The ACR BI-RADS US subcommittee developed a US lexicon to describe US findings in a manner that is standardized, clear, and concise (Table 5.1). Use of the terminology in the ACR BI-RADS lexicon helps standardize assessments, reduce confusion in inter- pretation and reporting, trigger appropriate management recom- mendations, and guide principles of an audit.
Tissue Composition
As in mammography and magnetic resonance imaging (MRI), US can depict the many variations in breast tissue composition.
According to BI-RADS fifth edition for mammography, loosely correlating with the four densities are three US categories:
homogeneous background echotexture—fat; homogeneous background echotexture—fibroglandular; and heterogeneous background echotexture.
The proportion of fat-to-fibroglandular parenchyma varies widely in the normal population variably dependent on the patient’s age, hormonal influences, and individual characteristics.
In young women the breast tissue is composed predominantly of fibroglandular tissue; in older women, breast tissue has a greater proportion of fat. However, there are substantial individual variations.
In breasts with homogeneous background echotexture—
fat, most of breast tissue is occupied by oval fat lobules sur- rounded by a thin rim of connective tissue or Cooper’s liga- ments, which provide connective tissue support for the breast from the posterior layer of superficial pectoral fascia to the superficial layer lying just beneath the skin (Fig. 5.13). Breasts with homogeneous background texture—fibroglandular have a thick zone of homogeneously echogenic fibroglandular parenchyma beneath a layer of subcutaneous fat of variable thickness (Fig. 5.14). Many lesions, both benign and malignant, arise within the fibroglandular zone or at its junction with the layer of fat.
Heterogeneous background echotexture is characterized by multiple hyperechoic and hypoechoic areas, which can be focal or diffuse (Fig. 5.15). Heterogeneous parenchyma may con- found interpretation of small hypoechoic areas of fat with small hypoechoic masses.
Masses
The BI-RADS lexicon suggests standardized reporting for masses using feature analysis. A mass has three dimensions and occupies space. It should be seen in two planes on two-dimensional imag- ing and in three planes with volumetric acquisitions. Using mul- tiple sonographic descriptors when describing a mass increases specificity and diagnostic confidence. The three most important feature categories, taken together for assessment of likelihood of malignancy, are shape, orientation, and margin. Additional
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FIG. 5.4 Color Doppler versus power Doppler. (A) The color flow sensitivity setting is inadequate and the compression with the probe is too great, occluding the small vessels in the mass. (B) The appropriate corrections have been made to sensitivity settings and compression. The vessels within the mass are now seen. (C) Amplitude-based power Doppler image shows vessels in pattern similar to that in (B) with a greater number depicted. Flow direc- tion cannot be determined on power Doppler, but its sensitivity is higher than that of color flow. Mass containing small cysts and some calcifications is a biopsy-proven radial. (Copyright by Ellen B. Mendelson, MD, FACR.)
FIG. 5.5 Color flow Doppler: vessels in rim. Circumscribed 6-mm mass with rim and peripheral vascularity diagnosed as abscess.
(From Mendelson EB, Böhm-Vélez M, Berg WA, et al: ACR BI-RADS® Ultrasound. In ACR BI-RADS® atlas, breast imaging reporting and data system. Reston, VA, 2013, American College of Radiology.
Copyright by Giorgio Rizzatto, MD.)
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FIG. 5.6 Shear wave elastogram of a biopsy-proven invasive ductal carcinoma seen in the upper half of the im- age shows predominantly red, orange, and yellow colors at the stiff end of the color scale. B-mode image is seen in the lower half, and it shows a tiny irregular mass that might easily have been overlooked. (Copyright by Ellen Mendelson, MD, FACR.)
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FIG. 5.7 Shear wave elastogram of benign mass boxed in the upper half of the image is all blue, soft, and distinctly recognizable through the blue overlay. B-mode image is seen in the lower half, and histopathology is apocrine metaplasia and microcysts. BI-RADS assessment in this case was category 3, probably benign, and the patient requested biopsy rather than follow-up. (From Mendelson EB, Böhm-Vélez M, Berg WA, et al: ACR BI-RADS® Ultrasound. In ACR BI-RADS® atlas, breast imaging reporting and data system. Reston, VA, 2013, American College of Radiology. Copyright by Ellen B. Mendelson, MD, FACR.)
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FIG. 5.8 Three-dimensional gray scale ultrasound (US) demonstrates architectural distortion. Coronal view (A) from automated whole-breast US demonstrates three masses (circles). The superior mass is irregular (C; arrow) and the two adjacent masses are oval (B; arrows) on the axial views. (Copyright by Ellen Mendelson, MD, FACR.)
Nipple and
subareolar musculature Pectoralis
major Pectoral fascia Mammary fat Cooper’s
(suspensory) ligaments
Subcutaneous fat Montgomery’s
gland Ampulla
Lactiferous duct Acini (alveoli)
Interlobular connective tissue
Intralobular connective tissue
Superficial fascia
Subcutaneous fat Areola Montgomery’s tubercules Nipple
Mammary fat
Ampulla (lactiferous sinus) Lactiferous ducts
Acini (alveoli) with parenchyma removed
Cooper’s (suspensory) ligaments
Lobules
A Lobe
B Interlobular connective tissue
Anatomy of the Breast
FIG. 5.9 Schematic of normal breast anatomy. (A) Diagram of a breast of a woman in supine (ultrasound [US]) posi- tion. (B) Anatomy of the breast in coronal plane, which is important view in automated US systems. (Netter medical illustration used with permission of Elsevier. All rights reserved.)
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FIG. 5.10 Anatomy: normal breast. Skin, subcutaneous fat, fibroglandular parenchyma, Cooper’s ligaments, and pectoralis muscle on extended field of view of a normal breast. (Copyright by Ellen Mendelson, MD, FACR.)
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FIG. 5.11 Anatomy: normal axillary lymph node. Transverse (A) and longitudinal (B) view of a lymph node of normal size, cortical thickness, and echogenic hilum resembles a miniature kidney. (C) Normal axilla. Pec- toralis major is shown anterior to pectoralis minor with axillary vein deep to both. Nodal levels are defined relative to the pectoralis minor, level I lateral to it, level II between the muscles, and level III, deep to it.RT, right. (From Mendelson EB, Böhm-Vélez M, Berg WA, et al: ACR BI-RADS® Ultrasound. In ACR BI-RADS® atlas, breast imaging reporting and data system. Reston, VA, 2013, American College of Radiology. Copyright by Ellen B. Mendelson, MD, FACR.)
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FIG. 5.12 Anatomy: normal breast bud in female adolescent. The breast at puberty resembles gynecomastia with hypoechoic tissue immediately posterior to the nipple. Because these young patients ordinarily do not undergo mammography, it is important not to misinterpret the hypoechoic retroareolar breast bud as an abnor- mality requiring biopsy. This area should be recognized as normal for this age group and if removed surgically, the breast will not develop. (From Mendelson EB, Böhm-Vélez M, Berg WA, et al: ACR BI-RADS® Ultrasound. In ACR BI-RADS® atlas, breast imaging reporting and data system. Reston, VA, 2013, American College of Radiology.
Copyright by Helmut Madjar, MD.)
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