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BI-RADS Assessment Categories – Overview

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The next subject I wanted to discuss is

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the BI-RADS assessment categories, which

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are very important in breast imaging.

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These are the sort of the final

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categories that are going to determine our

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management for the case or the finding.

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And it ranges from Category

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0 through Category 6.

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And Category 0 is need or needs

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additional imaging evaluation.

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Category 1 is negative.

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Category 2 is benign.

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Category 3 is probably benign.

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Category 4 is suspicious.

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Category 5, highly suggestive of malignancy.

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And Category 6 is reserved for patients

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who have a known biopsy-proven malignancy.

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So that's a special category.

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There's a likelihood of malignancy

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that's associated with each of these

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categories and that's important.

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So when we give a category number, we're

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also communicating the likelihood of

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malignancy for that case or that finding.

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So, for Category 0, really the workup isn't

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finished, there's some additional imaging that

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needs to be done, so we really can't assess a

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likelihood of malignancy if it's Category 0.

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Category one and two technically should

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be a 0% chance of malignancy.

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We know that there are some false-negative exams

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where we call it negative, but it turns out

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later that the patient has a cancer and it probably

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was that finding you called negative or benign.

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So let's say this is zero to 1%.

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Category three, which is the probably benign

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category, by definition, our likelihood of

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malignancy is supposed to be less than 2%.

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So that's a very small margin.

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You know, basically one to

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2% chance of malignancy.

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And category four is a very broad category.

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The chance of malignancy is anywhere

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from 2 to 95%, which is very large.

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For that reason, there has been some advocacy

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for dividing this up into subcategories,

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which is, uh, four A, B, and C with

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these likelihoods of malignancy.

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So 4A would be under 10%

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4B would be 10 to 50% 4C

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would be 50 to 95%, becoming a

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little bit more granular within that

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very large category. For category five,

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is a greater than 95%

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chance of malignancy.

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And category six is 100% because

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that's a patient with a known cancer.

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Management differs depending

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on the category as well.

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So category zero usually means

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something else needs to be done.

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And if we're using this for MRI, which is pretty

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unusual, it means that a repeat exam is needed.

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And it might be that the patient wasn't

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able to complete the exam or the contrast

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extravasated, and that wasn't noticed,

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or there was a lot of motion on the

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exam and it's technically inadequate.

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Something like that.

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So usually category zero is for a technical

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problem on MRI, where we would repeat

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the full exam. For category one and two,

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we're going to return to routine follow

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up, whatever that is for the patient.

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It might be that they go back to clinical

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follow up and screening mammography.

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If they're an average risk person, it

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might be annual high-risk screening

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MRI, if they're a higher risk person.

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Category three, we usually recommend a six-month

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follow-up after a category three recommendation.

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BI-RADS category four and five, that's

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the suspicious and sort of highly suggestive

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of malignancy categories, we're going

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to recommend biopsy for those patients.

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And category six, that's a known

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malignancy with the caveat that it's a

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known malignancy and we also don't need

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to do any further evaluation or biopsy.

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So category six is just the malignancy

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and nothing else recommended.

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So for BI-RADS one and two, we're

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going to do routine follow-up.

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That would include clinical follow-up

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for symptoms that could even be surgical

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consultation for symptoms, but it just

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means that we're not really seeing anything

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that's explaining the problem on the MRI.

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It might mean going back to screening

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or diagnostic mammography, depending

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on what's recommended and annual

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breast MRI, depending on patient risk.

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BI-RADS 3

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is a little bit of a controversial area.

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There has been some discussion in the literature

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about this, but we don't have very clear

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guidelines about when BI-RADS 3 can be used.

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It has been suggested based on literature

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review that BI-RADS 3 can be used on

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baseline or high-risk screening exams

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for a unique focus that's not T2 bright.

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So T2 bright, we would call it benign.

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But if it's not T2 bright and it's unique,

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a mass with all the features of

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fibroadenoma could be a BI-RADS 3.

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I would argue that MRI is a very expensive

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exam to do follow-up of a fibroadenoma

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and that might be better accomplished with

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ultrasound if the area is visible by ultrasound.

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Also, patients who are BRCA gene mutations,

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some patients will develop cancers that

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have a very benign appearance to them.

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So this would not include

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patients who are BRCA positive.

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And then focal or regional non-mass

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enhancement that's not T2 hyperintense.

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So T2 hyperintense, we would probably

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let go as benign, but if it's not T2

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hyperintense, we may be able to follow

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it, especially if it's on a baseline.

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And then in 2021, there's been a lot of

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literature about enlarged axillary lymph nodes

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related to the COVID-19 vaccine.

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And we've seen a lot of this this year.

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So, BI-RADS 3 is being suggested when we see

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large axillary nodes in the setting of a

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recent COVID-19 vaccine to that same arm.

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And, you know, the recommendation usually

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is that we follow up in six to eight weeks

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with an axillary ultrasound, not another

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MRI, with the hope that the axillary nodes

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have decreased to normal size by that time.

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I will say that in practice, we

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also use BI-RADS 3 for some other

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scenarios, even though it may not be

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completely supported in the literature.

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And these include probable background

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enhancement, especially if it's

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unusual or asymmetric patterns.

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And we saw that earlier with one of

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our patients that we looked at, patients

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with probably evolving fat necrosis.

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Sometimes this can mimic a lot of other things.

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There can be some enhancement.

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It can be a little uncertain that

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what we're looking at is fat necrosis.

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If we feel like we can make a

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definite diagnosis, we will do

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that and give it a BI-RADS 2.

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If it's questionable, we may

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recommend a follow-up.

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And then the same with some types

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of post-operative enhancement.

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We definitely see a lot of patients who

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have had an excisional biopsy or lumpectomy.

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Sometimes their enhancement pattern is a little

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bit unusual after those surgical changes,

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and we may follow them closely for a while.

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And management for BI-RADS 3 patients

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includes a follow-up MRI at six

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months, 12 months, and 24 months.

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and then return to routine follow-up

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if the finding resolves.

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IREDS 4 and 5, these are patients

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where we're recommending a biopsy.

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So the first thing to decide when we're

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reporting this is the modality for biopsy.

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So does this require MRI biopsy?

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Do we think we can see it on an ultrasound

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and therefore do an ultrasound biopsy?

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So there are some things to consider.

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So for larger lesions, it may be

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useful to consider a second-look

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ultrasound with the intent to biopsy by

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ultrasound if a lesion is discovered.

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And then, if you're going to make that

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recommendation, in your report, you

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have to clearly indicate your plan if

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the lesion is not seen by ultrasound.

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Are we thinking that this might

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be a BI-RADS 3 MRI with follow-up

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if we don't see the lesion on MR?

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On ultrasound, or are we definitely

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going to need an MRI-guided biopsy?

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And those are things that you don't want to

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leave to your colleague to try to sort out

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on the day of their second-look ultrasound,

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you want to think about that beforehand.

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And then for smaller things, very small

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foci, small masses, non-mass enhancement,

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we usually will go right to MRI biopsy.

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The other thing to consider is:

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Whether you need a unilateral

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or bilateral biopsy.

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Right now we're doing biopsies from a lateral

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approach. If they're bilateral, because

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we can't access the medial aspect of the

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breast if both breasts are in the biopsy

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coil, we would have to come from lateral.

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So you have to consider some of those

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logistics. Like, can you access the things

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you want to biopsy from a lateral approach?

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If you need a medial approach, then

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maybe you'd need to do both breasts

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separately or just one breast.

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So we need to consider the number of biopsies

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and the logistics and timing.

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Often we can do bilateral biopsies all

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in the same day; sometimes it takes two

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appointments, so just something to keep in mind.

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And then BI-RADS 6, we're going to use

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this for patients with a known breast

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malignancy, so that's a recent diagnosis,

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not a past diagnosis, and they have no

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additional findings that require a biopsy

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or further workup.

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So BI-RADS 6 is sort of a special category.

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The standardized BI-RADS lexicon really helps us

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with assessment of findings and communication.

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And the BI-RADS descriptors help guide the

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radiologist to the appropriate BI-RADS category.

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The BI-RADS categories are associated with

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management, and that's sort of definite,

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this BI-RADS category equals this management.

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And then the BI-RADS assessment

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categories help us to clearly communicate

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the next steps to both our imaging

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colleagues and the referring providers.

Report

Description

Faculty

Lisa Ann Mullen, MD

Assistant Professor; Breast Imaging Fellowship Director

Johns Hopkins Medicine

Tags

Women's Health

MRI

Breast

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