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Mammographic Asymmetries and Masses - Overview

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In this lesson, we're gonna talk about,

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uh, mammographic asymmetries and

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masses, their imaging characteristics.

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As you might remember, uh, BI-RADS

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provides some definitions of

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asymmetries that are slightly different.

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An asymmetry by itself is an area of fibroglandular

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density that is visible on a single mammographic

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projection—CC, MLO, something like that.

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It's typically superimposed fibroglandular tissue

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that needs to be worked up a little bit further.

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A focal asymmetry, in contrast, is a relatively

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small amount of fibroglandular density

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tissue over a confined portion of the breast.

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It has similar shape on different

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mammographic projections,

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convex outward borders, and

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usually with interspersed fat.

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And this we see on two views, right?

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So asymmetry and focal asymmetry are very

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closely related, um, but differ based

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on how many views you see them on.

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A developing asymmetry,

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although similar in name to our standard asymmetry,

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is actually more like a focal asymmetry, um,

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because it's a focal asymmetry that is new, larger,

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or more conspicuous than that on prior exams.

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So by definition, developing asymmetry

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can only be identified in patients who

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have prior imaging exams to compare to.

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So basically, a developing asymmetry is a focal asymmetry

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that is increasing or changing in some way.

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In table format, we can see some differences.

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Uh, between—here again, I've noted that the

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main difference between asymmetry and focal

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asymmetry is how many views you see it in.

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Asymmetries tend to have—at least when

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a lot of this research was done—uh,

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have a very low risk of malignancy.

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If it is malignancy, it's more likely A-L-C or I-L-C.

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Focal asymmetries have a 0.5 to 1% likelihood

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of malignancy without other features.

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This can be—just so we're aware—a reasonable

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BI-RADS reinterpretation. That would be a focal

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asymmetry without an ultrasound correlate.

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A global asymmetry, which I didn't mention before,

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um, is relatively rarely used in clinical

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practice, but it's a large amount—greater than

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one quadrant—of fibroglandular density tissue.

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Usually, it's just a normal variant or variant

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fibroglandular tissue in the breast.

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Usually not anything to worry about, and

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I would say most people probably just

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interpret this as negative or benign.

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Again, developing asymmetries—

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focal asymmetry that is new.

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The important thing about this is

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that the developing asymmetries,

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a pretty good chunk of them are

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found out to be malignant—about 15%—

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and certainly warrant further workup.

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This case is demonstrating a focal asymmetry.

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We see this area of fibroglandular density tissue.

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We see it in two views.

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It's in the lateral and upper part of the

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right breast, probably about 10 o'clock.

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Now, of course, this one I think would really

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border on the idea of a global asymmetry, right?

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It's almost full quadrant.

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Um, you could make the argument this is

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either a very large focal asymmetry or a

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global asymmetry.

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Um, but it demonstrates some of the important features

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of focal asymmetry, meaning that there's some concave

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margins, there's some interspersed fat, kind of

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looks like what we would just call normal tissue.

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Now, of course, if this is small and focal,

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um, stands out from the rest of the glandular

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tissue, then we'd wanna work it up further.

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In this case here, I'm demonstrating a developing

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asymmetry in the superior part of the left breast.

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On this MLO view, we see the small asymmetry here.

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Now, I'm not showing you the CC

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views, but they were similar.

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Um, that's why we saw it on the CC views.

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And so we can call it a focal asymmetry.

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And if we look at this exam, this is, let's say, um,

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an exam from several years ago.

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This is maybe one, two years ago,

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and this is our current exam.

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We see that this focal asymmetry

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is getting larger in size.

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This was subsequently biopsy-proven ductal carcinoma.

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Now we know that we have the overall

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decreased recall rate for tomosynthesis.

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Um, and this is particularly true for asymmetries.

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DBT has an increased ability to decipher

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normal superimposed dense tissue from a true

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lesion, um, leading to a lower recall rate for

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asymmetries on tomosynthesis screening exams.

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True lesions are ones that persist.

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Uh, even on DBT, should be further

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evaluated with diagnostic mammogram.

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Possible ultrasound—we can do spot compression

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tomosynthesis that can help assess

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the possibility of tissue superimposition.

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You can also do rotated spot compression views,

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um, which can sometimes help sort of really

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get a good view of that superimposed tissue.

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Sort of separate the tissues even a little further.

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Um, one-view asymmetries can be better

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localized for additional mammographic

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views. With DBT, of course, we can use that

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sort of imaging stack scroll bar to help us.

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It has some challenges, as we mentioned

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in previous lessons, um, but you can use

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it to help you identify a particular area.

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For masses,

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uh, BI-RADS defines a mass as a three-

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dimensional object that occupies space,

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completely or partially convex outward borders.

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In distinction with focal asymmetry, it's denser at

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the center than the periphery, and like a focal asymmetry,

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it's seen on two different mammographic projections.

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We wanna describe a few things when we see a

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mass—that includes the shape, margin, and density.

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And here we show a good example

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of a classic sort of mass, right?

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In this right breast,

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we have a CC and MLO view.

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We see this very large, uh, oval mass.

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It has some circumscribed margins,

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maybe a few indistinct margins.

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Um, and one of the associated findings

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in this mass are these prominent, uh,

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fine pleomorphic calcifications. Of course,

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when we see those associated with a mass,

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this raises our suspicion for malignancy

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quite a bit. And we can see that this

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mass is already biopsied previously, and

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we can see the biopsy marker clip here.

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Again, a smaller demonstration of a mass.

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Here we're showing left CC and

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left MLO views in the lateral,

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lower aspect of the left breast.

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So this would be approximately maybe four

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o'clock on the left—something like that.

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Um, we see this irregular mass.

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It's got spiculated margins, and it's

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high density compared to the rest of

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the fibroglandular tissue.

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Now, of course, this is sort of your

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classic malignancy, right?

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Um, got those spiculated margins.

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Um, and this was biopsied—Invasive Ductal Carcinoma.

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Um, masses are particularly

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well visualized on DBT.

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Um, we can remove the layer of

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those superimposed dense tissue.

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Um, we can see the margins a little bit better.

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Um, this can help us in the setting

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of multiple bilateral masses

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to put that into the benign category.

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We can also have improved detection

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of small spiculated masses.

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We can see those margins better.

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It's not hidden amongst that dense tissue,

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which helps improve our ability to

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identify those really tiny cancers

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that are more likely gonna be node-negative.

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Um, we get better margin analysis, and may

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improve localization for subsequent ultrasound exams.

Report

Faculty

Ryan W. Woods, MD, MPH

Assistant Professor of Radiology

University of Wisconsin School of Medicine and Public Health

Tags

Women's Health

Ultrasound

Tomosynthesis

Oncologic Imaging

Mammography

Breast

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