0:00

I want to end my discussion of cartilage and

0:04

cartilage-based lesions by showing you a couple

0:07

of classic benign-appearing cartilage tumors.

0:12

This is probably the most

0:13

common that you're going to see.

0:15

We're looking at a frontal and lateral view of

0:18

the knee in an 11-year-old boy with knee pain.

0:23

What can we see?

0:25

We can see, first of all, that

0:26

the physes are still open.

0:28

So that's one of the things I want

0:29

to drive home, is always look to

0:31

see what the physes are doing.

0:32

That's very important in

0:33

the pediatric population.

0:35

Is it very wide?

0:36

Is it about to fuse?

0:37

Has it fused?

0:39

And it's important to include

0:40

that in your dictation.

0:41

It tells the clinician where in the

0:43

maturation process this person is, and it

0:46

may affect the way they provide treatment.

0:48

So, growth plates are widely open.

0:51

And what we notice is this lucent lesion here,

0:54

centered in the epiphysis, may be extending

0:57

down a little bit into the metaphysis.

0:59

So, I want to show you, if I can, with a pen,

1:03

what the margins of this lesion look like.

1:05

Let's do it on the lateral view first,

1:07

because I think it's the most difficult area.

1:10

Here is the top margin, and

1:13

it goes something like this.

1:16

It's going to go through your physis,

1:18

and here, it's a little difficult

1:19

to see, but I think this is good.

1:21

where we're looking at the lesion.

1:23

And I'm not sure what's happening

1:24

at the periphery, so I'm going

1:25

to go from here, like this.

1:28

So I believe the lesion

1:30

looks something like this.

1:31

And of course on the frontal,

1:32

it's a little easier to draw.

1:34

I'm just going to go like this, and it comes up

1:36

all the way up to the surface, comes here, goes

1:40

down like this, and looks something like that.

1:44

That's what I think the lesion looks like.

1:47

Some keywords you want to use, you

1:48

want to say it's relatively well

1:50

marginated in most of what I can see.

1:53

It's centered in the epiphysis with maybe slight

1:56

extension into the metaphysis, and it approaches

2:00

or abuts the chondral or the articular surface.

2:05

And it's eccentric, meaning that it's

2:07

not completely centered; it's slightly

2:09

eccentric towards the medial side.

2:11

So, what the margins are doing is involving

2:15

the growth plate, where it's located.

2:18

And if it abuts the articular surface,

2:20

and is it centered or eccentric?

2:22

So those are the things that you want

2:23

to talk about when you describe a lucent

2:26

lesion in, um, any part of the bone.

2:29

Lateral view, it's a little bit

2:31

more difficult to see, but I think

2:32

you can appreciate it right here.

2:35

It's like this.

2:36

You also want to mention if

2:37

there's any periosteal reaction

2:39

or pathological fractures.

2:41

I don't think this person has it,

2:42

although I'm unsure here at the surface.

2:45

Uh, but.

2:46

I don't think this person has a fracture, but we

2:49

have a well-demarcated, lucent lesion, uh, which

2:53

tells me that it's probably something benign.

2:56

So with that in mind, MR was obtained to

2:59

further characterize what this lesion is.

3:02

We're going to show you a couple of

3:04

MRs, a couple of sequences: first a

3:07

coronal fat-suppressed fluid-sensitive

3:09

sequence, and then a sagittal.

3:13

We have several other sequences: T1,

3:15

post-contrast images available to you

3:17

through your PAC system, but these

3:19

are illustrative of what this lesion is.

3:22

First of all, we see that it's actually

3:24

multiple rounded areas of fluid signal.

3:28

Here, here, here.

3:31

Uh, there's even perhaps a

3:33

little air-fluid level, right?

3:37

So, some people may think, oh, air-fluid

3:39

levels, rounded lucency, aneurysmal bone cyst.

3:43

And you wouldn't be wrong in considering that.

3:46

But other factors have to be considered.

3:49

Its location.

3:51

In the epiphysis mainly, with some, there

3:53

really is some extension into the metaphysis.

3:55

Again, there is no periosteal reaction,

3:58

and there is quite a bit of edema, if you

4:01

look over here in the epiphysis, right?

4:04

So, if you see a well-defined lesion

4:09

in the epiphysis with marrow edema,

4:12

the first three things on your

4:14

differential should be chondroblastoma,

4:17

chondroblastoma, chondroblastoma.

4:19

This is chondroblastoma until proven otherwise.

4:22

Yes, there are some features of aneurysmal

4:24

bone cyst, the fact that you have a couple

4:26

of fluid-fluid levels, and that should be

4:28

on your differential, maybe a little lower,

4:30

but if you see an epiphyseal lesion in a

4:33

skeletally immature person, and it's well

4:37

defined, and there is surrounding edema, it's

4:40

going to be chondroblastoma most of the time.

4:42

This is very, very unlikely to be malignant.

4:46

So, edema, that's the key thing.

4:49

You want to look for edema.

4:50

I have not seen a single case of

4:52

chondroblastoma without surrounding bony edema.