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Introduction

Malignant peripheral nerve sheath tumour(MPNST)isararesarcomacommonlylocatedindeepsofttissueoftheupperandlowerextremitiesandtrunk(1).Involvementoftheheadandneckisuncommon.Among the sarcomas, it isoneofthe most aggressive malignant tumours, withthe highest local recurrence rate and a markedpropensity for metastatic spread. A definitivediagnosisofMPNSTisobtainedbyhistopathologyand S-100 immunostaining. Most cases ofMPNSTexhibitspindlecellhistomorphology.Theepithelioidvariantordifferentiationisararebutwell-recognized entity comprising of about 5%of MPNST (2,3). Once diagnosis is made, wideexcisionisthemainstayoftreatment.Wereportacaseofanelderlymalewithepithelioidmalignantperipheralnervesheathtumouroftheskullbase,involvingextensivelocalinvasion,andmetastaticdepositsinthenecknodes.

Case Report

Submitted: 5Jul2012Accepted: 2Sept2012

Widely Infiltrating Epithelioid Malignant Peripheral Nerve Sheath Tumour of Skull Base

Srilatha ParamPalli SrinivaS1, Lakshmi rao2, Deepak Ranjan nayak3

1 Department of Pathology, Melaka Manipal Medical College, Manipal campus, Manipal University, Manipal-576104, Karnataka, India

2 Department of Pathology, Kasturba Medical College, Manipal University, Manipal-576104, Karnataka, India

3 Department of ENT Surgery, Kasturba Medical College, Manipal University, Manipal-576104, Karnataka, India

Abstract Theepithelioidvariantofmalignantperipheralnervesheathtumoursisararehistologicalentity,andtheoccurrenceofamalignantperipheralnervesheathtumourintheskullbaseisevenmoreunusual.Wereportacaseofa52-year-oldmanwhopresentedwithreducedhearingintheleftear,giddinessandleft-sidedfacialweaknessofshortduration.Hewasaknownhypertensive.Onexamination,left-sided7thto12thcranialnervepalsieswerenoted.Computedtomography(CT)andbrainmagneticresonanceimaging(MRI)werereportedasanill-definedheterogeneouslyenhancingmassleftskullbasesuggestiveofchondrosarcoma.Lefttympanotomyandbiopsyofthelesionwerecarriedout.Onlightmicroscopyandimmunohistochemicalexaminationofthebiopsy,adiagnosisofepithelioidmalignantperipheralnervesheathtumourwasestablished.Thepatientunderwentleftextendedmodifiedradicalmastoidectomyandselectiveneckdissection.Histopathologicalstudyoftheresectedsurgicalspecimenconfirmedleft-sidedextensivetumourinvolvementofskullbasestructures,aswellasnecknodalmetastases.

Keywords:Nerve sheath neoplasm, malignant schwannoma, skull base

Case Report

A 52-year-oldmale presentedwith reducedhearing of the left ear lasting two months, andgiddiness, voice change and facial weaknessof one week’s duration associated with nasalregurgitation.Thepatientisaknownhypertensiveon treatment. He gave a past history ofcerebrovascularaccidenttwoyearspreviously.Ongeneral examination, no skin lesions suggestiveof neurofibromatosis-1 (NF-1) were noted. Onexaminationof the central nervous system, left-sided7thto12thcranialnervepalsieswerenoted.Computedtomography(CT)andbrainmagneticresonance imaging (MRI) showed an ill-definedmass lesion in the left jugular foramen, causingdestruction of adjacent bones, the left occipitalcondyle, the clivus, the mastoid part of facialcanaland the leftmastoidaircells (Figure1). Itwasreportedassuggestiveofchondrosarcomaoftheskullbase.Lefttympanotomyandbiopsywere

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carried out. Histopathology showed malignanttumour comprising sheets and fascicles ofspindledcellswithmoderatecytoplasm,andovaltospindlynucleiwithfinetocoarsechromatinandsmallinconspicuousnucleoli.Areasofepithelioiddifferentiation with abundant eosinophiliccytoplasm, vesicular nucleus and prominentnucleolus, frequent mitoses and occasionaltumour giant cells were seen (Figure 2 and 3).Tumour cells were focally positive for S-100(Figure4)andnegativeforcytokeratinAE1/AE3andHMB45.Adiagnosisofmalignantperipheralnerve sheath tumourwith epithelioid areaswasrendered. The patient underwent left radicalmastoidectomy and selective neck dissection.Intra-operatively, a fleshy mass was seeninvolving the posterior wall of the middle earextendingintothemesoandhypotympanum,themastoidsegmentofthefacialnerve,perisigmoidsinuscells,themastoidantrumandabuttingtheduraof theposteriorandmiddle fossa.Biopsieswere taken from the above mentioned areas.The left facial nerve, level IIA and IIB cervicallymph nodes and spinal accessory lymph nodeswere resected.Onhistopathology of the tumourbiopsies, a malignant peripheral nerve sheathtumourwithpredominantepithelioidareas,areasof geographic necrosis and haemorrhage were

Figure1:MRIofskullbaseshowingthetumour(markedwitharrow).

Figure 2: High power (40× magnification)microscopic view of the tumourshowingepithelioiddifferentiation.

Figure 3: Low power (20× magnification)microscopic view of the tumourshowing necrosis (marked byarrow).

Figure 4: Immunohistochemistry: Focal S-100positivity.

Case Report |Malignantperipheralnervesheathtumour

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noted. Left level IIB and the spinal accessorylymphnodeswerepositiveformetastaticdeposits.Afinaldiagnosisofwidelyinfiltratingepithelioidmalignant peripheral nerve sheath tumour ofthe skull basewith lymphnodalmetastasiswasestablished. Twoweeksfollowingthesurgery,thepatientdevelopedmassivehaemorrhagicpleuraleffusion.The cytology of the effusion was negative formalignancy.Thepatientremainedintheintensivecare unit for four days and was subsequentlydischargedagainstmedicaladviceduetofinancialconstraints.

Discussion MPNST, also known as malignantschwannomaorneurofibrosarcoma,accountsfor5% to 10%ofall soft tissue sarcomas. Itusuallypresents in adult life between 20 and 50 yearsof age. It arises as de novo, from pre-existingbenign neurofibroma and schwannoma orfollowing irradiation. Ithasa strongassociationwithNF-1(3,4).Inourcase,therewerenovisiblemanifestationsofNF-1. Approximately 80–85% of MPNST arespindle cell tumours with fasciculating patternsthatcontainhistologicalfeaturessimilartothoseof a fibrosarcoma. They are often high grade,demonstrating four or more mitotic figures perhighpowerfieldandareasofgeographicnecrosis.The remaining 15% of MPNST is composed oftumours that exhibit variable differentiation,allowing them to be sub-classified as distinctentities. These include epithelioid, glandular,rhabdomyoblastic(malignanttritontumour)andmelanocyticvariants(1,5).Ourcaserepresentstheepithelioid variantofMPNST,which constitutesabout 5% of MPNST. The biological behaviourand prognosis of this variant is not clear (6).Differential diagnosis of this variant includesmalignantmelanoma,metastatic carcinomaandepithelioidsarcoma.Immunohistochemistryhelpsindiagnosis.MPNSTispositiveforS-100,Leu7,and myelin basic protein. Malignant melanomaispositiveforS-100andHMB45(7).Metastaticcarcinomaispositiveforcytokeratinandepithelialmembrane antigen (EMA). Epithelioid sarcomashowspositivity forcytokeratin,EMA,vimentin,andCD34. MPNST is a very aggressive tumour whichspreads via direct perineural invasion and thehematogenous route. The local recurrence rateis about 54%and the rate of distantmetastasestolungandboneisabout65%(8).Lymphnodal

metastasisoccursinconjunctionwithwidespreaddisease (9). In our case, therewas lymphnodalmetastasis. Treatment is aimed at radicalresection followed by adjuvant radiotherapyand chemotherapy. Since tumours in the headand neck are in proximity to vital structures, acompleteradicalresectionisnotpossible;hence,fractionalexcisioniscommon.Prognosisofheadandnecktumoursarepoorercomparedtothoseof the extremities and the trunk,withfiveyearssurvivalratesfrom15%to35%(3).

Conclusion

In conclusion, MPNST involves a highrate of local invasion, distant spread, and localrecurrence. MPNST of the head and neck hasa poorer prognosis compared to that occurringin the trunk and extremities due to incompleteexcision.

Acknowledgement

Nil.

Conflict of interest

Nil.

Fund(s)

Nil.

Authors’ Contributions

Conception and design, collection and assemblyofdata:PSSDraftingofthearticle:PSS,LRCritical revision of the article for the importantintellectual content and final approval of thearticle:PSS,LR,DRNAdministrative,technicalorlogisticsupport:LRProvisionofstudymaterialsorpatient:DRN

Correspondence

ProfessorDrSrilathaParampalliSrinivasMD(India)DepartmentofPathologyMelaka Manipal Medical College (Manipal campus)Manipal,Karnataka,576104IndiaTel:+0091-08209740965865Fax:+91-8202571905Email:drsrilatha2003@hotmail.com

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