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Anatomy and Normal Variants Premammary (subcutaneous)• zone Zonal Intralobular tissue • Interlobular tissue • Stroma/connective tissue• Glandular elements • Internal Contents • Overview Posterior suspensory • ligaments (PSL) Anterior suspensory ligaments• (ASL) of Cooper Posterior mammary • (PMF) Anterior mammary fascia• (AMF) Terminal duct lobular• unit (TDLU) Abbreviations IMAGING ANATOMY TERMINOLOGY ASL ○ May contain ectopic○ ducts and TDLU Contains subcutaneous○ fat, blood vessels, ASL Anterior margin defined○ by skin, posterior margin Most superficial zone○ Relatively lower collagen○ content Higher in cellular ○ elements and hyaluronic acid Relatively lower in○ cellular elements and hyaluronic Higher acidin collagen ○ content Nerves, blood vessels,○ and lymphatics ASL (Cooper ligaments)○ and PSL Fat, connective tissue○ Extralobular ducts ○ and TDLUs contain 2 cell layers TDLUs ○ Extralobular ducts ○ Support and mobility○ relate to fascial attachments to skin Average breast size ○ Axillary tail of Spence○ Relationship to chest○ wall Extends laterally to○ anterior axillary fold and medially to Extends from 2nd or○ 3rd intercostal space to 6th or 7th Composed of 15-20 lobes,○ each encased in fascial Conical, sheath round, or ○ hemispherical shape Formed from 2 leaflets– of AMF inserting into dermis defined byAMF Inner epithelial cell – layer Outer myoepithelial cell– layer and chestwall Median: 5 cm thick with– mammographic compression Thickness: 5-7 cm – Diameter: 10-12 cm – Extension of normal breast– tissue toward Inferior-most margin overlies– upper abdominal Lateral portion overlies– serratus anterior muscle Superior 2/3 overlies – pectoralis major muscle lateral sternum intercostal space defined byAMFandPMF oblique muscles Breast Overview ↑ false-positives, but• sensitivity retained when BPE Describe background parenchymal• enhancement (BPE) Describe fibroglandular• tissue: Fatty, scattered, Ideally performed during• follicular phase menstrual cycle Density and enhancement• features of parenchyma vary Fibroglandular tissue/muscle• often shows physiologic MR Pectoral muscles and • ribs visible as hypoechoic posterior Interlobular stroma and• glandular elements usually Echogenicity defined • relative to subcutaneous fat ASL usually visible in• subcutaneous zone Thin, echogenic skin • line: ≤ 2 mm US ↑ fibroglandular density• ↓ sensitivity of mammography American College of Radiology• Breast Imaging and Fatty involution typically• begins in lower outer quadrant Overall breast density• reflects ratio between glandular Mammography Retromammary zone • Mammary zone • ANATOMY IMAGINGISSUES moderate ormarked ↑ BPE predicts ↑ risk○ of developing breast cancer Minimal, mild, moderate,○ marked heterogeneous, extreme Less dense stroma and○ lower breast water content with patientageandphaseofmenstrualcycle enhancement structures Fibrotic tissue can○ be hyperechoic or hypoechoic hyperechoic Subcutaneous fat lobule(s)○ surrounded by ligaments can and ↑riskofdevelopingbreastcancer Density categories ○ Reporting andDatabaseSystem(BI-RADS) Progresses with age○ to upper outer quadrant Usually symmetric between○ but wide range of elements (higherdensity)andfat(lower Contains fat and PSL,○ which attach PMF to chest Defined wall anteriorly ○ by PMF and posteriorly by chest Most wallposterior of 3○ zones Subdivided haphazardly○ by interspersed ASL Contains fibroglandular○ tissue: Majority of ducts/TDLU, Defined anteriorly ○ by AMF and posteriorly by PMF present aspalpablemass(es) D: Extremely dense, which– lowers sensitivity of C: Heterogeneously dense,– which could obscure B: Scattered fibroglandular– densities A: Almost entirely fat – normal stromal fat,andconnectivetissue Usually visible on mammograms– and sonograms Provide support for breast– mammography detection ofsmallmasses 5 Anatomy and Normal Variants Fibroglandular tissue (mammary zone) Posterior suspensory ligament Retroglandular zone (fat) Pectoralis major muscle Pectoralis minor muscle Pectoralis major muscle Retroglandular zone (retromammary fat) Normal vessel Posterior suspensory ligaments Fibroglandular tissue (mammary zone) Fibroglandular tissue (mammary TOMOSYNTHESIS OF NORMAL ZONAL ANATOMY TOMOSYNTHESIS Breast Overview Breast Ducts Cooper) Fat lobules with crevices Anterior suspensory ligament Anterior suspensory ligaments (of Premammary zone (subcutaneous fat) Premammary zone (subcutaneous fat) Premammary zone (subcutaneous fat) Mammary zone (fibroglandular tissue) CC tomosynthesis of normal breast with scattered fibroglandular density shows radially arrayed ducts leading to the nipple. (Top) CC tomosynthesis of normal breast with scattered fibroglandular density shows radially arrayed a duct. Some ducts may fuse before leading to Approximately 15-20 lobes comprise the glandular portion of the breast, each leading to anatomy. an orifice in the nipple. (Middle) CC tomosynthesis shows scattered fibroglandular density and nicely depicts normal zonal (Bottom) MLO tomosynthesis shows normal zonal anatomy of the breast. 6

Anatomy and Normal Variants Retroglandular (prepectoral)zone(fat) Mammary zone(fibroglandulartissue) Premammary zone(subcutaneousfat) US OFZONALANATOMY Premammary zone,subcutaneousfat ducts. the breast:Premammary,mammary, andretromammary.(Bottom)NormaltransverseUSatthelevel ofthenippleshowssubareolar US oftherightbreast(samepatient) alongtheorientationofductsat9:00positionnear nippledemonstratesthe3zonesof (Top) RadialUSintheaxillarytail(fatty portion)ofthebreastshowspositionanteriortopectoralis muscles.(Middle)Radial Anterior suspensoryligament(of Subcutaneous fatlobule Pectoralis minormuscle Pectoralis majormuscle Fibroglandular tissue Prepectoral fat Normal duct Cooper) Lung Breast Overview Retroglandular zone Mammary (fibroglandular)zone Skin Lactiferous sinus Normal nipple Posterior suspensoryligament Normal duct 7 Anatomy and Normal Variants Main ducts Enhancement of periductal stroma showing clustered ring morphology throughout involved segment Periductal enhancement Posterior suspensory ligaments Pectoralis major muscle Pectoralis minor muscle Fibroglandular tissue Retroglandular zone Precontrast high signal showing segmental anatomy MR OVERVIEW OF BREAST ANATOMY MR OVERVIEW Breast Overview Breast with hemosiderin in nipple Duct enhancement in nipple Anterior suspensory ligament STIR hyperintense simple cyst Hypointense dots in terminal duct lobular units containing hemosiderin Precontrast high duct signal in nipple Dark tubular structure represents duct Sagittal T1 MR prior to contrast injection shows extensive high duct signal due to blood in a woman with bloody nipple discharge. (Top) Sagittal T1 MR prior to contrast injection shows extensive high duct signal due to blood in in the blood in ducts throughout (Middle) Sagittal STIR MR (same patient) shows magnetic susceptibility artifacts due to hemosiderin several segments involved by DCIS. An incidental cyst is seen. (Bottom) Sagittal T1 C+ FS MR (same patient) shows extensive segmental low nuclear grade DCIS. nonmass enhancement in a clustered ring/periductal pattern. Findings were due to extensive