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Hello, and welcome to Noon conferences hosted by MRI Online.

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In response to the changes happening around the world and

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the shutting down of in-person events, we have decided to

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provide free noon conferences to all radiologists worldwide.

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Today, we're joined by Dr. Ania Kielar on renal masses.

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She's an abdominal radiologist at the Joint

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Department of Medical Imaging in Toronto, Canada.

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She's on the executive board of the Canadian

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Association of Radiologists currently.

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The treasurer and associate editor for abdominal

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radiology and in the writing group for version

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2021 of the ACR LI-RADS. Her areas of research,

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uh, interests include standardization

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and error reduction in radiology.

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She has 99 peer-reviewed publications

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and has published nine— 16 book chapters.

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Reminder that we'll have a little

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time at the end for a Q&A session.

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Please use the Q&A feature to ask all of your questions

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and we'll get to as many as we can before our time is up.

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That being said, thanks for joining us today. Dr. Kielar,

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I will let you take it from here.

0:52

So, thanks very much for joining me today.

0:55

Uh, my name is Ania Kielar, and my talk is on renal masses.

0:58

And I'd like to thank my friends and colleagues,

1:00

Nicola Schieda from the University of Ottawa and Satheesh

1:03

Krishna from the University of Toronto at JDMI

1:05

with me for help on this talk.

1:08

Um, I just want to clarify, I'm now

1:10

the vice president of the CAR.

1:11

Not that it matters, but it's a progression from

1:14

the, uh, previous role that I had as treasurer.

1:17

And the treasurer is working very hard,

1:19

and I don't want to take away from her.

1:20

Her work.

1:22

So, I have no disclosures related to this talk.

1:26

So we're going to try to characterize some

1:28

common renal masses that you may identify, uh,

1:31

incidentally or during workup of a renal mass.

1:35

We'll also try to create a differential diagnosis

1:37

for less common renal masses, knowing that biopsy may

1:40

still be required, and we will try to apply some sort

1:44

of standardized approach to workup of renal masses.

1:48

So we know that cysts are very common in the

1:50

population, and at least 40%, I would say,

1:53

probably more than, uh, in the population I look

1:56

at, but 40% of people have at least one cyst.

2:00

Most of the time,

2:00

we can characterize them as being benign and move on.

2:04

And we know that Bosniak classification for cystic renal

2:07

lesions has been updated in 2021, and it's supposed

2:10

to help with management, and it goes from one to four.

2:13

I'm not going to go through all of the Bosniak

2:15

classification, as I'm sure you can look that up,

2:17

or may have heard a talk on this here previously,

2:21

but there are still some lesions that can be.

2:24

Challenging despite the Bosniak classification.

2:27

So this would include small cystic lesions

2:30

because they can mimic solid nodules.

2:32

And that's particularly true on CT, less so on, uh, MRI.

2:37

But even ultrasound, if you have a cyst that has very

2:40

small septations, we see those a lot in the thyroid.

2:43

They can be tough to know if they're solid or cystic.

2:47

There are some benign nodules that do

2:49

overlap with malignancy, uh, appearance.

2:51

So you will need to do additional interventions in

2:54

those cases, and I'll show you some examples of those.

2:57

And of course, metastases and lymphoma

3:00

may present focally in the kidney.

3:01

So just because we see a primary renal lesion,

3:04

it doesn't mean that it's from the kidney

3:06

itself, and it's not something more systemic.

3:10

And finally, we know that renal malignancy subtyping

3:13

may allow for prognostication and best management,

3:16

and we'll go through that a little bit as well.

3:20

So.

3:21

In terms of complex, solid, and cystic lesions.

3:23

Here's just an example of a 59-year-old woman who presented

3:27

with some flank fullness, and we can see on these coronal

3:30

T2 image, uh, uh, with and without fat saturation.

3:34

Then we have axial images here.

3:37

Uh.

3:38

Pre- and post-contrast, we can

3:40

see that there is a large mass.

3:42

It is very septated.

3:44

It is not causing hyper necrosis, but

3:47

we can see that there are some septate.

3:49

Now there's a tiny bit of motion artifact, and the

3:51

question is, you know, are they three millimeters?

3:52

Are they four millimeters?

3:54

Using subtraction imaging is very helpful to determine if

3:57

they actually are enhancing, but even that can sometimes

4:00

be tricky if the patient breathe differently between the

4:02

uh, pre-contrast and the post-

4:04

contrast when you do subtraction.

4:06

Nevertheless, we know that this is a complex

4:08

cystic lesion, and the final diagnosis was the

4:11

cystic renal neoplasm of low malignant potential.

4:14

So resection was probably the right answer in this case.

4:18

4:21

So most complex, solid, and cystic renal lesions

4:24

are characterized as Bosniak three or four based

4:26

on that characterization, and they're generally

4:29

recommended to have surgical resection, but of

4:31

course, it depends on the patient condition.

4:35

We also know that not all cystic renal lesions can

4:38

be accurately characterized by Bosniak because things like

4:41

benign multilocular cystic nephroma, those are typically

4:44

we think of, you know, young boys and middle-aged women.

4:49

They're benign, but they have multiple septae, and

4:51

they can look like category three, sometimes two F,

4:54

but three for sure. Other ones that can often look

4:58

like at least category three are

5:00

the mixed epithelial stromal tumors.

5:02

And I'll show you an example of that as well.

5:05

And then there are other things that are actually not coming

5:07

from the kidney, and so they're not even renal in origin, so

5:10

you wouldn't want to use Bosniak classification for those.

5:13

Uh, and those would include things like perirenal lymphomas.

5:16

Now, usually the lymphoma is not actually in

5:19

the kidney, but it can end up in the renal pelvis.

5:22

Uh, perirenal hematomas and lipomas.

5:27

Here is an example of a 63-year-old woman who

5:31

had an incidentally discovered renal cystic mass.

5:33

She came for ultrasound of something totally different.

5:36

She ended up having a CT, so the top three images are

5:40

pre-contrast arterial and, um, nephrographic phase.

5:43

And then she ended up having an MRI as

5:45

well, which in both types of, uh, images.

5:49

Imaging modalities, we can see that

5:51

there's a multiloculated cystic lesion.

5:54

The MRI is quite helpful for looking at the septations,

5:57

which on the CT, especially if you look at the

6:00

nephrographic phase, it's really hard to know

6:02

if these are actually solid nodules or if they're

6:04

all just septate and there's volume averaging.

6:08

So in this case, this

6:10

post-contrast MRI is helpful, but even so, you can see there

6:14

are a lot of septations. Maybe there's some components that

6:17

are a little bit thicker septation, and so this was still

6:21

considered worrisome, and she ended up having a resection.

6:24

So we see the pathology here.

6:25

There are lots of thin walls, um, and there's no, no

6:30

lipid component.

6:31

When they did magnification views, there was no,

6:33

uh, unusual nuclei or abnormal proliferation of

6:36

them, and this was a mixed epithelial stromal tumor.

6:40

These are almost exclusively in women, and they

6:42

do have a benign course, but unfortunately,

6:45

because of their appearance, it's often very

6:47

hard to prospectively try to diagnose this.

6:52

Here's just another example where you wouldn't

6:54

want to use a Bosniak classification because

6:56

it's actually not coming from the kidney.

6:58

So the question is, uh, there we have black

7:01

arrows on the axial and coronal T2-weighted

7:03

images, and then we have white arrows.

7:05

So, uh.

7:07

The thing that's white, the white arrows, those could

7:10

be parapelvic cysts, but it's important to scroll

7:13

through your images back and forth to tell whether or

7:15

not this actually communicates with this other cystic

7:18

structure, which is in close contact with the kidney.

7:21

So this patient had a lymphangioma and parapelvic

7:23

cysts, but occasionally the lymphangioma can sort

7:25

of insinuate towards the renal pelvis, which makes

7:28

it even more challenging to know where the origin is.

7:34

Here's another condition.

7:35

It's considered not a malignancy, but this

7:38

is a big problem, and it's an emergency.

7:41

So this is an example of a patient who had pyonephrosis,

7:43

so severe distension of the kidney collecting

7:48

system, where you look at the black arrow on the

7:50

left image, there's actually a fluid-fluid level.

7:53

It's subtle, but if you change the window level,

7:55

you'll notice that, and that's the pus that's sort of

7:58

accumulating in the dependent portion of the kidney.

8:01

You can also see on the axial image

8:03

that there is some stranding anteriorly.

8:05

So this, there was a calyceal rupture associated

8:08

with this, and this patient was, you know, very ill.

8:10

They were septic, and they required urgent

8:13

urology or IR consideration for drainage.

8:18

So in terms of our solid, so I talked about cystic first,

8:21

and now we're going to move on towards the solid benign masses.

8:27

So first we have to think about things like pseudotumors.

8:30

So they're not actually masses per se.

8:33

They can look like a mass, but they're not

8:34

due to any sort of, um, proliferating tissue.

8:38

So that includes focal pyelonephritis,

8:41

renal infarction, dromedary hump, which is just a

8:45

normal outline of the kidney, but sometimes

8:48

they can stick out a little bit more acutely and

8:52

kind of cause questions as to whether that's

8:54

benign or if there's an actual tumor there.

8:56

Usually the best thing for dromedary hump

8:58

is to follow the thickness of the cortex.

9:01

And if it's about the same where it's sticking

9:03

out, uh, then it's probably a dromedary hump.

9:06

And the other thing about dromedary humps

9:08

is that they typically have the same imaging

9:10

characteristics on all sequences and all

9:13

imaging modalities as the rest of the kidney.

9:16

That, that is the renal parenchyma.

9:18

Cortical fetal lobulation.

9:21

Similarly, like a dromedary hump, will have the

9:23

same imaging characteristics as the rest

9:24

of the cortex on all imaging sequences.

9:27

No matter what imaging modality you're used using.

9:30

Other renal pseudotumors, uh, renal vein thrombosis.

9:34

So, you know, the, the.

9:36

Thrombus itself is, is one thing, but sometimes the

9:39

kidney can get enlarged temporarily, and you may actually

9:42

think that it's lymphoma or something like that, or

9:44

maybe you might think it's an RCC with tumor thrombus.

9:47

So it's important to differentiate that.

9:49

I have an example to show you, XGP.

9:52

Uh, we've probably all seen those, but there's

9:54

some calcification associated with it, usually.

9:57

And then often, if it's been there for a long

9:59

time, you have some atrophy of the cortex

10:01

associated with the calyx that's affected.

10:04

And then some people are born with

10:06

cross-fused ectopia or a pelvic kidney.

10:08

Occasionally, they're also malrotated,

10:10

and they can look weird.

10:11

So, number one, you know, do you have two normal kidneys?

10:15

And if not, is it possible that it's an, an just

10:18

an anomaly for, uh, that's how they were born?

10:22

It's not a tumor.

10:23

Now there are benign neoplasms that we should be aware of.

10:27

Some of them we can definitely tell the difference from

10:29

a malignant, and sometimes they can be pretty challenging.

10:32

So lipid-poor AMLs are one of those challenging

10:34

ones, and I'll show you some tips and tricks,

10:37

but other ones to be aware of are oncocytoma,

10:39

also can be confused with chromophobe RCC.

10:42

Lipomas, rare, but they can happen.

10:46

Uh, metanephric adenomas.

10:49

Hemangiomas, leiomyomas, and solitary

10:52

fibrous tumor in other body parts.

10:55

Hemangiomas are often called solitary fibrous

10:58

tumor now, so that's an area that might be in flux.

11:03

Even if it's not a mass, and even if it's benign, there

11:06

are certain indications that there are certain indi—

11:08

uh, diagnoses, which are still medical emergencies.

11:11

So I showed you the pyonephrosis a moment ago, but even

11:14

focal pyelonephritis can be, you know, uh, life-threatening.

11:18

Infarct, again, you want to know why they have an infarct.

11:21

Are they hypercoagulable?

11:23

Do they have a cardiac growth

11:25

that's, you know, sending off emboli?

11:27

Uh, and of course, renal vein thrombosis is not a good

11:30

thing to have because it can affect the kidney long term.

11:33

And also the question is, why are they hypercoagulable?

11:37

So here's just an example, a patient

11:39

with acute renal vein thrombosis.

11:41

So we can see on the axial images that there's still

11:44

an outline of the renal vein here a little bit,

11:46

but it's definitely not enhancing like it should.

11:48

Uh, this particular image doesn't show the other renal

11:50

vein, but you want to make sure that you have some comparison.

11:53

On the sagittal image, you can also see

11:55

that there is renal vein enlargement here.

11:58

One of the things that you'll normally see after

12:00

a few hours, at least, is that the, the kidney

12:02

that's affected, in this case, the left one, will get

12:05

larger and will have a delayed nephrogram phase.

12:09

So those are other things to look at.

12:11

But in this particular case, you know, you

12:12

can see the enhancement is fairly homogeneous,

12:14

and there's just this renal vein thrombus.

12:17

Um, it's important to, to make sure that

12:19

you're not missing a small mass somewhere.

12:22

But generally speaking, uh, this can be a

12:25

benign condition, so just be aware of that.

12:28

And this is just a magnetic view of that.

12:33

Here's a 40-year-old who had sudden, uh,

12:36

flank pain, and they had a fever, so they

12:38

were IV drug users in this particular case.

12:40

But theoretically, people can develop pyelonephritis from

12:44

urinary reflux, uh, and UTI and other causes.

12:49

So generally speaking, imaging is not supposed

12:52

to be, you know, the gold standard for diagnosing

12:55

this, and it should be clinical with urinalysis.

12:57

However, you know, there are patients who

12:58

do not present with the typical symptoms,

13:00

and we do end up finding these incidentally.

13:03

So you can see that this right kidney, where

13:05

I've put the arrows, there's loss of the corticomedullary

13:08

differentiation compared to the left

13:10

side, and the kidney is often a little bit larger,

13:13

because of the inflammation, and often

13:15

you'll see some stranding around it.

13:16

Although in this particular case, I don't see any other.

13:19

Things you can look for is thickening of the urothelium,

13:22

because they can often have a pyelitis associated with that.

13:30

One of the pitfalls on ultrasound, in particular, is that

13:33

if you see an echogenic lesion in the kidney, it's not

13:36

always angiomyolipoma, which is what we typically look for.

13:40

In this case, we have a focal pyelonephritis. In this

13:43

particular patient, if you did additional imaging

13:46

with CT or MRI, which ideally you would not be doing

13:49

an MRI in focal pyelonephritis, but let's say you

13:52

did a CT, you would see that there's no fat here, and

13:55

typically the patients do have pain there and fever.

14:00

So let's move on now to some of the benign lesions.

14:04

So I'll talk about oncocytoma first and then AML,

14:06

and then we'll move on to some of the others.

14:11

So oncocytomas are.

14:13

Benign, and they arise from the intercalated

14:15

cells of the renal collecting ducts.

14:18

They can have a characteristic spoke-wheel

14:21

enhancement pattern, but that doesn't always happen.

14:24

You know, maybe in this particular case we see some

14:26

spokes, but this is not a spoke, and there seems to be

14:29

some sort of necrosis or fluid in the center of this.

14:32

So, you know, they don't always fit the pattern.

14:35

Biopsy is still often performed in these

14:38

patients, and they will stain positive

14:40

for CD117, or KIT.

14:44

Um, but this type of staining also occurs in

14:46

chromophobe RCCs. Our pathology department

14:50

colleagues, our pathologists, are becoming more

14:52

and more adept at making the differentiation.

14:55

However, they do appreciate having that radiology-

14:58

pathology correlation in order to be able to

15:00

be more certain with their final diagnosis.

15:04

So in the past, they all had to be surgically resected.

15:07

But there are other features which

15:09

are currently in the literature.

15:11

Uh, we don't use this at my institution, but I did look up

15:14

to see what other options we had for these types of lesions.

15:18

So there was a paper study, uh, published by Dr. Amin

15:21

and colleagues in 2018, where they looked at the, uh,

15:25

cortex peak-to-early phase enhancement ratio of a nodule.

15:30

So.

15:32

Um, you know, they were able to do ratios of how the time

15:35

curve changes in oncocytoma versus chromophobe RCCs.

15:40

And then there was another paper that came out

15:41

last year looking at something called ALAD, which

15:44

is the aorta-to-lesion attenuation difference.

15:48

And this is on multiple-

15:49

phase CT, uh, particularly using the nephrographic phase.

15:53

And you can try and look at how your aorta

15:55

is enhancing compared to the lesion itself.

15:58

And that's supposed to be, uh, help, you know, differentiate

16:01

with the area under the curve for one versus the other.

16:04

And that's the other being chromophobe RCC.

16:08

So, you know, these are still, they've been published.

16:11

They, you can consider using them, but

16:13

they're not necessarily used at all centers.

16:17

Angiomyolipoma is one of the prototypical

16:20

benign liver—uh, sorry—renal masses.

16:24

And, uh, it's a neoplasm of the perivascular

16:26

epithelioid cells, which are, um, considered benign.

16:31

So the name of angiomyolipoma pretty much says it all.

16:35

Uh, I just wanted to check one thing to tell you that

16:37

I looked up on the perivascular epithelial cells.

16:42

Hang on one second.

16:42

I just want to, because I'm not a pathologist.

16:45

But let's just see what they—

16:49

So those are modified smooth muscle cells.

16:52

So just, uh, when the pathologist looks

16:54

at it, that's what they're looking for.

16:56

But AML, angiomyolipoma, that name says it all.

17:00

However, the ratio of the angio component, the

17:03

vascular component versus the fat versus the muscle

17:06

component may vary from one to the other.

17:10

One of the things that's worth looking for when you

17:12

are—when you have made the diagnosis of an AML, so

17:15

you see the fat, you see things, you're comfortable

17:18

with it—uh, but look for aneurysms within the

17:20

lesion because they are prone to form those.

17:22

And even, uh, if they're not particularly large,

17:26

if you do see an aneurysm within an AML, it's worth

17:29

flagging that because typically we've been taught

17:32

that AMLs, um, are usually treated, um, with an—

17:38

by the interventional radiologist to reduce the risk

17:40

of bleeding if they're greater than four centimeters.

17:43

However, if you see an aneurysm within the

17:45

AML, then it's worth flagging that so they can

17:48

potentially consider doing something about it earlier

17:51

so that it doesn't have a high risk of bleeding.

17:55

Now, AMLs with small amounts of fat—

17:57

it can be difficult to differentiate from RCC.

18:00

So that's what we're going to spend

18:01

a bit of time on in this talk.

18:03

So one option is to do very thin-section, uh, non-contrast

18:07

CT, looking for those pixels of fat. Chemical shift

18:12

MRI can be helpful to look for small amounts

18:14

of fat, but there are certain types of RCC

18:17

that can also have small amounts of fat.

18:20

Here is just a potential pitfall where

18:23

we see a fat-containing mass, and—

18:27

the question is, where is it coming from?

18:29

So, uh, I've got a number of images.

18:32

It's the right—

18:33

the right side. We can see that

18:34

there's this fat-containing mass.

18:36

So as we scroll through here, the left

18:39

kidney's normal. We see that it has some

18:41

vascular or soft tissue components within it.

18:44

It is predominantly fat.

18:46

So should we be worried about a

18:47

retroperitoneal liposarcoma?

18:50

Is this a myelolipoma from the adrenal?

18:52

Is it angio—

18:53

myolipoma?

18:54

That's exophytic, coming from the kidney.

18:56

So the key is

18:57

ideally to have as thin cuts as

18:59

possible and then reformatting them.

19:02

So here I've shown you one image where you can see

19:05

that there is, in fact, a small lesion, which when

19:08

you check at, uh, the pixel ROIs, it is, in fact, fat.

19:12

And when you do your reformats on thin-cut

19:15

images, you can actually see that here's that

19:18

fat component I showed you, but there's actually

19:20

a vessel running into the kidney from this.

19:23

So that's the angio component.

19:24

And then most of this was just a

19:26

fat-containing AML that's exophytic.

19:28

So that's the key, is to find where exactly it's coming from.

19:34

So this was exophytic AML. Other things, like I

19:37

mentioned in your differential, would include a

19:40

liposarcoma, and we've seen a couple of cases, which

19:43

I didn't want to show here because they're rare.

19:45

Uh, PEComas extending into the vein.

19:48

Most of the PEComas that I've seen in the literature are

19:51

soft tissue.

19:53

However, we've seen a couple of cases where these

19:55

PEComas, which are kind of in the spectrum of AML,

19:58

but they're at risk for malignant transformation.

20:00

They're mostly fat, and then you can see a long tail of

20:03

fat going into the IVC, and the urologist definitely wanted

20:07

to resect those because of the concern that they could

20:10

have malignant transformation or malignant components.

20:15

We know that AMLs can be associated with

20:17

certain conditions like tuberous sclerosis.

20:19

So if you see somebody who has multiple angio-

20:22

myolipomas, then think about tuberous sclerosis and look for

20:26

additional features associated with that condition.

20:29

So here, on the ultrasound on the left, we've

20:31

got multiple echogenic fat-containing lesions.

20:35

Obviously, based on the ultrasound itself, we can't

20:38

make that diagnosis because we've already seen that

20:40

it could be an infectious process or other things.

20:43

However, on the MRI—sorry—on the CT scan, we can

20:46

see that there's a large fat-containing component.

20:49

We can see that there's a—there's some soft

20:52

tissue components here, so that would be the myo.

20:56

Uh, uh, component.

20:58

And the question is, how many vessels are there in here?

21:01

Is this, you know, actively bleeding

21:03

because this is a very big lesion, and at

21:05

this size it's at high risk for bleeding?

21:07

If you look over here, we can see that there's some

21:10

stranding here in the fat, um, in the left paracolic gutter.

21:13

So the question is, has it bled somehow

21:16

and ended up with peritoneal blood?

21:18

Has it gone below and then back up?

21:20

So they did an angiogram, and they could

21:21

actually see that this person had a large,

21:25

incompletely filling aneurysm,

21:27

which was the site of bleeding.

21:28

So they had to actually embolize that,

21:31

and this was why the patient showed up.

21:32

But on ultrasound, you know, you can put your Doppler

21:35

and look for those, but they can be hard to see,

21:37

especially in a case like this where there's a lot of

21:40

echogenic, uh, material from the fat, from the angio-

21:44

myolipoma.

21:48

Now, minimal-fat AMLs are one of those, uh, lesions which

21:52

we have become better at in imaging to differentiate

21:55

from various renal cell malignant, uh, subtypes.

21:59

But, um, they still can be challenging.

22:02

So 5% of AMLs are found to have insufficient

22:05

fat to be characterized by either CT or

22:07

MRI, and there is that potential overlap.

22:11

So the things to look for—number one—on

22:16

unenhanced CT scan, they're usually homogeneously

22:20

hyperdense to the surrounding parenchyma.

22:22

Maybe not like so dense, like one of those hyperdense

22:26

cysts necessarily, but they're supposed—they're

22:28

supposed to be more dense than the parenchyma.

22:31

On T2-weighted images, like the one I've shown you in the

22:33

top right corner here, it should be of low signal intensity.

22:37

So we can see in the medial aspect of the right kidney,

22:39

there's an area that is homogeneously low signal intensity.

22:43

They typically have low signal intensity

22:46

on the ADC map as well, and they typically

22:48

avidly enhance on the arterial phase.

22:53

So here's just an example of a

22:54

51-year-old woman who had just that.

22:56

So that's the lesion that I showed you on the past slide.

22:59

So on T2-weighted images, it's of homogeneous low

23:02

signal intensity, and on in- and opposed-phase imaging,

23:05

nothing's happening on, uh, pre-contrast

23:10

fat-saturated T1 image.

23:11

There's no actual fat in this that we could

23:13

identify, but post-contrast, we could see that the,

23:18

the lesion itself enhanced peripherally at least

23:21

the same as the cortex of the rest of the kidney.

23:23

So we're sure it's not a dromedary hump because it has

23:26

different imaging characteristics on T2-weighted imaging.

23:28

So it's not something like that.

23:30

It is avidly enhancing, and it does wash out here.

23:33

But the key here is that it's of low

23:34

signal intensity on T2-weighted imaging.

23:37

So this can give you some confidence

23:39

that this is fat-poor AML.

23:43

There's another example.

23:44

So this one was exophytic.

23:46

We can see on the first image, um, that it is

23:49

of low signal intensity on these—well, uh, true

23:53

FISP images, but they're more T2-weighted.

23:56

Here's a more proper T2-weighted

23:58

image with and without fat saturation.

24:00

So, you know, it's a little bit darker

24:03

or similarly dark to the cortex.

24:06

Then on in- and opposed-phase imaging,

24:07

this one was actually dropping in signal.

24:10

It showed avid enhancement with some

24:11

washout, and this was felt confidently to

24:14

represent a, uh, lipid-poor angiomyolipoma.

24:20

Here's a bit of a problem case that we

24:22

recently had. So this was a patient who presented with

24:26

actually liver lesions, and they had a number of lesions

24:29

that had been followed for a while, and they were difficult

24:32

to characterize, and they also had this renal mass.

24:36

So the mass, you know—here's the pre-contrast, uh, CT.

24:41

It's slightly hypo to the parenchyma.

24:43

Certainly not hyper, so that doesn't quite fit.

24:46

It is enhancing on the arterial phase.

24:47

Maybe not like the cortex. It's washing out.

24:51

Washing out on the more, uh, more

24:53

nephrographic and more delayed phase.

24:55

So, you know, it doesn't really fit.

24:57

It hadn't changed in four years, but we know

25:00

that some RCCs can be very aggressive, but

25:02

others can sit and not change much for a

25:05

long period of time before something happens.

25:07

We see that there is some drop in signal on the in-

25:10

and opposed-phase, and maybe, you know, that you

25:12

can actually see there is some fat here, and perhaps

25:15

you can actually imagine that, uh, there is some fat.

25:19

I didn't show you the pre-contrast fat-saturated

25:21

T1-weighted images, but you might imagine

25:23

that there is a speck of fat in there.

25:26

There were no calcifications in it.

25:28

On the CT, on T2-weighted images, there

25:31

is this one area that's a little bit.

25:33

Not homogeneous, but the rest of it is hypo—they call

25:36

it, uh, hypo-intense to the rest of the parenchyma.

25:40

And then, you know, it eventually does wash out.

25:43

Maybe it has a spoke-wheel

25:44

pattern here, but not—not really.

25:47

So this one is a bit tricky,

25:48

but, um, due to the fact that it—

25:51

we felt that there was actually a little bit of fat in it.

25:54

This was probably a fat-poor AML, but it could be that

25:59

this would be a case, if you're not sure—especially

26:01

if you don't have previous—and depending on the

26:03

patient's, uh, condition, they may want to do a biopsy

26:06

just to confirm this.

26:08

Uh, the liver lesions—

26:09

it turns out—were actually, um, sclerosing hemangiomas.

26:14

So they were also a little bit unusual.

26:16

They were causing some capsular retraction, and it

26:18

wasn't clear at the beginning whether these two things

26:20

were related or not, but in the end, they were not.

26:24

So this is just an example of, uh, a lesion

26:27

that can be problematic, but we were

26:29

pretty confident that it was going to be benign.

26:33

As I mentioned before, with that

26:35

exophytic AML that was mostly fatty,

26:39

there are other fat-containing, uh, lesions in

26:42

this area, which can be tricky to differentiate

26:45

if they're coming from the kidney or elsewhere.

26:47

So here we have two patients who have very

26:49

exophytic, predominantly fat-containing masses.

26:52

The one on the right, if you look

26:54

carefully, um, you can see that—

26:57

you know, maybe this is part of the adrenal

26:59

gland, and it's splaying the adrenal gland

27:01

and maybe, therefore, arising from it.

27:03

And then maybe you can actually see that part of

27:05

this adrenal gland here is draining into the IVC.

27:09

So this mass is actually coming from the

27:10

adrenal gland, whereas on this other side,

27:13

you see there's a large fat-containing—

27:15

it's, uh—

27:16

you know, here you kind of wonder if it's a claw sign

27:18

coming from the kidney, but sometimes it's not that easy.

27:21

But in this case, you can actually see the

27:22

vessel that's draining into the kidney.

27:25

So this, on the right, is a renal angiomyolipoma,

27:27

whereas on the left it was an adrenal

27:30

myelolipoma with, um, the draining vein.

27:37

Again, I told you before that not all lesions in

27:40

the kidney, which are echogenic, are, uh, AMLs.

27:44

So this is just another pitfall.

27:46

Uh, we also saw examples where it could be an infection,

27:50

and in this case, it's quite well circumscribed.

27:54

The patient was not sick.

27:56

So the question is, is this an angiomyolipoma?

27:58

It was an incidental finding.

28:00

Well, here's the non-contrast CT,

28:02

and here's the nephrographic phase.

28:04

Uh, it's not hyperdense here, so it's probably not

28:08

angiomyolipoma, and there's definitely no fat in it.

28:10

So this ended up having to have a biopsy.

28:13

It went from 35 Hounsfield units per pre-contrast to 95.

28:17

Actually, that was actually, uh, 55, so I apologize.

28:20

That's an error.

28:21

So that, uh, did enhance, but not massively.

28:24

And this was actually an RCC,

28:27

rather than a lipoma, as may have been

28:30

considered on the original ultrasound, but

28:33

was confirmed not to be that on the CT scan.

28:36

So not all echogenic lesions on ultrasound are benign.

28:40

They could be infectious, and they

28:41

could be a different malignant tumor.

28:44

And it's just like in the liver when we see

28:46

something echogenic, well circumscribed, we think

28:48

of hemangiomas, but it's not always the case.

28:50

And it again depends on the patient's age

28:53

and their pretest probability in the case

28:54

of hemangiomas as to what we do next.

28:58

So if you have a—if you've worked up the

29:01

case and you're still not sure what it is,

29:02

they may require either resection or a biopsy.

29:07

Okay, here is—uh—so I said we're going to work through some

29:09

of the benign lesions and have a way of working them up.

29:13

And now we're going to show you—I’ll show you—a few

29:15

benign but, uh, less common lesions, and then I'll

29:19

show you some less common malignant lesions as well.

29:22

So the first one is minimal—

29:26

uh, these ones are called AMLEC,

29:28

which is an AML with epithelial cysts.

29:30

The one that I'm showing you here in the top right

29:32

corner, there's the cystic component—that's the

29:34

white arrow—and the black arrow is showing the solid.

29:37

In this case, it was—

29:39

just two parts to it.

29:40

Perhaps a little bit more complex above or below.

29:42

But, you know, this one has a large soft tissue component.

29:46

Um, but it is a benign variant, a cystic

29:48

variant of an AML, and CT or MRIR.

29:53

You should consider that in the differential

29:54

diagnosis of an adult who has a cystic

29:57

neoplasm of some sort, but other

29:59

things to consider include cystic RCCs.

30:02

Cystic nephroma or multilocular cystic

30:04

nephroma and mixed epithelial stromal tumors.

30:07

So you can't always tell the difference.

30:10

If they have fat in them, great, but they don't always.

30:13

And the imaging for AMLEC is often not specific,

30:16

and biopsy is required with immunohistochemistry.

30:19

However, uh, they do have some distinct features, um,

30:23

which is helpful, and they are reactive to melanocytic

30:27

markers, and they're also ER- and PR-positive.

30:30

So the pathologist, you know, if you're at all considering

30:33

that diagnosis, put it in your differential so that the

30:35

pathologist can consider using these types of stains.

30:39

So here's that 41-year-old woman

30:41

with a final diagnosis of AMLEC.

30:43

So pre-contrast, it's somewhat exophytic; maybe it's a

30:46

little bit hyperdense to the cortex on pre-contrast, maybe.

30:50

There's definitely a cystic component and a

30:52

solid component, but there's really no fat.

30:54

Here's another cystic component, solid component on the

30:56

coronals, and there's a large, uh, soft tissue component.

31:00

So on the low-power field here, here's the cystic

31:03

space.

31:04

And basically, there was no fat seen anywhere.

31:08

And when you do the magnification views, there

31:10

were actually a lot of vascular channels.

31:12

So that goes along with an AML, the, um, uh,

31:13

angio component.

31:16

And when they looked at the cells here—so this

31:18

is the cystic part here, this is the lining here—

31:21

um, not only do they see a lot of vessels here, but when

31:24

they do look at the nuclei, they're neither enlarged

31:26

nor showing an abnormal mitotic pattern.

31:29

So those are all

31:30

features that are helpful for the pathologist

31:32

to make the diagnosis of a benign condition.

31:37

Another type of AML is the epithelioid AML.

31:40

So these ones are, uh, mesenchymal neoplasms,

31:43

and they do belong to the PEComa family.

31:46

And as soon as you start talking about the

31:47

PEComa family, then they often have malignant

31:50

transformation risk, and they're usually resected.

31:54

The, um, imaging of epithelioid AML is usually more

31:59

aggressive-looking, like these ones that I'm just

32:01

showing you. They can look

32:03

like a sarcomatoid RCC or some sort of high-grade RCC.

32:07

So prospective diagnosis is often challenging.

32:11

Um, they did a review of, uh, a bunch of these

32:15

epithelioid AMLs back in 2012, and

32:18

they published their results.

32:19

They found that most of them were very

32:21

large, in the range of 14 centimeters.

32:24

They were incidentally found initially, although some of

32:26

them presented with some flank pain due to their size.

32:29

They're usually well, uh, well circumscribed.

32:32

Uh, they may have some lobulated contours, but

32:34

not microlobulation, and because of their size, they

32:37

will extend beyond the cortex of the kidney.

32:40

There's usually rapid wash-in, slow

32:42

washout, and heterogeneous enhancement.

32:45

And then the growth patterns of these, uh,

32:47

epithelioid AMLs can show an invasive pattern,

32:50

including degeneration, necrosis, and hemorrhage.

32:53

So these are things that we don't normally see with AMLs.

32:56

Necrosis and hemorrhage.

32:57

Well, hemorrhage you can, yes, but necrosis not so much.

33:01

So, uh, if you see something like this, you're going to

33:04

end up having to either resect it or biopsy it.

33:08

Other ones, uh, metanephric adenomas and hemangiocytomas—

33:11

I'm not going to show you all lipomas

33:13

because, A, they're very rare, but, B,

33:15

they're just a blob of fat.

33:18

So metanephric adenoma—we start with ultrasound again.

33:21

We see two different images, and they look echogenic.

33:25

So we know that we have a differential

33:28

now for echogenic lesions.

33:29

And when we did the MRI, we could see that, uh, it's

33:33

homogeneous to the cortex on these T2-weighted

33:35

images, certainly not hyper—um—hyperintense on

33:39

the T2-weighted images.

33:42

It didn't have any fat in it.

33:44

And, you know, basically there's no specific

33:46

imaging characteristic that you can make

33:48

necessarily to come up with this diagnosis.

33:51

So it's pretty uncommon, but it's benign.

33:53

And it's composed of these primitive, uh,

33:55

small primitive cells or small blue cells, and

33:58

they can look like immature metanephric tubules.

34:01

Very wide range of, uh, presentation in terms of age.

34:05

And, uh, usually they're incidental, but some present with

34:09

hematuria or an abdominal mass, depending on their size.

34:12

Again, these are ones that you'll either

34:13

have to biopsy or resect, for the most part.

34:16

Hemangiocytoma is a term that used to be used all

34:20

over the place, but most of the time when somebody

34:22

has something like that in the brain or, uh,

34:24

MSK, they now call them solitary fibrous tumors.

34:28

So I've still seen them called this in

34:30

the kidney, but, uh, this may be changing.

34:33

So again, there's no way you can say that this is benign

34:37

just looking at this CT image.

34:39

So—

34:41

they either end up resecting them or

34:43

biopsy, but usually, you know, something

34:45

like this would go straight to resection.

34:47

They do have a propensity for younger patients, but again,

34:51

I don't think you can slam dunk this, uh, prospectively.

34:56

Um, yeah, they can present with hypertension as well.

35:02

Okay, so we've talked about a bunch of

35:05

benign lesions, and now we will cover

35:08

some of the malignant lesions, so RCC being

35:11

the most common one that we talk about.

35:13

And we know that there are several subtypes of RCC,

35:16

and now, with imaging, with the work of, uh, many

35:20

pioneers in imaging—Stu Silverman, for

35:22

example, and many others—they have been able

35:25

to identify ways that we can use imaging to subtype

35:28

these prospectively because we know that certain

35:30

types of RCC have a worse prognosis than others.

35:33

I'll show you a couple examples of TCC, lymphoma, and, of

35:35

course, metastases can happen in the kidney, although

35:38

they're not the most common location. Still, I've seen,

35:41

you know, a number of metastases, including, um, melanoma.

35:45

I've seen breast cancer, lung cancer in particular.

35:49

So, you know, just because you see a liver—

35:51

sorry, a renal mass—doesn't mean you don't

35:53

have some other malignancy to consider.

35:56

So here I have a summary table, which I will

35:59

show again at the end if you want to remember

36:01

anything that I say or take a picture of anything.

36:03

This is the one. So this is, uh, my way to remember how

36:07

to differentiate the different kinds of RCCs, and also

36:11

I threw in fat-poor, or lipid-poor, AML. So we already

36:15

talked about AML, so it's usually hyperattenuating on

36:18

CT and low signal intensity on T2-weighted images.

36:21

If you look at papillary RCC, which is the second most

36:24

common type of RCC, it is also hyperattenuating on CT

36:27

and of low signal intensity on T2-weighted images.

36:30

But this is where they—

36:32

um, this is actually not where they change.

36:34

They can also drop in signal on in-

36:36

and opposed-phase imaging, potentially.

36:38

However, the enhancement of fat-poor AML is to be

36:43

avidly enhancing and then they wash out, whereas

36:46

papillary RCCs typically slowly and gradually enhance.

36:49

So you need the post-contrast images to

36:52

help you make that distinction because, uh,

36:54

some of the other features are very similar.

36:57

Now, in terms of enhancement, we can see that

37:00

there's an overlap between clear cell AML—

37:03

uh, sorry—clear cell RCC and lipid-poor AML. So

37:06

they both avidly enhance with washout. However,

37:10

they differ because the malignant ones are

37:12

typically of high signal intensity on T2,

37:15

and they're iso- or hypoattenuating on CT.

37:19

So this will help you, pre-contrast,

37:22

to differentiate those two types.

37:24

And then we also have chromophobe RCC, typically iso-

37:27

attenuating, uh, on CT, but they can have fat with calcium.

37:32

So if you see calcium in a renal mass, don't

37:35

think of an AML because that's usually, um—

37:39

not a good sign.

37:41

And it's because they have osteoblastic change.

37:45

They usually have intermediate signal on T2.

37:47

They don't change.

37:48

There's no fat in them, uh, on in- and opposed-

37:50

phase imaging, and they do not avidly enhance.

37:53

So hopefully you will be able to not fall into the trap if

37:57

you see a thing of fat, but it's, uh, outlined in calcium.

38:01

Don't think of an AML. Think about chromophobe RCC.

38:06

Anyway, I'll show examples of this, and then we'll

38:07

just recap, at the end, that particular slide,

38:09

because I really like that slide.

38:11

It always helps me when I'm trying to look at these masses.

38:15

So RCCs arise from proximal convoluted tubules.

38:18

They're usually large, uniform cells.

38:21

Um, and they have clear cytoplasm now.

38:24

They can have high signal intensity on T2-

38:26

weighted images, as we would expect with

38:28

large cells that have a lot of cytoplasm.

38:30

But we know that papillary RCCs don't do that.

38:33

Most of them arise spontaneously, but they

38:35

have been shown to be associated with smoking.

38:37

Even though smoking is much more associated

38:39

with transitional cell carcinoma.

38:41

They've also been potentially associated with increased

38:44

BMI and hypertension, uh, diabetes, and trichloroethylene

38:49

exposure, but these are not as well, uh, established. So,

38:52

grain of salt for now.

38:55

Twenty-five percent of them, uh, develop a paraneoplastic

38:59

syndrome and can have—um, sorry—can develop paraneoplastic

39:02

syndromes, including hypercalcemia, hypertension,

39:06

polycythemia, or even limbic encephalitis.

39:10

So often, when we think of limbic encephalitis and

39:12

malignancy, we're thinking about breast cancer and

39:14

things like that, but, uh, RCCs can do that as well.

39:18

And then there's this rare condition called

39:20

Stauffer syndrome, which is a paraneoplastic

39:22

syndrome related to RCC, where they get hepatic

39:25

dysfunction, but there's no actual mets in the liver.

39:28

They just have hepatic dysfunction.

39:30

So just, uh,

39:31

note in case you ever see that on a multiple-choice exam.

39:35

So here's just an example on

39:37

ultrasound of a clear cell RCC.

39:39

This one actually seems to have some cystic changes.

39:42

Um, it's the most common—that is, clear

39:44

cell is the most common subtype of RCC.

39:46

They are usually avidly enhancing.

39:49

Uh, and then—

39:52

they may show intracellular lipid, but these tumors

39:55

are often quite heterogeneous, and they usually

39:57

have some areas of high signal intensity on T2-

40:00

weighted images, like I showed you on that table.

40:07

Here is, unfortunately, a, uh, more advanced

40:09

clear cell RCC, so always look for that

40:11

renal vein thrombus, or tumor thrombus,

40:13

more importantly.

40:15

And if you do see tumor thrombus,

40:17

obviously that puts it into a higher

40:19

category when you, uh, give it a stage.

40:22

And when you see IVC thrombus, look up to see if

40:25

it's going into the heart, because if they are

40:27

planning to operate, once it goes toward the

40:30

diaphragm, then they have to involve other surgeons.

40:33

Uh, to make sure that not only the vascular

40:35

surgeon is involved from below, but they

40:37

may need the cardiac surgeon as well.

40:40

And usually, one other thing—

40:41

by the time they get this big, it's very

40:43

important to look for metastases elsewhere,

40:45

because you know they can metastasize.

40:47

So popular places that are missed, that

40:49

I've noticed, are in the soft tissues.

40:51

These are not metastases over here.

40:53

These are actually vessels that have

40:54

been sort of parasitized, because this

40:55

obviously needs a lot of blood flow.

40:58

So it has used vessels from the

41:00

SOAs, but look in the subcutaneous

41:03

tissues, but also in the muscles, for potential metastases.

41:08

Uh, here's just an example of another

41:09

patient who has an echogenic renal lesion.

41:12

Now this one isn't quite as echogenic, and it's

41:13

maybe a little bit ill-defined, but still, on T2-

41:16

weighted images, it has high signal intensity.

41:18

And post-contrast, it has an area that's enhancing, although

41:21

not all of it, and the periphery is enhancing because

41:24

we know that the lesion goes all the way to the cortex.

41:26

So the cortex, or the outside portion of

41:29

this—not the cortex, but the outside

41:30

portion of this lesion—is enhancing avidly.

41:33

This one actually ended up being a tubulocystic

41:35

carcinoma, which is yet another subtype of malignancy.

41:41

Papillary RCCs are the second most common

41:43

subtype of RCC, and they account for 15 to 20%.

41:47

Um, these are, uh, usually seen more commonly in

41:51

patients who are on long-term dialysis and in those who

41:54

have hereditary papillary renal cell carcinoma gene.

41:58

Uh, so they're usually hyperattenuating on non-contrast CT.

42:02

So this is one area that we have to make

42:03

sure we don't mix up with the lipid-poor

42:05

AML.

42:06

They also have low signal intensity on T2-

42:08

weighted images, like lipid-poor AML, but unlike

42:11

the cystic, uh, sorry, uh, the clear cell RCCs.

42:16

And they typically, unlike AML, show

42:19

gradual, slow, progressive enhancement.

42:22

So that's very important to look for that.

42:23

So you need multiphase post-contrast imaging to

42:26

really tell. These ones are typically associated with

42:29

lower histologic grade and less risk for metastases.

42:33

So papillary RCCs are associated

42:35

with better overall survival.

42:37

So if you can tell them that in advance, uh, then you

42:40

know it may change the patient's treatment and prognosis.

42:46

So here's just an example of another patient

42:48

who has an echogenic lesion in the kidney,

42:50

not an AML in this case, because I'm showing

42:52

you where my arrows are—there's no fat in it.

42:55

It is, uh, somewhat enhancing, but it's pretty slow

43:00

enhancement, and it never really enhances a lot.

43:06

So there are actually two subtypes of papillary RCC,

43:08

but I'm not gonna go into that, uh, in this, uh, talk.

43:12

But they can enhance very

43:15

minimally.

43:16

And that's something that's a little bit scary, because

43:18

one of the things we rely on when we're looking for

43:21

a cyst—differentiating cyst from solid—is to see

43:23

that there's no change between non-contrast, arterial,

43:26

nephrographic, delayed, and, you know, occasionally

43:30

they can enhance less than 10 Hounsfield units.

43:32

So I'm not telling you to panic and call RCC

43:35

for every cyst that you see, but just be aware.

43:38

Uh, mean enhancement is usually in the

43:40

range of 35 to 45 Hounsfield units

43:42

between pre-contrast and more delayed images.

43:45

But like I said, sometimes it

43:47

can be very minimal enhancement.

43:49

So having thin cuts is helpful because you might see

43:52

a parenchyma or some sort of, um, architecture inside

43:57

that will help you see that this is, in fact, not a cyst.

43:59

MRI is usually helpful for that, too.

44:02

And, uh, MRI with subtraction imaging is also

44:04

helpful if the CT is equivocal in terms of

44:06

how much you're actually seeing enhancing.

44:12

Uh, just be aware that even if it's a

44:14

papillary, uh, they can metastasize.

44:16

So here they resected this, and a few months

44:18

later the patient had metastasis in the

44:20

renal bed and also in the left psoas muscle.

44:23

So, uh, just a risk to be aware of, and these

44:26

patients are often followed long-term with imaging.

44:31

All right, so we did, uh, um,

44:36

the other types of RCC, and now we've got clear cell.

44:39

So here is a clear cell that can mimic—oh, I'm sorry.

44:44

You know what?

44:44

This should have been earlier.

44:45

Let's just forget this case.

44:46

It's just redundant.

44:49

But this is just showing, uh, an

44:51

example here of it’s clear cell.

44:55

Okay, chromophobe—that's what I really wanted to get to.

44:57

So here's a chromophobe RCC in a 64-year-old woman.

45:01

So on T2-weighted images, uh, it's a

45:03

bit bright, so it's definitely not dark.

45:06

On pre-contrast, it is darker than the cortex,

45:10

so of lower signal intensity. On the arterial

45:12

phase, it's not really enhancing very much.

45:15

Overall, there's this one component here, perhaps,

45:18

and then, you know, it's just not enhancing

45:19

very much on the more delayed images, too.

45:21

Again, maybe there's that central thing, but that's,

45:24

uh, that's what we're seeing in this chromophobe RCC.

45:29

Again, biopsy may be required in some of these examples,

45:32

but it just gives you some idea of what to look for.

45:36

Here is a 65-year-old who ended up having chromophobe RCC,

45:41

and they actually had some osseous metaplasia, so this was

45:44

actually an exophytic one, which was kind of interesting.

45:47

This is the lesion here.

45:48

So, A, you have to figure out that it's coming

45:50

from the kidney and not from somewhere else.

45:52

And when you look at it carefully, you

45:53

can actually see that there is fat here.

45:55

And when you magged it up, it was definitely

45:57

fat pixels showed negative; however,

46:00

they also had this focus of calcium here, and most of

46:03

them, they actually had additional, uh, similar droplets

46:07

of fat, but they had some, uh, peripheral calcification.

46:10

So when you see these foci of calcification here,

46:13

or a rim of calcification, more importantly, in

46:16

something that has fat, do not consider an AML anymore.

46:19

You should definitely be thinking about chromophobe RCC.

46:23

This one just happened to be

46:24

unusual because it was exophytic.

46:27

All right.

46:28

TCC is most often associated with smokers. They have a

46:31

field effect because they have been smoking, and it affects

46:34

the kidneys and bladder, all lungs, everything else, but

46:37

so it is the second most common kind of bladder cancer.

46:40

Uh, the most common bladder cancer.

46:41

Second most common kidney. You can see them

46:43

at the same time if you diagnose bladder.

46:45

So they can be synchronous, or they

46:47

can be metachronous at another time.

46:50

So it is important to be aware of those, and they

46:52

do not typically enhance as avidly as renal cell

46:55

carcinomas, particularly not the clear cell.

46:58

And they can also occur in patients who have been exposed

47:00

to various types of chemicals, aniline dyes in particular.

47:05

So here is just an example of a

47:06

woman who has a TCC on the right.

47:09

So this is T2.

47:10

You can see she has some parapelvic cysts, but here

47:12

there is some soft tissue filling this renal pelvis.

47:16

There is restricted diffusion on ADC, and

47:19

there is some enhancement, but it is certainly not

47:21

avid, but it is following the collecting system.

47:24

So this is a TCC.

47:27

Here is just an example of moving on again.

47:30

Uh, renal lymphoma.

47:31

Renal lymphoma is tricky because

47:33

it can have various appearances.

47:35

So the first one I have shown you on the bottom

47:38

left, you have diffuse enlargement of the

47:40

kidneys with replacement of the parenchyma.

47:43

The next one is actually perirenal, so the kidney

47:46

itself does not look too bad, and you can actually

47:48

see the artery—not on this image—and the vein.

47:50

Perfectly fine.

47:52

Uh, but there is this rind of tissue. You might want to

47:55

think about other diagnoses, like IgG4, for example.

47:58

But lymphoma on diffusion-weighted imaging shows

48:00

significant high signal intensity on high b-values

48:03

and restricted diffusion, unlike other diagnoses.

48:07

And here is just an actual mass, also lymphoma,

48:11

so they can have variable appearances.

48:14

Another person.

48:14

This one, you know, I do not think I would have

48:16

necessarily been able to make this diagnosis a

48:18

priority because this one was actually affecting

48:21

the renal vein, so this is very unusual.

48:23

They did have a bunch of lymph nodes, but, you know,

48:25

if you have a patient with TCC, this can look very

48:28

similar, and they can also have metastatic lymph nodes.

48:31

This person did not even have splenomegaly, so there

48:33

will be cases where, you know, it is really not

48:36

clear-cut, and you will need to do, uh, biopsies.

48:39

Here is just another example of renal lymphoma.

48:41

This one was replacing a lot of the right kidney.

48:44

And you can see on diffusion-weighted images on

48:46

the ADC map that it is very low signal intensity.

48:50

And then after they treat it, that tissue, uh, from the

48:53

lymphoma goes away, and you end up with atrophy of the kidney.

48:58

But they can definitely respond very well to the therapy

49:00

for lymphoma as long as they know that is what it is.

49:04

So there are a lot of syndromes that

49:05

can be associated with renal masses.

49:06

I will not go through all of them, but, you know, we have seen

49:09

von Hippel–Lindau in our careers.

49:12

Birt–Hogg–Dubé, I will show you.

49:14

Uh, tuberous sclerosis is usually AMLs,

49:17

but they can also have clear cell RCCs,

49:20

and, of course, von Hippel–Lindau is clear

49:22

cell RCC.

49:25

So here is just an example of two patients.

49:27

Uh, interesting case.

49:28

They have a mass; it kind of looks like the

49:30

lymphoma I just showed you, and there is a bunch

49:32

of soft tissue in the retroperitoneum here.

49:34

This one has some retroperitoneal soft

49:36

tissue, but there is definitely a mass.

49:37

However, um, post-contrast, uh, lower down, this person

49:42

has a lot more soft tissue, uh, whereas the other person

49:45

has another lesion here, and they also have liver masses.

49:51

So in this particular case, we

49:52

had a renal mass plus other masses.

49:54

You might think about RCC with mets,

49:55

but they did not look quite right.

49:57

You might think of mets from another primary

49:59

altogether—lung or melanoma—maybe lymphoma.

50:02

But in these patients, they both had sickle cell

50:04

trait, and these patients actually both had

50:11

medullary RCC, so they can have an infiltrative

50:14

appearance, but if you know they have sickle cell trait,

50:16

consider somebody with a renal mass as having medullary

50:19

RCC.

50:22

Here's just the patient with

50:23

multiple bilateral clear cell RCCs.

50:26

So when you see that, think about von Hippel–Lindau,

50:28

or some other, you know, familial problem. They had

50:31

had RFA here, so this is of low signal intensity here.

50:34

She also happens to have a cyst here,

50:37

but this one kind of looks like a cyst.

50:38

But if you look carefully, there's something there,

50:40

and post-contrast, you can actually see as we go down.

50:43

That's the post-RFA area here.

50:45

Here, this one's a cyst, and this

50:47

one is not because it's enhancing.

50:49

So even though on T2 it can be hard to

50:50

differentiate, you can clearly see the difference

50:52

between a cyst and a clear cell RCC here.

50:56

And there's multiple of them.

50:58

And this is again the coronal.

51:00

We have multiple clear cell RCCs in this patient.

51:05

This is just an example of a patient with Birt–Hogg–Dubé.

51:09

So they have a triad of, uh,

51:11

deletion mutation on chromosome 17.

51:13

They present with follicular fibro-

51:15

folliculomas of the face and trunk.

51:17

They have renal cell, uh, lesions, which can be chromophobe

51:21

RCC or some sort of hybrid oncocytoma and chromophobe RCC.

51:26

And they also present with cysts in the lungs.

51:30

So just to be aware of that.

51:33

So here they have the kidney and the lung.

51:39

When you're working up an RCC or a mass, uh, depending

51:42

if you have contrast or no contrast, there are

51:46

algorithms, which are easily, uh, obtainable from the ACR.

51:49

So this one was published in 2017.

51:51

So if you have a non-contrast CT, incidental,

51:54

uh, renal mass, if it's too small to

51:56

characterize, then, uh, you're stuck.

52:00

You know, you may have to do

52:01

additional workup if it's homogeneous.

52:04

If there's, uh, very little enhancement,

52:06

then it's probably a cyst.

52:08

If there's significant, uh, density on this, then it's

52:12

probably a hemorrhagic cyst or proteinaceous cyst.

52:15

But when the density pre-contrast—sorry about that—

52:17

non-contrast.

52:18

When the density is indeterminate, then you

52:20

may have to move on to additional imaging to

52:22

really see what's actually happening in there.

52:25

So, because we know that, uh, renal cell carcinomas can

52:28

have, uh, slightly reduced density compared to the cortex.

52:32

If it's homogeneous, uh, and you can see mural

52:36

nodules, septations, and calcifications, then

52:38

again, you're stuck in the indeterminate category.

52:40

So you have to do additional imaging.

52:44

If you have an incidental renal

52:45

mass on a contrast-enhanced CT.

52:47

There's also an algorithm that you can follow.

52:50

Again, we have things that are less than a centimeter.

52:52

You may still be stuck having to do additional imaging

52:54

or follow-up if it's homogeneous on the post-contrast.

52:58

Uh, and it's not really enhancing much.

53:01

Then you're fine.

53:02

If it's enhancing more, then you start

53:04

having some, um, potential for malignancy.

53:08

Now, before it used to be more than 20 Hounsfield units.

53:10

There seems to be more and more research now

53:12

thinking that, you know, you can probably

53:14

push that up to at least 30 Hounsfield units.

53:17

But again, um, you should have multiphase

53:20

imaging and ideally have an MRI to make sure

53:22

that you're not missing something malignant.

53:26

And then if it has fat, well, I told

53:28

you if it's obviously fat, great.

53:30

If it's large, then you may want to

53:32

go manage it for risk of bleeding.

53:35

But if it has calcification and fat, then we

53:38

definitely have to worry about chromophobe RCC.

53:42

So my final summary table that I showed you earlier.

53:46

Again, if you didn't get a chance

53:47

to copy that, here it is.

53:49

So fat-poor AML is benign.

53:52

These ones are not fat-poor AML.

53:53

And papillary RCC have similar imaging, uh,

53:57

appearances on pre-contrast images, but they differ

53:59

significantly post-contrast, whereas clear cell

54:02

RCC enhances similarly to fat-poor AML, but has

54:05

imaging characteristics that differ on pre-contrast

54:09

images, and chromophobe is not as

54:12

common, um, but can have fat and calcium.

54:14

And these are, they do look

54:16

different from all the other ones.

54:19

So, uh, final pearls, that true enhancement versus pseudo-

54:22

enhancement is important to identify and differentiate.

54:25

So subtraction imaging can help if you have

54:28

enhancement of, um, a lesion that's indeterminate,

54:31

you may end up having to do a biopsy.

54:33

These days, it can actually be a little bit more.

54:36

Renal masses that are less than four centimeters are more

54:39

likely to be benign, but don't hang your hat on this.

54:42

But they're also much less likely to metastasize at that point.

54:47

And lipid-poor AML cannot always be differentiated from RCC on

54:50

imaging, but there are a lot of imaging, uh, characteristics

54:53

that I've shown you, which will help you along your way.

54:57

All right, so that's it.

54:59

We just have a couple of minutes.

55:02

For questions.

55:04

I do see some questions in that Q and A feature.

55:07

Yeah.

55:07

So somebody asked, what about multilobulated, more

55:10

than three septa cystic lesions, uh, to excise?

55:14

Well, again, I would recommend

55:15

that you look through the Bosniak.

55:18

So somebody asked a question about multilobulated, more

55:19

than three septa in cystic lesions.

55:23

So, you know, the Bosniak 2019

55:26

characteristics, um, are very helpful.

55:28

To follow that, uh, and they may help you.

55:31

So they look at number of septations, but also

55:33

the thickness and the degree of enhancement.

55:35

So I would suggest that you look at the Bosniak 2019

55:38

version that might help you to be more confident

55:41

in your ability to not have to excise everything.

55:45

Uh, and the next question was what MRI difference

55:47

between minimal fat-containing AML and RCC.

55:51

So I hope that you've seen on my table those two

55:54

differences, so you can go and copy that, uh, table.

55:58

But basically the enhancement, um, varies depending on

56:03

certain types and the pre-contrast imaging that varies.

56:07

When is renal biopsy indicated and not surgery?

56:10

So the risk of seeding, you know, used to

56:12

be a big concern, but more and more it's

56:15

not been shown to be as big of a problem.

56:17

And so it really depends.

56:19

I mean, they should be discussed at

56:21

multidisciplinary case conference, and it

56:22

may depend on the patient's characteristics.

56:25

So if they're very healthy and they just want it,

56:27

they can just go straight to surgery.

56:29

If there are comorbidities and they want to

56:31

see if it's actually benign and don't have

56:33

to operate, then they may go to biopsy.

56:36

So, um, you know, that would differentiate.

56:40

That's one reason to biopsy versus not biopsy.

56:43

And should AMLs be biopsied?

56:45

Well, a typical AML should not be biopsied.

56:48

If it's big, then you may want to refer them

56:51

to interventional radiology, particularly

56:53

if they have a lot of vascular components.

56:55

But otherwise, they don't really need much.

56:57

And we may follow them from time to time just to

57:00

make sure they're not growing, because some stop at,

57:03

you know, two some years, but some become very, very large.

57:06

And there you are.

57:07

What is the meaning of hyperattenuation on CT?

57:10

So if you look at a, I'm talking about non-contrast CT.

57:14

So if you look at the outline of the kidney and you look at

57:17

the cortex of the kidney, uh, and you look at the density

57:21

of that, and then you look at the density of the lesion.

57:23

If the density of the lesion is more than the

57:26

background kidney, that's considered hyperattenuating.

57:28

So it's got a higher Hounsfield

57:29

unit than the background kidney.

57:33

What is PEComa family?

57:34

Well, yeah, uh, those are, uh, they're a type of tumors,

57:40

um, that I, you know, I'm not an expert on that.

57:43

I will have to ignore that question, not

57:46

because I don't wanna answer, but, um,

57:48

they are at risk for developing malignancy.

57:51

I've seen a few that are almost all fat,

57:54

but most of them are very solid, and, and,

57:57

it's all the components, and you wouldn't necessarily

57:59

be able to know what it is before you do a biopsy.

58:01

But they do have malignant transformation.

58:03

I just can't tell you from the pathology

58:04

perspective, 'cause I don't know enough about them.

58:08

All right.

58:09

Uh,

58:11

A little on microlobulation and lobulation.

58:14

See, we have like one minute left, maybe.

58:16

So people can be born with lobulated kidneys.

58:20

Usually in, in the fetal ultrasound you

58:22

can actually see that they are lobulated.

58:24

And as we grow, they sort of smooth out. Some

58:27

people's teeth can have little, you know,

58:29

they look like little beaver, uh, teeth.

58:31

Uh,

58:32

They're irregular.

58:33

Same idea.

58:34

So they're just lobulated outer contour.

58:36

It doesn't mean they have cirrhosis of the kidney

58:38

or anything like that, it's just how they're born.

58:40

Um, and microlobulation versus lobulation.

58:43

Again, it just depends on how small they are, but

58:46

usually they are benign, and you don't have to worry.

58:49

In terms of protocol for renal mass, we usually

58:52

do a non-contrast CT, and then we will do

58:55

an arterial phase and nephrographic phase.

58:57

Some centers also do a delayed phase.

59:00

We typically, uh, it depends on the situation.

59:03

We sometimes do, and we sometimes don't, but if you really

59:05

want to have everything, you do that delayed phase.

59:11

Okay.

59:13

Well, uh, our time is up.

59:14

I don't think I answered every single question, but,

59:17

um, but thank you so much for attending my lecture, and

59:20

uh, you can always contact me through, uh, MRI Online.

59:24

I'd be more, more than happy to answer additional questions.

59:27

Perfect.

59:27

'Cause it brings us to a close.

59:28

I just wanna thank you for your time today, and thanks

59:29

to all of you for participating in this noon conference.

59:32

Reminder that it will be made available on

59:33

demand@mrionline.com, and you can join us tomorrow

59:36

for a talk on Disability Inclusion in Healthcare

59:38

with Dr. Linda Olson and Dr. Peter Palus.

59:40

And other than that, thank you, and have a wonderful day.