Lesionsofinterlobularstromaaremonophasic(onlycomprisedofmesenchymalcells)andincludebenignsofttissuetumorsfoundelsewhereinthebody,suchashemangiomas(Chapter10)andlipomas(Chapter21).Theonlymalignancyderivedfrominterlobularstromalcellsofnoteisangiosarcoma(Chapter21),whichmayariseinthebreastafterlocalradiother-apy.Themorphologiesoftheselesionsaredescribedelsewhere.
The majority of benign epithelial lesions are incidental findings detected by mammography. Their major clinical significance is their relationship to the subsequent risk of developing breast cancer. Benign changes are divided into three groups, nonproliferative disease, proliferative disease without atypia, and proliferative disease with atypia, each associated with a different degree of breast cancer risk (
Table 19.6
Nonproliferative disease is not associated with an increased risk of breast cancer.
Proliferative disease without atypia encompasses polyclonal hyperplasias that are associated with a slightly increased risk of breast cancer.
Proliferative disease with atypia includes monoclonal “precancers” that are associated with a modest increase in the risk of breast cancer in both breasts; overall, 13% to 17% of women with these lesions develop breast cancer.
MORPHOLOGYNonproliferativediseaseconsistsofthreemajormorphologicchanges:cysts,fibrosis,andadenosis.Itistermed“nonproliferative”becausethelesionscontainsinglelayersofepithelialcells.Themostcommonnonproliferativebreastlesionsaresimplecystslinedbyalayerofluminalcellsthatoftenundergoapocrinemetaplasia(
Fig.19.25A ).Theapocrinesecretionsmaycalcifyandbedetectedbymammography.Whencystsrupture,chronicinflammationandfibrosisinresponsetothespilleddebrismayproducepalpablenodularityofthebreast(so-called“fibrocysticchanges”).Proliferativediseasewithoutatypiaincludesepithelialhyperplasia,sclerosingadenosis,complexsclerosinglesion,andpapilloma.Eachisassociatedwithvaryingdegreesofepithelialcellproliferation.Forexample,inepithelial
Fig.19.24Intralobularstromalneoplasms.(A)Fibroadenoma.Thisbenigntumorhasanexpansilegrowthpatternwithpushingcircumscribedborders.
(B)Phyllodestumors.Proliferatingstromalcellsdistorttheglandulartissue,formingcleftlikespaces,andbulgeintosurroundingstroma.
http://ebooksmedicine.net
Table19.6FactorsAssociatedWithDevelopmentofInvasiveCarcinoma
Womenwithnoriskfactors1.03% 1.2–9.04%–30%
Germlinetumorsuppressorgenemutation(e.g.,BRCA1 mutation)2.0–45.06%to>90%
Ageatmenarche<12years1.34%
Ageatmenopause>55years1.5–2.05%–6%
Firstlivebirth<20years(protective)0.51.6%
Firstlivebirth20–35years1.5–2.05%–6%
Firstlivebirth>35years2.0–3.06%–10%
Neverpregnant(nulliparous)3.010%
Breast-feeding(slightlyprotective)0.82.6%
Proliferativediseasewithoutatypia1.5–2.05%–6%
Proliferativediseasewithatypia(ALHandADH)4.0–5.013%–17%