MORPHOLOGYClear cell cancers (themostcommonformofrenalcarcinomas)usuallyaresolitaryandlargewhensymptomatic(sphericalmasses3to15cmindiameter),buthigh-resolutionradiographictechniquesforinvestigationofunrelatedproblemssometimesdetectsmallerlesionsincidentally.Theymayariseanywhereinthecortex.Thecutsurfaceofclearcellrenalcellcarcinomasisyellow to orange to gray-white, with prominent areas of cystic softening or of hemorrhage, eitherfreshorold(
Fig.14.24 ).Themarginsofthetumorarewelldefined.However,attimessmallprocessesprojectintothesurroundingparenchymaandsmallsatellitenodulesarefound,providingclearevidenceoftheaggressivenessoftheselesions.Asthetumorenlarges,itmayfungatethroughthewallsofthecollectingsystem,extendingthroughthecalycesandpelvisasfarastheureter.Evenmorefrequently,thetumor invades the renal vein andgrowsasasolidcolumnwithinthisvessel,sometimesextendinginserpentinefashionasfarastheinferiorvenacavaandevenintotherightsideoftheheart.Occasionally,directinvasionintotheperinephricfatandadrenalglandmaybeseen.
Dependingontheamountsoflipidandglycogenpresent,the neoplastic cells of clear cell renal cell carcinoma may appear almost vacuolated or may be solid. Theclassicvacuolated(lipid-laden)cellsorclearcellsaredemarcatedonlybytheircellmembranes.Thenucleiareusuallysmallandround(
Fig.14.25 ).Attheotherextremearegranularcells,resemblingthetubularepithelium,whichhavesmall,round,regularnucleienclosedwithingranularpinkcytoplasm.Someneoplasmsarehighlyanaplastic,withnumerousmitoticfiguresandmarkedlyenlarged,hyperchromatic,pleomorphicnuclei.Betweentheextremesofclearcellsandsolid,granularcells,allintergradationsmaybefound.Thecellulararrangement,too,varieswidely.The http://ebooksmedicine.net
Fig. 14.24 Renalcellcarcinoma:Representativecross-sectionshowingyellowish,sphericalneoplasminonepoleofthekidney.Notethetumorinthedilated,thrombosedrenalvein.
cellsmayformabortivetubulesormayclusterincordsordisorganizedmasses.Thestromaisusuallyscantbuthighlyvascularized.
Papillary renal cell carcinomas exhibitvariousdegreesofpapillaformationwithfibrovascularcores.Theytendtobebilateralandmultiple.Theyalsomayshowgrossevidenceofnecrosis,hemorrhage,andcysticdegeneration,buttheyarelessvibrantlyorange-yellowbecauseoftheirlowerlipidcontent.Thecellsmayhaveaclearor,morecommonly,pinkcytoplasm.Chromophobe-type renal cell carcinoma tendstobegrosslytan-brown.Thecellsusuallyhaveclear,flocculentcytoplasmwithveryprominent,distinctcellmembranes.Thenucleiaresurroundedbyhalosofclearcytoplasm.Ultra-structurally,largenumbersofcharacteristicmacrovesiclesareseen.
Fig. 14.25 Theclearcellpatternofrenalcellcarcinoma.