* Corresponding author: Jin-Suk Kim, Department of Nuclear Medicine, Konyang University Hospital, 685 Gasuwon-dong, Seo-gu, Daejeon 302-718, South Korea. Tel: 82-42-600-9474; Fax: 82-42-600-9499; E-mail: airrice54@hanmail.net © 2014 mums.ac.ir All rights reserved. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.  

   

InflammatoryPseudotumorintheEpiduralSpaceofLumbosacralSpineon18F‐FDGPET/CTJin‐SukKim1,ShinYoungPark21 DepartmentofNuclearMedicine,KonyangUniversityHospital,Daejeon,SouthKorea2 DepartmentofPathology,KonyangUniversityHospital,Daejeon,SouthKorea

ARTICLEINFO ABSTRACT

Articletype:Casereport

Aninflammatorypseudotumor(IPT)isararebenignlesion,characterizedbynon‐neoplastic proliferation of inflammatory cells and presence of interminglingcollagenfibers.IPTcommonlyoccursinthelungsandorbita,whileanintraspinalIPT is extremelyrare. IPTcanmimicbothclinicallyandradiologicallymalignantprocesses, and making a definitive preoperative diagnosis is often difficult.Recently, 18‐fluorine fluorodeoxyglucose (18F‐FDG) has been reported toaccumulate in IPT in the lung, spleen, liver, pancreas, colon, orbit,mediastinum,andmesentery.However, to thebestofourknowledge,accumulationof18F‐FDGhasnotbeenreportedinlumbosacralintraspinalIPT.Herein,wereportacaseofIPTintheepiduralspaceofthelumbarspine,usingtheimagingfindingsof18F‐FDGpositron emission tomography‐computed tomography (PET/CT) and contrast‐enhancedmagnetic resonance imaging (MRI). This is the first case of IPT in theepidural space, depicted by 18F‐FDG PET/CT, which revealed a homogeneous,intense18F‐FDGuptake.

Articlehistory:Received:10Jun2014Revised:24Jun2014Accepted:1Jul2014

Keywords:InflammatorypseudotumorEpiduralspaceLumbosacralspine18F‐FDGPET/CT

►Pleasecitethispaperas:KimJS,ParkSY.InflammatoryPseudotumorintheEpiduralSpaceofLumbosacralSpineon18F‐FDGPET/CT.AsiaOceaniaJNuclMedBiol.2014;2(2):138‐142.

IntroductionInflammatorypseudotumor(IPT)isabenign

tumor‐like lesion of unknown etiology, whichhas been identified in very small numbers atvarious locations throughout the body. It ismostly found in lungs with extrapulmonaryoccurrences at sites including the orbit, nasalsinuses, liver, spleen, pancreas, intestine,kidney, urinary bladder, testis, heart, andlymphaticsystem(1).

Todate, theappearanceof IPT in thespinalcanal has been extremely rare. This conditionhas been successfully treated by surgicalremoval,steroidtherapy,andradiationtherapyto the residual mass (2). It is difficult todifferentiate this pseudotumor from trueneoplasm,bothclinicallyandradiologically.

Herein,wepresent the firstcaseofepiduralIPT in the lumbar spine, using 18‐fluorinefluorodeoxyglucose(18F‐FDG)positronemission

tomography‐computedtomography(PET/CT).

CaseReportA 43‐year‐old man was admitted to the

hospital complaining of lower back pain withradiation to the right lower extremity. His painhad steadily worsened and he had beenexperiencing weakness of the right lowerextremityforoneandahalfmonths;inaddition,hewas suffering frommildbladderdysfunction.There was no previous history of trauma oranticoagulationtherapy.Hemoglobinlevel,whitebloodcellcount,erythrocytesedimentationrate,C‐reactive protein level, and the results of liverfunction test were all normal; also, the findingsonX‐raysofchestandthoracolumbarspinewerenormal.

The lumbar spine CT scan showed a homo‐geneous mass‐like lesion with enhancement

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Figure 1.A subtly enhancing mass‐like lesion in the rightepidural space without bony destruction, observed on thelumbarspineCTscanin the right epidural space (Figure 1). Magneticresonance imaging (MRI) demonstrated anepiduralmass fromL4‐5 toS2, compressing thethecal sac, and extending to the right epiduralspace along the nerve root. It involvedhomogeneous isointensity on the T1‐weightedimage, heterogeneous iso‐ and hypointensity ontheT2‐weightedimage,andstrongenhancement(Figure 2). MRI also showed abnormal signalintensityintheadjacentbackmuscle.

There was no evidence of adjacent bonedestruction or bony sclerosis on CT or MRIimages.Thedifferentialdiagnosesincludedspinalepiduralmalignancies,suchasspinal lymphoma,metastatic tumor, or epidural abscess. Thepatient underwent 18F‐FDG PET/CT(Gemini TF,PhilipsHealthcare,OH,USA) forthedetectionofprimary cancer and metastatic disease. Theimaging showed intense uptake of FDG withmaximal standardized uptake value (SUVmax) of6.7 in the right epidural space (Figure3).Therewas no abnormal FDG uptake in other organsexcept the spinal canal. This finding suggestedthat a primary tumor rather than metastasisoriginatedinthespinalcanal.

We performed an L5‐S1 hemilaminectomyandmicroscopic subtotal resection of themass,which was located in the epidural space insidethe ligamentum flavum. The mass was highlyhypervascular and firmly attached to the dura,the ligamentum flavum, and the bone.Histologically, the tumor consisted of infiltratedinflammatorycellsincludinglymphoplasmacells,neutrophils, and eosinophils in a background ofstroma,composedofmyofibroblastsandcollagenbundles(Figure4).

Figure2.(A)MRIrevealsanexpansilerightepiduralmassfromL4‐5toS2,showinghomogeneousisointensityonthesagittalT1‐weightedimage,(B)heterogeneousiso‐andhypointensityonthesagittalT2‐weightedimage,(C)sagittalgadolinium‐enhancedT1‐weightedimage,and(D)axialimage;astrongenhancinglesionwithcordcompressionandabnormalsignalintensitywasdetectedintheadjacentbackmuscle

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140 Asia Oceania J Nucl Med Biol. 2014; 2(2):138-142.

Figure3.18F‐FDGsagittalmaximumintensityprojection(MIP,A),axialPET(B),axialPET/CT(C),sagittalPET/CT(D),andcoronalPET/CT(E)imagesdemonstratedintenseFDGuptake(SUVmax6.7),correspondingtotherightspinalcanalofthelumbosacralspine;therewasnoabnormalFDGuptakeinotherregionsTable1.PreviousreportsofcaseswithepiduralinflammatorypseudotumorsinthespineSource Age(y)/sex Location Co‐morbidityRobertsetal.,1997(1) 58/F T9‐T11 HypertensionGilliardetal.,2000(6) 45/M C3‐T2 MultifocalfibrosclerosisRobertsetal.,2001(7) 39/F T5‐T6 NoneSeoletal.,2005(8) 44/M T1‐T7 NotreportedSailleretal.,2006(9) 78/M C6‐T3 Giantcellarteritis 73/F T5‐T7 GiantcellarteritisKatoetal.,2012(10) 63/M T5‐T6 PolymyalgiarheumaticaThepresentcase 43/M L4‐S2 None

Figure 4. Microscopically, the epidural mass showedextensive infiltration of lymphocytes, neutrophils, andfibrosis(H&E,×200)

Immunohistochemical staining showed < 2

IgG4‐positiveplasmacellsperhighpowerfield,and the tumor was diagnosed as aninflammatory pseudotumor. After surgery, thepatientstartedsteroidtherapyandhispainandneurologicsymptomssteadilyimproved.

Discussion

IPT,whichissynonymouswithinflammatory

myofibroblastic tumors, is a rare benign tumorwith unknown pathogenesis. Clinical featuresandimagingfindingsofIPTaresimilartothoseof malignant tumors. This tumor consists of abackground proliferation of spindle‐shapedmesenchymal cells, associated with a variableinfiltrationofinflammatorycells.

IPTmost commonly involves the lungs andorbita, but it has been reported to occur innearly every site in the body (3). Although thecentralnervoussystemistherarestsiteaffectedbyIPT,morethan100sporadiccaseshavebeenreportedintheliterature(4,5).IntraspinalIPTsareextremelyrare.Exceptforthepresentcase,we only found seven previous reports ofepidural IPT in the spine, andall of themwerelocatedinthecervicalorthoracicspine(1,6‐10)(Table 1). Furthermore, these cases were notdescribedusingthe18F‐FDGPET/CTfindings.

The current case is the first report of anepidural IPT in the lumbosacral spine, whichshowedahighuptakeofFDG,asdetectedby18F‐FDG PET/CT. The clinical and imagingcharacteristicsofIPTarenon‐specific,sincethelesionhas awide rangeof clinical and imagingpresentations. Hence, the diagnosis of IPT can

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bemadeonly afterother specificdisorders areruledout.Commonly, thedifferentialdiagnosesconsidered in spinal IPT cases include spinallymphoma, metastatic tumor, and multiplemyeloma(8).

Radiologically, IPT appears as a solidintraspinal tumor. On MRI images, IPT usuallyhas a low signal intensity on both T1‐ and T2‐weighted images,whichmayreflectthefibroticnatureof these lesions. Contrast‐enhancedMRImay show a homogeneous or heterogeneouslesion and delayed imaging often showsincreasingenhancementdue to thepresenceoffibrosis(11).

To our knowledge, there have been noreportsonintraspinalIPTwith18F‐FDGPET/CT.However,asinourcase,markedincreaseinFDGuptakehasbeenalreadyreportedasafeatureofIPT (12‐16). It is well established that FDGuptake is not specific to malignant neoplasms,and it may be observed in a variety of tissueswithincreasedglucoseconsumption.

The mechanism of high FDG uptake in IPTmay be related to inflammatory cells in thepseudotumor(16).Asneutrophilswerefoundinthetumorbasedonthehistopathologicalfindingsinthiscase,theirpresencemaycontributetothemechanismofFDGuptakeinIPT.

It is impossible to distinguish malignantneoplasms from inflammatory pseudotumorsbased on imaging findings of MRI and 18F‐FDGPET/CT; therefore, without a biopsy, making adifferential diagnoses is very difficult. However,18F‐FDGand18F‐FDGPET/CThavebeenreportedtobeuseful inevaluating the therapeuticeffectsof steroidor radiation therapieson IPT in caseswithincompletesurgicalresection(17,18).

Surgical excision is usually mandatory inIPT, compressing the spinal cord, due to theemergent need to relieve the mass effect; it isgenerally curative when total excision isperformed. Radiotherapy, systemic steroid, orimmunosuppressive drugs are alsoadministeredforIPTpatients,whichmayleadtoadecreaseinthemassvolume(6,19,20).

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