of the original radiographs and pathology specimens should be performed to
insure that the primary lesion, if any, is discovered, because this may radically alter the
treatmentplan.Once the precise diagnosis isknown, local recurrencesmayberetreatedby
appropriatemethods.
PreferredMarginforThisTumor
Intralesional.
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LipomaofBone
IntroductionandDefinition
Thisisararebenignbonetumor.Ifpresentinadults,oftenasanincidentalfinding,itisrarely
symptomatic.Themostcommonsiteisthecalcaneus,followedbythefemur.Thislesionhas
alsobeenfoundinmultiplebones,includingthetibia,fibulaulna,andskull.
IncidenceandDemographics
The true incidenceis unknown.Itis thought torepresent0.1%ofbone tumors, but because
thesetumorsdonotcreatesymptoms,mostmaybemissed.Themeanageatpresentationis43
years;malesandfemalesareequallyaffected.
SymptomsandPresentation
Mostofthese tumorsarenotsymptomaticandare discovered as anincidentallesion.Some
patientsmaypresentwithpain,andpathologicfracturecanoccur.
X-rayAppearanceandAdvancedImagingFindings
Lipoma ofbone andUBCinthecalcaneushave verysimilar radiologicappearance.On Xrays, lipoma of bone is located within Ward triangle, and is well defined with a latent,
nonaggressiveappearance,a narrow zone oftransition,apartialsclerotic rim, anda central
calcificdensity.Notalllipomasofbonehavecalcifications.Whenpresent,thecalcificationis
amorphous and without detectable patterns such as rings and arcs or popcorn (chondroid
pattern) or ground glass (fibrousdysplasia pattern).The calcificationis typicallyrelatively
dense,limited,andcentral. UBCsdonotcontaincalcificationsofanytype.Lipomaofbone
typicallyforms a single rounded or roughlyovoid lyticlesion,ratherthanaloculated“soap
bubble”appearancesuchasmightbeseeninABCs,ornonossifyingfibroma.Mildexpansion
ofthebonemaybepresent.Ascleroticrimispresentinthree-quartersofthesetumors.Inthe
calcaneus,allthesefeaturesaresharedtosomedegreebyUBC.Bothoccupythesameregion
of the calcaneus. Lipoma of bone is distinguished principallyby the presence of a central
calcificdensityandbyMRI.
ThetumorhasalowCTattenuationcoefficientconsistentwithfat,withhighattenuationin
areasofcalcification,whenpresent.OnMRI,thetumorhassignalintensityidenticaltothatof
nearbynormalfatonallsequences.Someintraosseouslipomasundergocysticchange,which
isbestseenonMRI.Calcificationsappearasareasoflowsignalintensity.
LaboratoryFindings
Nolaboratoryfindingsareusefulindiagnosis.
DifferentialDiagnosis
UBC,nonossifyingfibroma,ABC,chondrosarcoma,fibrousdysplasia.
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