Markers useful for separating Paget disease from other processes. CK7 is the most useful marker as it is not expressed by the surrounding epidermal cells.SurgicalPathologyCriteriahttp://surgpathcriteria.stanford.edu/usebrowserbackbuttontoreturnExtramammaryPagetDiseaseDefinitionIntraepithelialinvolvementoftheskinby(non-squamous)carcinomacellsDiagnosticCriteriaIntraepithelialpopulationoflargeatypicalcells(Pagetcells)distinctfromsurroundingnormalepithelialcellsLargenuclei,prominentnucleoliAbundantpalecytoplasmScatteredindividuallyandinclustersMayformsmallaciniLackfeaturesofsquamousdifferentiationNovisibleintercellularbridgesNotransitiontosurroundingsquamouscellsMostcasesmucinpositiveMayformsignetringsUnderlyingchronicinflammationcommonEpidermalhyperplasiaandhyperkeratosisandparakeratosisfrequentlypresentPresentinhalfofcases>90%ofanalcasesThreepatternsdescribedSquamoushyperplasiaNOSMayresultinpseudoepitheliomatoushyperplasiaFibroepithelioma-likeAnastomosingnetworkofreteridgesEspeciallyfrequentinperianalcasesPapillomatousHPVnegativePagetcellsmaybeshrunkenandpyknoticExtramammaryPagetdiseasecanbeseparatedintoprimaryandsecondarytypesPrimarytypenotassociatedwithunderlyingdeepcarcinomaPositiveforGCDFP15andnegativeforCK20(seeSupplementalStudiesandDifferentialDiagnosisatleftsidebar)Invasionisuncommon,butcanoccurSecondarytypeisassociatedwithanunderlyinginternalcarcinomaNegativeforGCDFP15andfrequentlyCK20positivePhenotypemaydependuponnatureofunderlyingcarcinomaMostcommonunderlyingcarcinomasRectaladenocarcinomaUrothelial(transitionalcell)carcinomaMostcommonlocationsVulvaAnal/perianalScrotumandpenisInguinalTeriALongacreMDRobertVRouseMDDepartmentofPathologyStanfordUniversitySchoolofMedicineStanfordCA94305-5342Originalposting/updates:10/7/10SupplementalstudiesImmunohistologyMarkersusefulforseparatingPagetdiseasefromotherprocessesCK7isthemostusefulmarkerasitisnotexpressedbythesurroundingepidermalcellsNormalTokercellsandMerkelcellsarepositiveforCK7andmustbedistinguishedmorphologicallyC