May 2, 2025 • 15 mins
On this episode of “Lab Medicine Rounds,” Justin Kreuter, M.D., speaks with Erinn Downs, D.O., professor of laboratory medicine and pathology at Mayo Clinic’s Arizona campus, on the topic of benign mimics of malignant breast pathology.
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:07):
This is Lab Medicine Rounds, a curated podcast for
physicians, laboratoryprofessionals, and students. I'm
your host, Justin Kreuter, atransfusion medicine
pathologist, assistant professorof laboratory medicine pathology
at Mayo Clinic. Today, we'rerounding with doctor Aaron
Downs, professor of laboratorymedicine pathology and anatomic
(00:27):
pathology at Mayo Clinic inArizona to guide us through the
world of benign mimics ofmalignant breast pathology.
Thanks for joining us today,doctor Downs.
Speaker 2 (00:38):
Thanks so much for the invitation to be here.
Speaker 1 (00:41):
So I wanna maybe kick off our conversation with why is
it important to appreciatemimics in breast pathology?
Speaker 2 (00:51):
Sure. You know, a lot of times we're making a
diagnosis based on a core needlebiopsy, and this is oftentimes
the patients lead off into howthey are going to be treated in
the future. So if we're talkingabout something that's benign,
this may mean that theirfollow-up may just be watchful
waiting or additional imaging.If it's something that's
(01:14):
malignant, it may mean they'regoing to go to the Operating
Room and have a procedure. Theymay need chemotherapy or even
radiation.
So we really want to make surethat we are appropriately
classifying these lesions sothat future treatment can really
be appropriate.
Speaker 1 (01:35):
Right. So it sounds like there are a lot of
different directions that thingscan go, and I'm impressed to
think about these. You weresaying, you know, it's a needle
biopsy, so it's really kind of aminimal tissue that you're
getting to evaluate thepathology in a needle.
Speaker 2 (01:51):
Correct. It is. So I think it's important to remember
that, you know, we're dealingwith a small sample of a larger
lesion. A lot of times, though,these are fairly representative
of what is going on. So thereare times when we are I would
say the majority of the time, weare actually able to render a
diagnosis and then, you know,treatment goes forward.
(02:14):
There are times, though, whenit's probably best serving the
patient to leave a diagnosis assomewhat ambiguous, and admit
that some of these lesions, wejust need to look at more
tissue. So we try really hard toget to a diagnosis, but I think
there's also some uncertainty,and uncertainty is something
(02:38):
that you have to, I think, getcomfortable with pathology.
Speaker 1 (02:41):
I think that's something I'd like to highlight
for our student listenersbecause sometimes we have people
apply for residency inpathology, and sometimes it's
with the perception that thingsare black and white in
pathology. And I think you'rehighlighting that, hey, this is
clinical medicine too. There arechallenges. So can you share a
couple of examples of where youcan have mimics maybe in either
(03:05):
direction in breast pathology?
Speaker 2 (03:08):
Sure. So there are a couple of lesions that I kind of
hold in my mind to be aware of.Something like organizing fat
necrosis, totally benign processthat we see frequently in the
breast, happen after an injury,can happen after prior surgery
or prior biopsy. So we seeorganizing fat necrosis, right?
(03:29):
That's benign lesion.
The mimic of that that ismalignant is something called an
invasive carcinoma withhistiocytoid features.
Vatnacurus has a lot ofhistiocytes, as the name
implies. Invasive carcinoma withhistiocytoid features looks like
histiocytes, and they can bereally bland and really tricky.
(03:49):
So something I learned duringresidency was kind of this whole
concept of a triple test inbreast pathology, where the
imaging has to match theclinical, and it also has to
match the pathology. So if oneof those is not adding up,
beware.
And really think about, Gee, isthis really fat necrosis, and
(04:13):
does this patient have a reasonto have fat necrosis? Or maybe
should I put a cytokeratin stainon this and make sure I'm not
missing something? That's
Speaker 1 (04:20):
sneaky For our listeners that may not be
familiar and have experiencedbreast sign out pathology, can
you elaborate about that, thatidea of this triple test about
how does that conversationhappen between what the imaging
looks like, what the pathologyis showing, what the clinical
how is that navigated inclinical medicine as an example?
Speaker 2 (04:44):
So I can think of examples when maybe the imaging
says, I've got these reallyworrisome microcalcifications
and you are cutting into atissue block and you see, you
know, well, there's a couplemicrocalcifications there, but I
don't have any real epithelialchanges associated with these
(05:05):
microcalcifications. It's reallyimportant to go and look and
correspond with the specimenimage. So when the radiologist
takes this biopsy formicrocalcifications, they
actually image those cores thatthey take, and you get an idea
of how many microcalcificationsare there. And then when you
look under the scope, you needto make sure that what you're
seeing matches what was there.So if you're not seeing many
(05:27):
microcalcifications incomparison to the specimen
image, it would really behooveyou to go deeper into that
block, that tissue block, lookat more levels and really make
sure you've accounted for that.
So that's an example of usingdata that's in Epic that we know
about the imaging to guide whatwe're doing. You know, sometimes
(05:48):
it's a conversation with theradiologist, too, that says, you
know, How concerned are youabout this lesion? Did this
lesion maybe dissipate after youtook a core needle of it? Maybe
that's a cyst. That informationwould be good to know before we
really level into a block andchase something that maybe isn't
there.
(06:09):
Versus them saying, you know,I'm really worried about this,
and we cut levels and we're justnot seeing what can account for
that mans lesion. And I think,you know, then they reconcile
that, and maybe our biopsyreally didn't sample what we
wanted it to.
Speaker 1 (06:27):
I see. So it's a nice way to verify that we got this
needle. Is this representativeof the lesion that we're going
for? Or maybe we missed it or weneed to take a different
approach to it.
see. How do you navigate that interms of training, like thinking
back to your own training inthis and doing this comparison
(06:49):
and understanding what canaccount for we have the lesion.
I guess what I'm getting at is,what's the experience of
learning how to approach andnavigate these challenging
waters of mimics?
Speaker 2 (07:06):
You know, unfortunately, sometimes it's
just life. It's time at themicroscope. I can remember when
I was a resident, I had and itwas almost near the end of my
residency, and I was going to doa breast fellowship. I had an
attending tell me, you know,you're a pretty good resident,
but just so you know, you're notgoing be really good until
you're about five years out. AndI was like, Oh, well, that's
(07:27):
really disappointing to hear.
I look back now and I understandwhat he was getting at, that it
is time in the saddle and it istime dealing with different
situations that arise. And thelonger you do this, the more you
are cognizant of the differentthings that you're going to run
(07:50):
across. So in training, you heara lot about them, and then I
think it's maybe not until youare actually faced with working
one of these lesions up that iteverything starts to fall into
place, and and you begin tolearn to work through these a
bit more.
Speaker 1 (08:26):
I've heard people sometimes talk about we don't
learn from experience, but theidea we learn from reflecting on
experience. And so I'm curious,what's your approach of
capturing the learning when youcome across one of these mimics?
And and after you navigate it,are there certain ways you're
reflecting and thinking aboutthe case? For example, maybe
(08:49):
appreciating, was there somenuanced piece of this that made
this one different than others?How do you go about that?
Speaker 2 (08:57):
So I'm always appreciative of having clinical
history. I think clinicalhistory and knowing what has
gone on with the patient isreally important, and that can
really save you from potentiallygoing down the wrong road. You
know, in breast pathology,sometimes we deal with
(09:20):
metastatic lesions to thebreast, and if you don't know
that this patient had a historyof an ovarian serous carcinoma,
then you may misinterpretsomething that looks like
micropapillary carcinoma as abreast primary. So, knowing
clinical history and having aheightened sense for this looks
micropapillary, maybe I don'thave any information on the
(09:40):
patient, Maybe I should do acouple of immunostains and just
make sure that what I'm reallydealing with this is a breast
primary. Another thing is useyour colleagues.
A lot of times, I may be goingdown a road on something and and
think I'm I'm headed in theright direction, and it's always
good to phone a friend and andshow a case around and make sure
(10:01):
that, you know, these differentsets of eyes and this different
knowledge base that's that'sthere is thinking, yeah, you're
on the right page or, man, weyou gotta do you really need to
do some other things with thiscase.
Speaker 1 (10:13):
I I think for the clinicians that are listening to
this podcast, to highlight youryour point out about knowing the
clinical history is reallyimportant. I think sometimes
people feel like, well, weshouldn't tell the pathologist
what's going on or what we'resuspicious of because we want to
have, like, an unbiased read.Right? But what would you say to
(10:34):
them just to kind of underlineand highlight your point on the
clinical information is helpful?
Speaker 2 (10:40):
Yeah. You know, pathology is not practiced in a
vacuum. That information is soimportant to know the history.
And do you run a risk that itbiases you? Sure, you do.
But you also owe it to thepatient and to yourself to
incorporate that information,not let it bias you, and then
(11:03):
prove to yourself what'shappening and what's going on,
and using the medical history tohelp you, not bias you, but to
bolster your diagnosis.
Speaker 1 (11:15):
Along those lines, I wonder, thinking about another
segment of our audience, maybethe young professionals, you
know, in those first five yearsout in practice. You mentioned
showing the case to colleagues.And what are some best practices
on how you go about showing acase to a colleague? What's a
way that you can do that thatkind of respects their time,
(11:38):
highlights what issue that yousee or question that you have?
What does that look like whenyou ask a colleague for help?
Speaker 2 (11:47):
Sure. I'm lucky. I have wonderful colleagues that
their doors are always open, Ican just walk in their office
and say, hey. Can you look atthis case? Not everybody's gonna
be in that same situation, and Ithink it's important to also
know that, you know, a lot ofpeople are busy.
So if it's reaching out andsaying, Hey, I have a case I'm
(12:07):
struggling with. Can we make atime to sit down together and
look at this? You know, beingrespectful of someone's time,
being prepared with, here arethe pertinent slides. Don't
follow-up with the two trays ofslides and say, please help me
find the microinvasion in this.Anyone with 50 trays of ductal
carcinoma and say to, you know,have a good idea going in what
(12:30):
your questions are and to showthem the the pertinent
information or the pertinentslides, but also come with the
pertinent information and andthe history that's relevant to
the case too.
Speaker 1 (12:41):
Oh, it's wonderful, wise words for the audience.
Maybe as a final question, I'mcurious on these as diagnostic
challenges. Is this a situationwhere these mimics are kind of a
static thing and we just need tokind of train to them and
they're gonna persist in being adiagnostic challenge? Or do you
(13:03):
see future, I don't know if it'simmunostains or if it's AI
technologies that may changewhat we see as a mimic?
Speaker 2 (13:13):
Sure. I think, just looking back since I've started,
I can think of examples of casesthat I would have signed out
very descriptively at one point,like low grade spindle cell
neoplasm, right, and listed whatthe differential was. Could be a
fibromatosis. The immunostainsdon't really support it, but
maybe it's a low gradefibromatosis like metaplastic
(13:34):
carcinoma. Big difference inthose two diagnoses.
Just with that as a specificexample, the thinking about that
has changed, and you canactually look for typical
molecular alteration infibromatosis and use that to
help you make that diagnosis.And then you are much more
specific in what you are callingthis low grade stem cell
(13:57):
neoplasm. And I think you aredoing a much better service to
the clinicians and frankly tothe patient as well. Because
certainly the treatment of thatlesion in particular has changed
over time. So much like ourdiagnoses in that realm have
changed somewhat over timebecause we, you know, we have
molecular data, so so has thethe treatment of them.
(14:20):
So I think molecular plays a bigrole. Certainly,
immunohistochemistry, as as newstains come on board, plays a
big role. And I would imagineyou mentioned AI. I would
imagine in the future, sure, Ithink AI will probably play a
role as well. I think we're aways from it, but I think it's I
think we're not getting awayfrom it.
Speaker 1 (14:40):
A wonderful world in pathology. We've been routing
with doctor Downs talking aboutbenign mimics, malignant breast
pathology. I really appreciateyou taking the time to talk with
us today, doctor Downs.
Speaker 2 (14:52):
Thank you so much for letting me be here.
Speaker 1 (14:54):
To all of our listeners, thank you for joining
us today. We invite you to shareyour thoughts and suggestions by
email to m c l education at mayodot e d u. If you've enjoyed
this podcast, please subscribe.And until our next rounds
together, we encourage you toconnect lab medicine and the
clinical practice througheducational conversations.
This is Lab Medicine Rounds, a curated podcast for
physicians, laboratoryprofessionals, and students. I'm
your host, Justin Kreuter, atransfusion medicine
pathologist, assistant professorof laboratory medicine pathology
at Mayo Clinic. Today, we'rerounding with doctor Aaron
Downs, professor of laboratorymedicine pathology and anatomic
(00:27):
pathology at Mayo Clinic inArizona to guide us through the
world of benign mimics ofmalignant breast pathology.
Thanks for joining us today,doctor Downs.
Speaker 2 (00:38):
Thanks so much for the invitation to be here.
Speaker 1 (00:41):
So I wanna maybe kick off our conversation with why is
it important to appreciatemimics in breast pathology?
Speaker 2 (00:51):
Sure. You know, a lot of times we're making a
diagnosis based on a core needlebiopsy, and this is oftentimes
the patients lead off into howthey are going to be treated in
the future. So if we're talkingabout something that's benign,
this may mean that theirfollow-up may just be watchful
waiting or additional imaging.If it's something that's
(01:14):
malignant, it may mean they'regoing to go to the Operating
Room and have a procedure. Theymay need chemotherapy or even
radiation.
So we really want to make surethat we are appropriately
classifying these lesions sothat future treatment can really
be appropriate.
Speaker 1 (01:35):
Right. So it sounds like there are a lot of
different directions that thingscan go, and I'm impressed to
think about these. You weresaying, you know, it's a needle
biopsy, so it's really kind of aminimal tissue that you're
getting to evaluate thepathology in a needle.
Speaker 2 (01:51):
Correct. It is. So I think it's important to remember
that, you know, we're dealingwith a small sample of a larger
lesion. A lot of times, though,these are fairly representative
of what is going on. So thereare times when we are I would
say the majority of the time, weare actually able to render a
diagnosis and then, you know,treatment goes forward.
(02:14):
There are times, though, whenit's probably best serving the
patient to leave a diagnosis assomewhat ambiguous, and admit
that some of these lesions, wejust need to look at more
tissue. So we try really hard toget to a diagnosis, but I think
there's also some uncertainty,and uncertainty is something
(02:38):
that you have to, I think, getcomfortable with pathology.
Speaker 1 (02:41):
I think that's something I'd like to highlight
for our student listenersbecause sometimes we have people
apply for residency inpathology, and sometimes it's
with the perception that thingsare black and white in
pathology. And I think you'rehighlighting that, hey, this is
clinical medicine too. There arechallenges. So can you share a
couple of examples of where youcan have mimics maybe in either
(03:05):
direction in breast pathology?
Speaker 2 (03:08):
Sure. So there are a couple of lesions that I kind of
hold in my mind to be aware of.Something like organizing fat
necrosis, totally benign processthat we see frequently in the
breast, happen after an injury,can happen after prior surgery
or prior biopsy. So we seeorganizing fat necrosis, right?
(03:29):
That's benign lesion.
The mimic of that that ismalignant is something called an
invasive carcinoma withhistiocytoid features.
Vatnacurus has a lot ofhistiocytes, as the name
implies. Invasive carcinoma withhistiocytoid features looks like
histiocytes, and they can bereally bland and really tricky.
(03:49):
So something I learned duringresidency was kind of this whole
concept of a triple test inbreast pathology, where the
imaging has to match theclinical, and it also has to
match the pathology. So if oneof those is not adding up,
beware.
And really think about, Gee, isthis really fat necrosis, and
(04:13):
does this patient have a reasonto have fat necrosis? Or maybe
should I put a cytokeratin stainon this and make sure I'm not
missing something? That's
Speaker 1 (04:20):
sneaky For our listeners that may not be
familiar and have experiencedbreast sign out pathology, can
you elaborate about that, thatidea of this triple test about
how does that conversationhappen between what the imaging
looks like, what the pathologyis showing, what the clinical
how is that navigated inclinical medicine as an example?
Speaker 2 (04:44):
So I can think of examples when maybe the imaging
says, I've got these reallyworrisome microcalcifications
and you are cutting into atissue block and you see, you
know, well, there's a couplemicrocalcifications there, but I
don't have any real epithelialchanges associated with these
(05:05):
microcalcifications. It's reallyimportant to go and look and
correspond with the specimenimage. So when the radiologist
takes this biopsy formicrocalcifications, they
actually image those cores thatthey take, and you get an idea
of how many microcalcificationsare there. And then when you
look under the scope, you needto make sure that what you're
seeing matches what was there.So if you're not seeing many
(05:27):
microcalcifications incomparison to the specimen
image, it would really behooveyou to go deeper into that
block, that tissue block, lookat more levels and really make
sure you've accounted for that.
So that's an example of usingdata that's in Epic that we know
about the imaging to guide whatwe're doing. You know, sometimes
(05:48):
it's a conversation with theradiologist, too, that says, you
know, How concerned are youabout this lesion? Did this
lesion maybe dissipate after youtook a core needle of it? Maybe
that's a cyst. That informationwould be good to know before we
really level into a block andchase something that maybe isn't
there.
(06:09):
Versus them saying, you know,I'm really worried about this,
and we cut levels and we're justnot seeing what can account for
that mans lesion. And I think,you know, then they reconcile
that, and maybe our biopsyreally didn't sample what we
wanted it to.
Speaker 1 (06:27):
I see. So it's a nice way to verify that we got this
needle. Is this representativeof the lesion that we're going
for? Or maybe we missed it or weneed to take a different
approach to it.
see. How do you navigate that interms of training, like thinking
back to your own training inthis and doing this comparison
(06:49):
and understanding what canaccount for we have the lesion.
I guess what I'm getting at is,what's the experience of
learning how to approach andnavigate these challenging
waters of mimics?
Speaker 2 (07:06):
You know, unfortunately, sometimes it's
just life. It's time at themicroscope. I can remember when
I was a resident, I had and itwas almost near the end of my
residency, and I was going to doa breast fellowship. I had an
attending tell me, you know,you're a pretty good resident,
but just so you know, you're notgoing be really good until
you're about five years out. AndI was like, Oh, well, that's
(07:27):
really disappointing to hear.
I look back now and I understandwhat he was getting at, that it
is time in the saddle and it istime dealing with different
situations that arise. And thelonger you do this, the more you
are cognizant of the differentthings that you're going to run
(07:50):
across. So in training, you heara lot about them, and then I
think it's maybe not until youare actually faced with working
one of these lesions up that iteverything starts to fall into
place, and and you begin tolearn to work through these a
bit more.
Speaker 1 (08:26):
I've heard people sometimes talk about we don't
learn from experience, but theidea we learn from reflecting on
experience. And so I'm curious,what's your approach of
capturing the learning when youcome across one of these mimics?
And and after you navigate it,are there certain ways you're
reflecting and thinking aboutthe case? For example, maybe
(08:49):
appreciating, was there somenuanced piece of this that made
this one different than others?How do you go about that?
Speaker 2 (08:57):
So I'm always appreciative of having clinical
history. I think clinicalhistory and knowing what has
gone on with the patient isreally important, and that can
really save you from potentiallygoing down the wrong road. You
know, in breast pathology,sometimes we deal with
(09:20):
metastatic lesions to thebreast, and if you don't know
that this patient had a historyof an ovarian serous carcinoma,
then you may misinterpretsomething that looks like
micropapillary carcinoma as abreast primary. So, knowing
clinical history and having aheightened sense for this looks
micropapillary, maybe I don'thave any information on the
(09:40):
patient, Maybe I should do acouple of immunostains and just
make sure that what I'm reallydealing with this is a breast
primary. Another thing is useyour colleagues.
A lot of times, I may be goingdown a road on something and and
think I'm I'm headed in theright direction, and it's always
good to phone a friend and andshow a case around and make sure
(10:01):
that, you know, these differentsets of eyes and this different
knowledge base that's that'sthere is thinking, yeah, you're
on the right page or, man, weyou gotta do you really need to
do some other things with thiscase.
Speaker 1 (10:13):
I I think for the clinicians that are listening to
this podcast, to highlight youryour point out about knowing the
clinical history is reallyimportant. I think sometimes
people feel like, well, weshouldn't tell the pathologist
what's going on or what we'resuspicious of because we want to
have, like, an unbiased read.Right? But what would you say to
(10:34):
them just to kind of underlineand highlight your point on the
clinical information is helpful?
Speaker 2 (10:40):
Yeah. You know, pathology is not practiced in a
vacuum. That information is soimportant to know the history.
And do you run a risk that itbiases you? Sure, you do.
But you also owe it to thepatient and to yourself to
incorporate that information,not let it bias you, and then
(11:03):
prove to yourself what'shappening and what's going on,
and using the medical history tohelp you, not bias you, but to
bolster your diagnosis.
Speaker 1 (11:15):
Along those lines, I wonder, thinking about another
segment of our audience, maybethe young professionals, you
know, in those first five yearsout in practice. You mentioned
showing the case to colleagues.And what are some best practices
on how you go about showing acase to a colleague? What's a
way that you can do that thatkind of respects their time,
(11:38):
highlights what issue that yousee or question that you have?
What does that look like whenyou ask a colleague for help?
Speaker 2 (11:47):
Sure. I'm lucky. I have wonderful colleagues that
their doors are always open, Ican just walk in their office
and say, hey. Can you look atthis case? Not everybody's gonna
be in that same situation, and Ithink it's important to also
know that, you know, a lot ofpeople are busy.
So if it's reaching out andsaying, Hey, I have a case I'm
(12:07):
struggling with. Can we make atime to sit down together and
look at this? You know, beingrespectful of someone's time,
being prepared with, here arethe pertinent slides. Don't
follow-up with the two trays ofslides and say, please help me
find the microinvasion in this.Anyone with 50 trays of ductal
carcinoma and say to, you know,have a good idea going in what
(12:30):
your questions are and to showthem the the pertinent
information or the pertinentslides, but also come with the
pertinent information and andthe history that's relevant to
the case too.
Speaker 1 (12:41):
Oh, it's wonderful, wise words for the audience.
Maybe as a final question, I'mcurious on these as diagnostic
challenges. Is this a situationwhere these mimics are kind of a
static thing and we just need tokind of train to them and
they're gonna persist in being adiagnostic challenge? Or do you
(13:03):
see future, I don't know if it'simmunostains or if it's AI
technologies that may changewhat we see as a mimic?
Speaker 2 (13:13):
Sure. I think, just looking back since I've started,
I can think of examples of casesthat I would have signed out
very descriptively at one point,like low grade spindle cell
neoplasm, right, and listed whatthe differential was. Could be a
fibromatosis. The immunostainsdon't really support it, but
maybe it's a low gradefibromatosis like metaplastic
(13:34):
carcinoma. Big difference inthose two diagnoses.
Just with that as a specificexample, the thinking about that
has changed, and you canactually look for typical
molecular alteration infibromatosis and use that to
help you make that diagnosis.And then you are much more
specific in what you are callingthis low grade stem cell
(13:57):
neoplasm. And I think you aredoing a much better service to
the clinicians and frankly tothe patient as well. Because
certainly the treatment of thatlesion in particular has changed
over time. So much like ourdiagnoses in that realm have
changed somewhat over timebecause we, you know, we have
molecular data, so so has thethe treatment of them.
(14:20):
So I think molecular plays a bigrole. Certainly,
immunohistochemistry, as as newstains come on board, plays a
big role. And I would imagineyou mentioned AI. I would
imagine in the future, sure, Ithink AI will probably play a
role as well. I think we're aways from it, but I think it's I
think we're not getting awayfrom it.
Speaker 1 (14:40):
A wonderful world in pathology. We've been routing
with doctor Downs talking aboutbenign mimics, malignant breast
pathology. I really appreciateyou taking the time to talk with
us today, doctor Downs.
Speaker 2 (14:52):
Thank you so much for letting me be here.
Speaker 1 (14:54):
To all of our listeners, thank you for joining
us today. We invite you to shareyour thoughts and suggestions by
email to m c l education at mayodot e d u. If you've enjoyed
this podcast, please subscribe.And until our next rounds
together, we encourage you toconnect lab medicine and the
clinical practice througheducational conversations.
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