Rev. bras. ortop. vol.52 número4

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SOCIEDADE BRASILEIRA DE ORTOPEDIA E TRAUMATOLOGIA

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Case

report

Malignant

Triton

tumor:

a

rare

cause

of

sciatic

pain

and

foot

drop

夽

Maribel

R. Gomes

a,∗

,

Alexandre

M.P.

Sousa

b

,

Roberto

J.A.

Couto

a

,

Marco

M.B.

Oliveira

a

,

João

L.M.

Moura

a

_,

_Carlos

_A.

_Vilela

a

a_Hospital_da_Senhora_da_Oliveira,_Servic¸o_de_Ortopedia_e_{Traumatologia,}_Guimarães,_Portugal

b_Instituto_Português_de_Oncologia,_Servic¸o_de_Cirurgia_Geral,_Porto,_Portugal

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Articlehistory: Received13June2016 Accepted21July2016 Availableonline10June2017

Keywords: Tritontumor Nervesheathtumors Sciaticnerve

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b

s

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r

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c

t

Malignantperipheralnervesheathtumors(MPNST)areveryrareandarefrequently local-izedinthebuttocks,thigh,arm,orparaspinalregion;onevariantisthemalignantTriton tumor,withrhabdomyosarcomatousdifferentiation.Theauthorspresentachallenging dif-ferentialdiagnosisofasciaticpainandfootdropinawomanwithhistoryoflumbardisk herniation,whichwasfoundtobecausedbyaTritontumorofthesciaticnerve.She under-wentsurgicalexcision,followedbyradiationandchemotherapy.MalignantTritontumor caseshaverarelybeendescribedandreportedintheliterature.Therecommendedtreatment isradicalexcisionfollowedbyhigh-doseradiotherapyandchemotherapy.Theprognosis, althoughpoor,dependsonthelocation,grade,andcompletenessofsurgicalmargins.

Tumor

de

Triton

maligno:

uma

causa

rara

de

dor

ciática

e

pé

pendente

Palavras-chave: TumordeTriton

Neoplasiasdabainhaneural Nervociático

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Ostumoresmalignosdabainhadosnervosperiféricos(TMBNP)sãomuitorarose localizam-semaisfrequentementenaregiãonadegueira,paraespinal,coxaoubrac¸o;umavarianteé otumordeTritonmaligno,comumadiferenciac¸ãorabdomiosarcomatosa.Apresentamos umdiagnósticodiferencialdesafiantededorciáticaepépendenteemumapacientecom antecedentesdehérniadiscallombar,quesedescobriuqueeracausadaporumtumorde Tritondonervociático.Apacientefoisubmetidaaexcisãocirúrgica,seguidaderadioe

夽

StudyconductedattheHospitaldaSenhoradaOliveira,Servic¸odeOrtopediaeTraumatologia,Guimarães,Portugal. ∗ _{Corresponding}_author.

E-mail:maribelgomes@hospitaldeguimaraes.min-saude.pt(M.R.Gomes).

http://dx.doi.org/10.1016/j.rboe.2017.06.001

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quimioterapia.PoucoscasosdetumoresdeTritonmalignosforamdescritoserelatadosna literatura.Otratamentorecomendadoéaexcisãoradical,seguidaderadioterapiaemalta doseequimioterapia.Oprognóstico,emboramau,dependedalocalizac¸ão,dograuedas margenscirúrgicasdaexérese.

Introduction

Malignanttumorsthatoriginateordifferentiatefromthe var-iousnervesheathlineagesarecollectivelytermedmalignant peripheralnerve sheath tumors(MPNST); they represent a smallpercentageofsofttissuesarcomas,andmaybesporadic orassociatedwithneurofibromatosistype1.1,2

Theyareoftenlocatedinthebuttocks,thighs,arms,orthe paraspinalregion.Mostarehigh-gradesarcomas,whichoften metastasizetothelungsorbone;avariantofthisraretypeis themalignanttritontumor,whichhas rhabdomyosarcoma-tousdifferentiation.1,3

Case

report

Thisstudyreportsthecaseofa45-year-oldfemalepatientwho hadahistoryoflowbackpainandsciaticpainwithprogressive aggravationinthelastsixmonths.AxialCTscanindicatedleft L5-S1diskherniation(Fig.1).Herphysicianreferredhertoan OrthopedicSurgeryspecialistandwaswhileawaitingforthe visitshegotintramuscularnon-steroidalanti-inflammatory drugs(NSAIDs)prescriptions.

However,intheprevioustwoweeks,thepatientdeveloped apainfulswellingintheleftbuttockthatshebelievedtobe relatedto the NSAIDsinjections, attendingthe Orthopedic EmergencyRoom.

Physicalexaminationindicatedahardswellingintheleft buttock,hypoesthesiaoftheleftlegwithnospecificterritory, apositiveLasèguesign,footdropgait,andabsenceofAchilles reflex.

Anultrasoundexaminationofthebuttockwasperformed, whichindicatedavascularizedmassintheleftglutealregion. Magnetic resonance imaging (MRI) confirmed a heteroge-neouslesionof10.5×4.5cm,deepintheglutealmuscles,that

entered the pelviccavity throughthe greater sciatic notch (Figs.2and3).

Thepatient underwent tru-cut biopsy,which revealed a malignanttritontumor;onemonthlater,sheunderwenten blocresectionofthetumorandsciaticnerveroots.Twomonths aftersurgery,adjuvantradiotherapy(RT)andchemotherapy (doxorubicin)wereinitiated.

Histopathologyindicatedthatthesurgicalresectionwas complete; together with the imagingdata, the lesion was stagedasagrade-IIIpT2bN0M0tumor.

Four months after surgery, hypoesthesia and drop foot persisted; electromyography confirmed neurotmesis of the sciatic nerve. She was referred for physical medicine and

Fig.1–SagittalsectionofaT2-weightedlumbarspineMRI disclosingofL5-S1diskherniation.

rehabilitation,followedthephysiotherapyplan,andwalked withananti-equinusorthosis.

Ateightmonthspostoperatively,shepresented dysesthe-siaandcomplainedofpainatthelevelofthepelvis,irradiating tothe left lower limband refractorytoanalgesia.Shealso presentedfever,dyspnea,constipation,andurinaryretention. Thepatientwasadmitted;anewlumbarspineandhipMRI wererequested,aswellasathoracicCT.

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Fig.2–CoronalsectionofaT2-weightedpelvicMRIdisclosingthelesionintheleftglutealregion.

Fig.3–AxialsectionofaT2-weightedpelvicMRIidentifyingthelesionintheleftglutealregion.

Atninemonthspost-operatively,shediedofprogressive respiratoryfailureandamine-refractoryshock.

Discussion

Traditionally,thediagnosisofMPNSThasbeendifficultamong softtissuetumorsduetothelackofstandardizeddiagnostic andhistologicalcriteria.Todate,therearenospecific biomark-ersthatcanhelpestablishthediagnosis.Thedivergenceinthe

diagnosticcriteriahasalsocontributedtothevariabilityofthe incidenceofsuchlesiondescribedintheliterature.3

MPNSToccurmostlybetweentheagesof20and50, affect-ingbothgendersequally.Inpatientswithneurofibromatosis type1,thesetumorstendtooccurinmales,atanearlierage, andtohavelargerdimensions.1–3

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Fig.4–AxialsectionofaT2-weightedpelvicMRIinthepostoperativeperiod.

Fig.5–AxialcutofthoracicCTinthepostoperativeperiod.

swelling. The association of MPNST with the main nerve trunksexplainsitsgreaterincidenceintheproximalregions ofthelimbsandthetrunk(sciaticnerve,brachialplexus,and sacralplexus).3

Histologically,thesetumorsarecomposedof hyperchro-matic fusiform cells arranged in a fasciculated pattern. High-grade tumors usually contain areas of necrosis and increasedmitoticactivity.2,3

Thecapacity ofMPNSTtoundergo mesenchymal differ-entiation is well known. The malignant triton tumor is a rarevariantwithrhabdomyosarcomatousdifferentiation,first describedin1938byMassonandMartin.Itconsistsofastroma

typical ofMPNST, with additionalrhabdomyoblasts, which usuallyarisesphericallyandwitheosinophiliccytoplasm.2,3

Fewcasesofmalignanttritontumorshavebeendescribed intheliterature.Asthesearelesionswithahighprobability oflocalanddistantrecurrence,therecommendedtreatment isradical excisionfollowed byhigh-dose radiation therapy, although more recent studies suggest that chemotherapy mayeradicatemicrometastasesandextendsurvival.1,3

Dur-ingfollow-up,CTandpositronemissiontomographyarethe examsofchoiceintheevaluationofrelapses.2,3_The

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Thepresentcasehassomeparticularitiesthatmayhave causedadelayindiagnosisandmadeitevenmore challeng-ing.ThehistoryoflowbackpainwithadocumentedleftL5-S1 diskherniationcouldperfectlyexplainthesymptoms,leading theattendingphysiciantoreferthepatienttoanorthopedic surgeon.

Thedistinctivefeatureofthisclinicalcasewastheswelling intheleftbuttock,whichmayhaveraisedtheclinical suspi-cionofanothercauseforclinicalpresentation.

Enblocresectionofthetumoraswellasthesciaticnerve and its rootscontributed to postoperative motor and sen-sorydeficits,butwasanecessaryprocedure,sincethetumor invadedthenerve.Completesurgicalresectionandabsenceof nodularordistantmetastaseswouldrepresentgood prognos-ticfactors.However,thistypeoftumorhasagenerallypoor prognosis,whichwasconfirmedinthiscase.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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1.Fanburg-SmithJC.Nervesheathandneuroectodermaltumors. In:FolpeAL,InwardsCY,editors.Boneandsofttissue pathology.Philadelphia:Saunders;2010,193-23.8.

2.GoldblumJR,WeissSW,FolpeAL.Malignantperipheralnerve sheathtumors.In:EnzingerandWeiss’ssofttissuetumors.6th ed.Philadelphia:Elsevier;2014.p.855–79.