SkiptomaincontentThankyouforvisitingnature.com.YouareusingabrowserversionwithlimitedsupportforCSS.Toobtainthebestexperience,werecommendyouuseamoreuptodatebrowser(orturnoffcompatibilitymodeinInternetExplorer).Inthemeantime,toensurecontinuedsupport,wearedisplayingthesitewithoutstylesandJavaScript.AdvertisementnaturemodernpathologyoriginalarticlearticlePleomorphicRhabdomyosarcomainAdults:AClinicopathologicStudyof38CaseswithEmphasisonMorphologicVariantsandRecentSkeletalMuscle-SpecificMarkersDownloadPDFAbstractPleomorphicrhabdomyosarcoma(PRMS)isarareandcontroversialtumorofskeletalmusclephenotype.DiagnosticcriteriaforPRMSbycombinedhistologyandcurrentlyavailableimmunohistochemistryhavenotbeenclearlydefined.Wereport38pleomorphicrhabdomyosarcomasinadults,exploremorphologicvariants,anddiscussourexperiencewithbothspecificandnonspecificskeletalmusclemarkersinthesetumors.Clinicaldata,morphology,andimmunohistochemistrywerereviewed.Electronmicroscopywasperformed.Of38cases,therewere28malesand10females.Patientagesrangedfrom21to81years(median=54y;mean=51y).Tumorswerelocatedinthelowerextremity(n=18),abdomen/retroperitoneum(n=6),chest/abdominalwall(n=5),spermaticcord/testes(n=4),upperextremity(n=3),andoneeachinthemouthandorbit.Tumorsizesrangedfrom1.5to15.0cm(mean=7.3cm;median=6.8cm).Thecasesweredividedintothreevariants,eachwithlarge,atypical,pleomorphicpolygonalrhabdomyoblasts(PRMB)withabundanteosinophiliccytoplasminvaryingnumbersanddifferentmorphologicbackgroundsofroundorspindledrhabdomyoblasts(RMB).1.ClassicPRMS:PredominantlyatypicalPRMBinsheets(n=8).2.RoundcellPRMS:ClustersofPRMBthroughoutthetumorwithabackgroundofslightlyatypical,medium-sized,round,blueRMB(n=13).3.SpindlecellPRMS:ScatteredPRMBinapredominanceofatypicalspindledRMBarrangedinastoriformgrowthpattern(n=17).Immunohistochemistryrevealedthefollowing:myoglobin(37/38),MyoD1(19/36),skeletalmusclemyogenin(myf4;19/34),fastskeletalmusclemyosin(4/5),desmin(36/38),muscle-specificactin(MSA;25/35),smoothmuscleactin(SMA;15/33),andmuscl