0:00

Let's move on to our next case.

0:04

Okay, so we have a young female with

0:06

increasing leg pain and discomfort.

0:09

AP and lateral radiographs of the leg.

0:14

Radiographs of the knee as they give a closer

0:16

look at this lesion here in the proximal tibia.

0:20

And these are the MR findings.

0:24

Sagittal

0:24

T2 fat saturation, Sagittal

0:27

T1 and Sagittal post-contrast.

0:34

Can we have the next

0:34

question, please?

0:36

So what is the diagnosis?

0:37

Your options are: Is it a benign enchondroma?

0:40

Is it a low-grade chondrosarcoma?

0:41

Is it a bone infarct or is it

0:43

a clear cell chondrosarcoma?

0:47

Okay, let's look at the answers.

0:52

Majority of you said benign enchondroma.

0:55

Okay, so, um, the correct answer

0:57

here is a low-grade chondrosarcoma, and

0:59

let's see why that's the correct answer.

1:02

So quick review on, um, intramedullary

1:05

chondroid lesions, um, so whenever we see an

1:09

intramedullary chondroid lesion, um, the often

1:11

diagnostic dilemma is: Is it a benign

1:13

enchondroma versus a low-grade chondrosarcoma?

1:16

So what are enchondromas?

1:17

These are, um, it's a benign hyaline cartilage

1:21

producing tumor of the medullary bone, uh, classically

1:24

seen in younger individuals with a peak incidence of

1:27

10 to 30 years. Um, location: it's seen in long bones,

1:31

and it's also the most common cystic lesion of

1:34

the phalanges. So if you have a lytic expansile lesion

1:37

in the phalanges without any matrix mineralization,

1:40

um, statistically, it's going to be an enchondroma.

1:43

There are other differentials too, but the most

1:45

common lesion to happen there is an enchondroma.

1:47

It's asymptomatic in most large bones, and in phalanges,

1:51

it may present with pain from a pathologic fracture.

1:54

So, um, what are the imaging features?

1:57

Um, it's often a well-circumscribed lesion,

1:59

um, usually seen as a lucent defect

2:02

in the metaphysis of the long bones.

2:04

So it's usually seen in the metaphysis.

2:06

It's often central.

2:07

It can sometimes be eccentric.

2:10

It can be expansile or it can be non-expansile,

2:13

but in long bones, it will invariably contain this

2:16

calcified chondroid ring and arc type of matrix

2:19

that we can see here, nice central

2:22

intramedullary lesion with the ring and arc

2:25

type of chondroid type of matrix calcification.

2:28

So this is an imaging, um, hallmark of an enchondroma,

2:32

but you never see a matrix

2:34

mineralization when this lesion happens

2:36

in the phalanges for unknown reasons.

2:39

And how do these cartilage low-grade or

2:43

intramedullary chondroid lesions look on MR imaging?

2:46

Um, they are very T2 bright and have these

2:48

peripheral, uh, nodular margins, um, and this

2:52

high signal is typical of cartilage lesions.

2:55

And the enhancement pattern is also fairly typical,

2:57

where you have this peripheral septal enhancement,

3:01

which is accentuating those cartilage lobules.

3:06

So, enchondromas, the benign enchondromas

3:08

are often asymptomatic and incidentally detected,

3:11

um, but they can histologically

3:16

mimic a chondrosarcoma, and that's why a painless

3:19

chondroid lesion should never be routinely biopsied.

3:22

Because if you recommend biopsy for these lesions

3:25

to confirm the diagnosis or to see if there is any

3:27

malignant transformation or not, um, remember that

3:30

histologically, it's not possible to differentiate

3:33

between a benign enchondroma and a chondrosarcoma.

3:36

And the diagnosis comes from looking

3:39

at the radiographs and MR imaging in these cases.

3:42

So what are some of the worrisome features where

3:44

we suspect a chondrosarcoma rather than a

3:46

benign enchondroma? When it happens at an older age.

3:52

Male gender is also a risk factor

3:57

when they clinically present with pain.

3:59

So often they're asymptomatic, but if they're

4:01

presenting with pain, that's always a red herring.

4:05

If you see a cartilage lesion in flat bones,

4:07

it's often going to be a malignant lesion.

4:10

A cartilage lesion in the epiphysis is often

4:12

going to be a malignant lesion where

4:14

we consider clear cell chondrosarcoma.

4:16

If the lesion is larger than five to six centimeters

4:19

in diameter, that's when we get worried that

4:21

this is getting transformed into malignancy.

4:24

And when the lesion causes endosteal

4:26

scalloping, and if it's more than two-thirds

4:28

of the cortical thickness, or for more than

4:31

two-thirds of the length of the lesion, um, so.

4:35

These are some of the really worrisome features

4:37

when we suspect malignant transformation.

4:40

And when the matrix mineralization becomes

4:42

less than two-thirds of the lesion, a part of

4:45

the lesion starts showing a clear matrix is

4:48

also when we suspect malignant transformation.

4:51

When you have cortical remodeling destruction,

4:53

obviously these are worrisome features.

4:55

Anytime there's cortical disruption, you get worried.

4:58

If there is aggressive periosteal reaction, if

5:00

there's a pathologic fracture through the lesion,

5:02

and if there's an associated soft tissue mass.

5:06

So how do we treat these for solitary

5:08

enchondromas in the hand and long bones?

5:10

And even in, um, both in phalanges and long

5:14

bones, simple curettage followed by bone

5:16

grafting is sufficient and will offer cure.

5:20

And then we have to just follow

5:21

them up for healing and recurrence.

5:23

But for higher-grade lesions,

5:25

you'll require a wider excision.

5:27

So going back to our case, why

5:29

was it a low-grade chondrosarcoma?

5:31

Now we have reviewed the features.

5:32

It's definitely more than five centimeters in size.

5:36

It's causing a lot of endosteal scalloping.

5:38

So if you see there is endosteal

5:40

scalloping, the cortex here, um, is thicker.

5:43

And as we come at the level of the endosteal

5:46

scalloping, the cortex gets really thinned out.

5:49

And though there are no obvious aggressive features like

5:52

cortical destruction or extraosseous soft tissue mass,

5:55

the size of the lesion and presence of

5:57

endosteal scalloping, which is deep, is enough

6:00

to call this a low-grade chondrosarcoma.

6:03

Even on radiographs, we can see similar features,

6:06

um, that it's causing endosteal scalloping,

6:09

and it's much larger than five centimeters.

6:13

Okay, a few companion cases.

6:18

If you see a lesion like this, which is obviously

6:21

you're seeing a lesion in the metaphysis, shows this

6:24

classic ring and arc type of matrix mineralization.

6:27

So this is an enchondroma.

6:28

Now this, is this a low-grade chondrosarcoma?

6:30

We'll measure the size.

6:31

It's roughly around five centimeters.

6:33

And I really don't see any endosteal

6:35

scalloping associated with this lesion.

6:37

That may be the first feature.

6:39

And then later on will come cortical

6:40

destruction and extraosseous soft tissue mass.

6:43

So since we are not seeing any worrisome features,

6:45

we just call this a benign appearing

6:49

chondroid lesion with no aggressive features.

6:51

That's how we should read these lesions

6:54

out rather than committing to an

6:56

enchondroma or a low-grade chondrosarcoma.

6:59

The moment you say low-grade

7:00

chondrosarcoma is not entirely excluded.

7:02

The word chondrosarcoma alerts

7:05

the physicians and the patients themselves, and

7:07

they will go ahead and biopsy those lesions.

7:09

But again, as I said, biopsy is not the

7:11

discriminator between an enchondroma

7:13

versus a low-grade chondrosarcoma.

7:15

It's more of the imaging features based

7:17

on which we make that distinction.

7:19

And why is it important?

7:20

Because it changes the management.

7:21

A low-grade enchondroma can be

7:25

ignored, um, and would not need any biopsy.

7:30

Close follow-up or further treatment, whereas a

7:32

low-grade chondrosarcoma will require treatment

7:34

and regular follow-up because there'll be a certain

7:36

risk of recurrence or a de-differentiation into a

7:39

higher-grade chondrosarcoma at a later date.

7:44

Another companion case here, again, we see a

7:47

lesion in the metaphysis, centrally located,

7:49

classic ring and arc type of matrix mineralization.

7:53

Now the worrisome feature here is it goes to

7:55

out in the periphery, but I'm still not

7:57

seeing a whole lot of endosteal scalloping.

7:59

So we look at the MRI.

8:00

And on MRI, there are certain areas where it

8:05

reaches up to the cortex, but yes, it really

8:07

doesn't cause a whole lot of endosteal scalloping.

8:13

But it's this area where it causes deep endosteal

8:16

scalloping, and the cortex is almost thinned out.

8:18

So this lesion is more than five centimeters

8:21

and it's causing deep endosteal scalloping.

8:23

So this was a low-grade chondrosarcoma.

8:27

which they did curettage and cement

8:29

packing, and stabilized it with a plate.

8:31

And the difference between a benign enchondroma

8:33

versus a low-grade chondrosarcoma is this will require

8:36

closer follow-up to look for recurrence or de

8:39

differentiation.

8:43

Another case here, where

8:45

again we have a central medullary

8:48

lesion with ring and arc-type matrix.

8:51

So an intramedullary chondroid lesion,

8:56

but this patient was elderly and presented with pain.

8:59

So got further imaging with MRI.

9:01

And here we have this large soft tissue that breaks

9:05

the bone and gets into the surrounding soft tissues.

9:08

And you can see the disruption

9:10

of the cortex very well here.

9:11

The soft tissue breaks the cortex, extends

9:14

beyond the cortex into the soft tissues.

9:16

So this on biopsy was a de-differentiated

9:19

chondrosarcoma arising from a pre-existing

9:21

benign enchondroma, and he later on

9:24

went on to develop pulmonary metastasis.

9:27

They did distal femoral resection,

9:29

replacement with knee arthroplasty.

9:33

You can look at the soft tissues; this

9:35

record even after complete resection.

9:38

So that's the thing that we worry about in these cases.

9:44

Um, sometimes when they present like

9:47

this, it's hard to differentiate something

9:49

that can look similar to a bone infarct, and sometimes

9:52

it's hard to differentiate between the two.

9:54

So here we have a classic example of an

9:56

enchondroma, and here is a classic bone infarct.

9:59

Enchondroma, usually the peripheral margin is not

10:01

sclerotic, and here it's the periphery of the lesion

10:03

that's sclerotic and will be more serpentinous.

10:06

And chondrosarcoma, as we saw a few examples of, especially

10:10

if it's a worrisome, um, low-grade chondrosarcoma,

10:14

whereas bone in fat usually don't cause endosteal scalloping.

10:20

And you can, like we saw, uh, multiple osteochondromas; you can get multiple enchondromas too.

10:26

And there are certain syndromes associated with this.

10:29

So you have Ollier disease, where you get multiple

10:31

enchondromatosis, and Maffucci syndrome is where you have

10:34

multiple enchondromas associated with soft tissue

10:37

hemangiomas.

10:38

Again, the

10:38

significance of these syndromic manifestations is

10:41

it's a much higher risk of malignant transformation

10:43

as compared to solitary benign chondroid

10:46

lesions, and the risk is as high as 25 to 30%.

10:52

So to summarize for, um, intramedullary

10:54

chondroid lesions, uh, the question is if it's

10:58

just a benign enchondroma that we don't

11:01

need to do anything about versus it's a low

11:03

grade chondrosarcoma which will require some

11:05

aggressive treatment and rigorous follow-up.

11:08

Uh, if you see a small lesion, uh, central

11:12

intramedullary in the metaphysis with ring and arc type

11:15

of matrix mineralization less than five centimeters

11:17

in size, you can confidently dismiss this as a

11:21

benign chondroid lesion with no aggressive features.

11:24

Then you have a little larger lesion, but again,

11:26

no aggressive features, no endosteal scalloping.

11:29

So we can maybe do a follow-up for

11:31

this, but this is definitely much larger

11:34

with much deeper endosteal scalloping.

11:36

So this is going to be a low-grade

11:37

chondrosarcoma that will require curettage,

11:40

um, and packing, and then a close follow-up.

11:43

And this is an obvious example of a dedifferentiated

11:47

chondrosarcoma from a pre-existing enchondroma,

11:49

again will require more aggressive management.