0:01

Thank you, Ashley.

0:02

Hello, everybody.

0:03

This is Gitanjali from Little Rock, Arkansas.

0:06

Um, we're going to see some

0:07

interesting MSK cases today.

0:09

So I'm going to show you some common benign bone

0:13

tumors that often have a classic appearance.

0:17

But I'm going to focus on some

0:19

general concepts that will help you.

0:22

Help us evaluate these cases and will focus

0:25

on key discriminating imaging features

0:27

that will allow us to render a specific

0:29

diagnosis in the majority of these cases.

0:33

It's hard to achieve 100 percent accuracy

0:35

in radiology, but we'll try to be more

0:38

than 90 to 95 percent in these cases.

0:40

So for these cases, I'm going to show you a

0:44

case which will be followed by a question.

0:46

Then we're going to do a quick review of the

0:49

entity, and we'll show you some companion cases

0:51

that will highlight the important features like

0:54

varied manifestations of the same entity, and then

0:56

we do a quick review of treatment at the end.

0:59

So without wasting any time, let's get started.

1:02

But, um, before we look at the cases, some

1:05

general concepts that an imaging of benign

1:08

bone tumors, radiographs are often diagnostic.

1:10

So even the pathologists and physicians are

1:13

looking at you for a specific diagnosis because

1:15

a lot of times, even on pathology, making a

1:18

distinction between a benign and a malignant

1:20

tumor is sometimes hard, and radiographs and

1:25

followed by CT and MR imaging are more diagnostic.

1:28

So some of the general things that we

1:31

need to consider while evaluating these

1:33

cases, um, very similar to brain tumors.

1:36

It's very important to look at the

1:38

age and location for these tumors.

1:40

Once you have the age and location,

1:43

even before you have looked at the lesion,

1:44

you have a short list of differentials with you

1:47

that you need to pick from.

1:49

Once you look at the images, then

1:51

we need to look at the margins.

1:52

Is this lesion?

1:54

Looks aggressive versus non-aggressive.

1:56

Uh, a non-aggressive lesion will typically

1:59

have well-circumscribed margins, whereas an

2:01

aggressive lesion will look more undefined.

2:03

And if the margins are, um, well-circumscribed,

2:05

whether these are sclerotic or non-sclerotic,

2:08

then we need to look at the matrix.

2:09

If it's clear, that means are we looking at a cyst?

2:12

Or does it have a ground-glass matrix, which

2:14

is often suggestive of a fibrous matrix?

2:17

Or does it have any matrix mineralization

2:19

in the form of osteoid or chondroid matrix?

2:22

Again, again, we'll suggest a specific diagnosis.

2:25

The other features to look for, if the lesion

2:27

incites any periosteal reaction, is there any

2:30

surrounding bone marrow or soft tissue edema,

2:33

is there any joint effusion, or does the lesion

2:35

cause cortical disruption and extend beyond

2:37

the bone into these adjacent soft tissues.

2:43

So let's look at our first case.

2:51

So there's a little history here.

2:53

Young female with posterior thigh mass,

2:55

now with worsening swelling and pain.

2:58

These are the sagittal T2 FATSAT images.

3:01

I'm scrolling from medial to lateral side,

3:05

give you a few seconds to look at these

3:07

images and figure out what's going on.

3:11

That's a sagittal T1 FATSAT,

3:19

and this is a post-contrast T1 FATSAT.

3:22

I would like you to compare the images at the

3:28

bottom: T1 and T1 FATSAT post-contrast.

3:34

I'm looking at these images side by side

3:37

to see if there is any real enhancement

3:39

within the abnormality or not.

3:43

And there's a small question for you for this case.

3:47

So what do you all think is going on in this case?

3:50

So what complication associated

3:52

with this entity are we seeing here?

3:53

Is it malignant transformation?

3:55

Is it hematoma from pseudoaneurysm rupture?

3:58

Is it bursitis or fracture

4:00

and hematoma formation?

4:05

Let's look at the answers now.

4:07

So, the majority

4:08

of you answered malignant transformation,

4:10

but that is not the correct answer.

4:11

The correct answer is bursitis,

4:14

and unfortunately none of you picked it up.

4:16

So let's, let's review this, um, and

4:18

see why that's the correct answer.

4:20

So, first let's see what an osteochondroma is.

4:23

It's the most common benign bone tumor.

4:26

Um, 20 to 50% of the benign bone tumors, um,

4:30

constitute 20 to 50% of all benign bone tumors.

4:33

Um, usually seen in younger individuals.

4:35

Peak incidence in the second decade.

4:37

It's classically seen, uh,

4:39

at the end of the long bones.

4:40

Um, usually arising from the metaphysis,

4:43

they can be single or multiple.

4:45

Multiple are usually seen in a hereditary

4:48

disorder known as multiple hereditary exostoses,

4:50

and you get two flavors of osteochondromas.

4:53

They can either be pedunculated, as we see in this case

4:56

where there is a stalk, uh, and the lesion extends into

5:01

the soft tissues, or they can be sessile, where there

5:02

is a broad zone of transition to the underlying bone.

5:05

What do we see on imaging,

5:07

or how do we make an imaging diagnosis?

5:09

It's pretty straightforward.

5:10

It's an easy diagnosis to make

5:12

when you see a bony outgrowth.

5:14

And the imaging hallmark is when it

5:16

demonstrates cortical and medullary continuity.

5:19

So the cortex of the parent bone is continuous with the

5:22

cortex of the lesion and the medulla of the parent bone

5:25

is continuous with the medullary cavity of the lesion.

5:28

And they typically grow away from the joint.

5:30

And these are the features that will allow

5:32

you to differentiate it from the other bones.

5:35

Uh, some of the similar looking entities such

5:37

as a bone spur. A bone spur is usually

5:39

small and it grows towards the joint, whereas

5:42

an osteochondroma goes away from the joint.

5:45

And you have some periosteal reactions,

5:47

uh, lesions like parosteal osteosarcoma.

5:50

But then, uh, it'll have a cleft sign and it

5:53

will not show corticomedullary continuity.

5:55

Similarly, this entity known as BPOP,

5:59

bizarre porosity or osteochondromatous proliferation,

6:03

is a reactive bone and cartilage

6:06

proliferation in the soft tissues arising from

6:08

the periosteum, but this also doesn't demonstrate

6:11

corticomotillary continuity with the parent bone.

6:13

So these are the imaging features that help

6:15

you differentiate from other similar-looking

6:17

entities, and osteochondromas are typically

6:21

asymptomatic unless complications occur.

6:24

So what are some of the complications

6:26

associated with osteochondromas?

6:28

Cosmetic and osseous deformity.

6:30

That's one of the most common reasons why

6:32

these patients present. The osteochondroma can

6:35

fracture when they're subjected to trauma,

6:38

and it typically involves the base of the lesion.

6:40

The bone outgrowth may displace

6:44

the surrounding vessels and cause stenosis,

6:46

occlusion, and pseudaneurysm formation.

6:49

It can compress the surrounding

6:50

nerves and cause nerve dysfunction.

6:52

For example, if there's an osteochondroma

6:54

arising from the proximal fibula, it can

6:56

compress onto the common peroneal nerve,

6:58

and the patient may present with foot drop.

7:01

And they can even result in bursa formation,

7:04

and this happens when there's friction between

7:07

the projecting bone and the overlying soft tissues.

7:09

And that's the answer in this case.

7:11

This was complex bursitis.

7:13

And obviously, the most dreaded complication of

7:15

osteochondromas is malignant transformation,

7:18

where you have associated soft tissue.

7:20

But the clue is to appreciate that this is

7:22

a more well-defined fluid collection.

7:26

It has a thick peripheral rim.

7:28

And when we compared the T1, pre-contrast T1

7:31

and post-contrast T1, there is really no internal

7:33

enhancement within the lesion because it was

7:35

intrinsically a T1 hyperintense to begin

7:39

with, and there are no nodular areas of enhancement

7:41

as you'll see with malignant transformation.

7:45

So malignant transformation is seen in less than 1% of

7:48

solitary osteochondromas, and then up to

7:52

2% to 5% of cases of hereditary multiple exostosis.

7:56

So HME has a higher incidence of malignant

7:59

transformation of osteochondromas than solitary osteochondromas.

8:03

And the other suggestive features are

8:05

when they continue to grow after skeletal

8:07

maturity or present with pain.

8:11

So what are the imaging features that are

8:14

suggestive of malignant transformation?

8:15

Obviously, when the patient presents with pain,

8:17

a lot of them, these are asymptomatic, so

8:20

really don't have to do anything about them.

8:22

But when they are symptomatic or they have continued

8:25

growth in a skeletally mature patient, that's

8:27

when we worry about malignant transformation.

8:30

Another important thing to look at in these

8:32

cases is to look at the cartilage cap.

8:34

So here is an example and an axial.

8:36

Um, T2 fat sat, and it's showing an osteochondroma

8:39

here, and it shows this peripheral bright T2 soft

8:42

tissue, which is the cartilage cap of the lesion.

8:44

And the malignant transformation

8:46

happens in this cartilage cap.

8:48

Studies have shown that if

8:50

this cartilage cap is more than

8:52

1.5 to 2 centimeters in thickness,

8:54

that suggests malignant transformation.

8:56

And MRI is one of the best modalities to evaluate this.

8:59

The other...

9:00

Okay.

9:00

Obvious findings suggesting malignant

9:02

transformation will be indistinguishability

9:05

of the outer surface, if there are focal areas

9:07

of radiolucency within the lesion, if there's

9:09

destruction of the adjacent bone, or if there are

9:11

scattered calcifications and a soft tissue mass.

9:15

So what's the treatment for these lesions?

9:17

Um, you just observe them if they're asymptomatic.

9:20

Excision is reserved for lesions

9:22

that will cause a cosmetic deformity.

9:23

In fact, that's one of the common reasons

9:25

why you will excise a benign osteochondroma.

9:28

Sometimes they can present with pain, and that can

9:30

be a hallmark, uh, for malignant transformation.

9:33

And even if they're symptomatic from complications, as we,

9:36

um, uh, discussed a few seconds earlier, that it can

9:40

impinge on surrounding vessels and nerves and can cause

9:43

problems. Or, if it interferes with joint function,

9:46

if it's close to a joint, that's also when excision

9:49

would be recommended. But excision of an osteochondroma

9:53

should, if possible, be postponed until treatment

9:55

in later adolescence because there will be

9:57

a chance of damaging the growth plate.

9:59

They're often close to the growth plate,

10:00

and in an immature skeleton, there will be a

10:03

chance of causing damage to the growth plate.

10:05

And also, there is still a growth potential.

10:08

So the incidence of recurrence is higher when you

10:10

excise them before skeletal maturity is achieved.

10:14

If there is a malignant transformation, then you're

10:16

going to treat them with wide surgical resection

10:19

and limb salvage, and chemotherapy and radiation

10:22

only if there is a dedifferentiated chondrosarcoma.

10:25

So going back to the case, I'll show

10:27

you the T1 and post-contrast again.

10:30

Unfortunately, I don't have subtraction images that

10:32

would have been really helpful in this case, but

10:35

the pre-contrast and post-contrast T1 looks exactly

10:38

the same, with no exaggerated internal enhancement.

10:41

And if we know that these can cause complex bursitis

10:45

too, which can look like this, um, then we can

10:47

make a right diagnosis and prevent unnecessary

10:51

biopsy and aggressive treatment in these cases.

10:53

So this was a case of osteochondroma causing

10:56

complex bursitis and not malignant transformation.

11:01

Another case here, uh, which is a more ant mini

11:03

appearance where you see this osseous outgrowth,

11:06

you can appreciate the corticomedullary continuity.

11:09

The pathologist described these lesions as cauliflower

11:11

lesions on, um, gross examination, and this is exactly

11:16

how it's looking like, a cauliflower-like lesion.

11:20

Another case here on MR sagittal T1

11:22

weighted images, you see an osteochondroma

11:24

rising from the proximal fibula.

11:27

You can appreciate this nice

11:28

corticomedullary continuity.

11:30

And on axial images, I've already shown you these

11:32

images. On the periphery of this

11:36

lesion, there is this peripheral T2 hyperintense

11:38

soft tissue that corresponds to the cartilage cap.

11:41

And it's important that we measure the thickness of

11:43

the cartilage cap, and if any time it gets more than

11:46

1.5 to 2 centimeters in thickness, we suggest that

11:49

this might, um, be a malignant transformation and

11:52

more aggressive treatment is required for such cases.

11:55

Similarly, another case here,

11:57

more in an elderly person.

11:58

This lady was around 45 years old, presented with pain.

12:02

So that's another, that is some

12:05

presentation for these lesions.

12:06

And on imaging, there was a thick cartilage cap.

12:09

Um, and this is where we worried about malignant

12:14

transformation, but this was biopsied and it

12:16

turned out to be a grade one chondrosarcoma.

12:20

And this was just, um, um, they did a simple resection.

12:25

And, um, for this case, I'm just following it up.