Fig.19.29F ).TheyconsistofsheetsoflargeanaplasticcellsassociatedwithpronouncedlymphocyticinfiltratescomposedpredominantlyofTcells(
Fig.19.29E ).Thepresenceoflymphocytesisassociatedwithafavorableprognosis,atleastinpartduetoabetterresponsetochemotherapycomparedtopoorlydifferentiatedcarcinomaswithoutlymphoidinfiltrates.ThistypeofcarcinomaisseenfrequentlyinwomenwithgermlineBRCA1 mutations,butmostwomenwiththesecarcinomasarenotcarriers.
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Fig.19.29Growthpatternsofinvasivebreastcarcinomas.(A)Mostgrowastubules(“ductal”carcinoma)andstimulateareactivedesmoplasticstromalproliferation.Inmammograms(B),thesecarcinomasappearasdensemasseswithspicularmarginsresultingfrominvasionofadjacentradiolucentbreasttissue.(C)Lobularcarcinomasarecomposedofnoncohesivetumorcellsthatinvadeaslinearcordsofcellsandinducelittlestromalresponse.Accordingly,inmammograms(D)lobularcarcinomasoftenappearasrelativelysubtle,irregularmasses(arrows).(E)Uncommonly,carcinomasconsistoftightlyadhesiveclustersofcells,asinthiscarcinomawithmedullaryfeatures,orwhenthereisabundantextracellularmucinproduction.(F)Suchtumorsmayappearaswell-circumscribedmassesinmammograms,mimickingtheappearanceofabenignlesion.
Mucinous(colloid)carcinomaisanER-positive/HER2negativetumorthatproducesabundantamountsofextracellularmucin.Thetumorsusuallyaresoftandgelatinousbecauseofthepresenceofmucinpoolsthatcreateanexpansilecircumscribedmass.
TubularcarcinomaisanothertypeofER-positive/HER2negativecancerandisalmostalwaysdetectedonmammographyasasmallirregularmass.Thetumorcellsarearrangedinwell-formedtubulesandhavelow-gradenuclei.Lymphnodemetastasesarerare,andtheprognosisisexcellent.
Inflammatorycarcinomaisdefinedbyitsclinicalpresentation,ratherthanaspecificmorphology.Patientspresentwithaswollenerythematousbreastwithoutapalpablemass.Theunderlyinginvasivecarcinomaisgenerallypoorlydifferentiatedanddiffuselyinfiltratesandobstructsdermallymphaticspaces,causingthe“inflamed”appearance;trueinflammationisabsent.Manyofthesetumorsmetastasizetodistantsites;theoverall5-yearsurvivalislessthan50%,andunderstandablyevenlowerinthosewithmetastaticdiseaseatdiagnosis.AbouthalfexpressERand40%to60%overexpressHER2.
Alltypesofinvasivebreastcarcinomaareassignedagradefrom1(low-grade)to3(high-grade)basedonnuclearpleomorphism,tubuleformation,andproliferation.Low-gradenucleiaresimilarinappearancetothenucleiofnormalcells.High-gradenucleiareenlargedandhaveirregularnuclearcontoursresultingfromabnormalDNAcontentandstructure.Mostlow-gradecarcinomasformwell-definedtubulesandmaybedifficulttodistinguishfrombenignlesions,whereashigh-gradecarcinomaslosethiscapacityandinvadeassolidsheetsorsinglecells.Proliferationisevaluatedbycountingmitoticfigures.ThemajorityofHER2-positiveandtriple-negativecarcinomasarehighlyproliferative,whereasER-positivecancersshowawiderangeofproliferation.