0:01

Let's move on to our next case.

0:04

So a younger patient, 20-year

0:06

old female, with knee pain.

0:08

Here we have the AP and lateral

0:10

radiographs of the knee.

0:15

Let's zoom this up for you.

0:17

And then we have the MR images,

0:22

coronal T2 fat saturation, coronal T1,

0:29

axial T2 fat saturation, and axial proton density.

0:40

Can we have the next question, please?

0:43

So this lesion was biopsied and pathology

0:45

showed giant cell tumor of bone.

0:47

Which immunotherapy medication has shown

0:49

promising results in the management of these lesions?

0:51

Your options are femoralizumab,

0:52

nivolumab, imatinib, and denosumab.

1:00

So this was a giant cell tumor,

1:01

and we'll do a quick review of this entity.

1:06

So let's see the answers for this question.

1:11

Okay, so the majority of you answered

1:12

correctly, it's Denosumab.

1:15

Okay.

1:16

So what are giant cell tumors?

1:18

These are benign but locally

1:19

aggressive neoplasms composed of uniformly

1:22

distributed osteoclast-like giant cells.

1:25

They constitute 20 percent of all benign bone tumors.

1:28

And the important things are that they

1:30

almost always affect a mature skeleton.

1:32

So they're usually seen after the

1:34

physis on radiographs, most commonly

1:37

in the third and fourth decades of life.

1:40

Location, they typically occur

1:42

in the epiphysis of the long bones.

1:44

They can also be seen in the spine.

1:47

If they occur in the spine, then

1:49

the sacrum is the most common location.

1:51

Giant cell tumors also occur in apophysis,

1:55

which is also an epiphyseal equivalent.

1:57

So that can be seen in trochanter, tuberosity,

2:02

small bones like calcaneus, carpal bones,

2:04

and patella, which are the apophysis. And in fact,

2:09

GCT is the most common neoplasm of the patella.

2:13

So what are the imaging hallmarks for this lesion?

2:15

So Dr. Clyde Helms, an authority in benign bone tumors,

2:19

has listed four radiographic criteria in his book, and we follow it.

2:21

If you follow this, we should be able to give

2:24

a specific diagnosis in the majority of the cases.

2:30

So giant cell tumors occur in

2:31

patients with closed epiphysis.

2:34

The lesion must be epiphyseal

2:36

and abut the articular surface.

2:38

So they get to the epiphysis and they get

2:40

to the subchondral bone almost always.

2:43

These lesions are said to be

2:44

centrically located in the bone.

2:46

So as you can see here, there is centric

2:48

rather than central, and they should have

2:51

sharply defined borders or zones of

2:54

transition, and that's not sclerotic.

2:56

So if you have a lesion in a younger

2:58

patient, but with closed epiphysis, and a

3:01

centrically located lesion in the epiphysis

3:03

with well-defined margins, but non-sclerotic

3:06

margins, it's going to be a GCT the majority of the time.

3:10

So there are other differentials too, but the majority

3:12

of the time it's going to be a giant cell tumor.

3:15

Now, occasionally, giant cell tumors can have

3:17

aggressive features, like they can be more expansive

3:20

and cause cortical disruption, and they can have an

3:22

associated soft tissue on cross-sectional imaging.

3:25

Occasionally, you can see fluid-fluid levels

3:28

within these lesions on cross-sectional imaging,

3:30

and that represents secondary ABC formation

3:34

or secondary formation of an aneurysmal bone cyst,

3:36

which is seen in up to 14 percent of the cases.

3:40

So how do we treat this?

3:41

Treatment is often surgical, primarily consisting

3:44

of curettage and cement placement,

3:47

but this tumor is notorious for local recurrence.

3:51

So that's why some people also call

3:52

it a quasi-malignant lesion.

3:54

It is not a malignant lesion,

3:57

but it does recur locally quite often.

4:01

With rates up to 15 to 25%.

4:05

When do we suspect recurrence in these cases?

4:07

Once you treat this, we always

4:10

follow them closely for recurrence.

4:12

Whenever we see the development of a new

4:14

lucency at the bone-cement interfaces, that's

4:17

when we suspect recurrence in these cases.

4:19

Denosumab is a monoclonal antibody

4:22

that has recently shown activity against the

4:25

neoplastic cells of this tumor,

4:29

and it's a promising treatment

4:30

therapy for these lesions.

4:35

GCTs can also result in lung

4:36

metastases, but those are benign.

4:38

It just happens from hematogenous seeding at the

4:40

time of treatment of the lesion, and very rarely

4:43

GCT can actually undergo malignant transformation.

4:47

What are some of the differentials

4:48

that we need to consider when we are

4:50

looking at radiographs with that

4:52

classic description that we just saw?

4:55

One of the closest differentials for giant cell

4:57

tumors is an aneurysmal bone cyst because it

5:00

also happens in the metaphysis. It's lytic

5:04

expansile, but there are certain differences.

5:06

It's usually seen in younger individuals,

5:08

so it can be seen after fissure closure too.

5:11

An aneurysmal bone cyst is also eccentric

5:14

like GCT, but it's usually much more expansile.

5:18

Another confident way to differentiate

5:20

between the two is on cross-sectional imaging.

5:22

If we see some soft tissue component, then

5:25

you know it's a secondary ABC. If the

5:28

primary features are of a GCT, then you know

5:30

it's a GCT with secondary ABC transformation.

5:33

In a primary ABC, there should

5:34

not be any soft tissue component.

5:36

It should predominantly be a lytic septated cystic

5:40

lesion with blood fluid levels and no soft tissue.

5:44

Usually, again, seen in younger individuals,

5:47

whereas GCT is seen in the third and fourth decades.

5:50

Another differential for

5:52

an epiphyseal lesion is a chondroblastoma.

5:55

Both chondroblastoma and GCTs are epiphyseal.

5:58

They both can show secondary ABC formation, but

6:02

the features unique to chondroblastoma are that they incite

6:04

a lot of bone and soft tissue edema around them.

6:08

They often occur in younger individuals

6:09

and the physis are still not fused.

6:12

They have a sclerotic margin and they, uh,

6:15

some cases show chondroid matrix mineralization too.

6:18

These are two differentials in younger

6:20

individuals and two differentials that we need to

6:23

consider in patients older than 40 years of age.

6:25

Anytime you have a lytic lesion in a patient who's

6:28

older than 40 years, myeloma and metastasis is always

6:31

a consideration, but you'll have a suggestive history.

6:34

On cross-sectional imaging,

6:36

we can further refine the diagnosis.

6:38

Clear cell chondrosarcoma happens in the epiphysis.

6:41

If you have a lesion with chondroid

6:44

matrix in the epiphysis, that's when we

6:47

consider clear cell chondrosarcoma.

6:49

GCT usually will not have,

6:51

or doesn't have a chondroid matrix.

6:53

There are certain subtypes of osteosarcoma such

6:56

as telangiectatic osteosarcoma that also show fluid

6:59

levels, um, and can mimic a GCT with

7:02

secondary ABC, but telangiectatic osteosarcomas

7:05

are much more aggressive and have a lot more

7:09

cortical destruction in surrounding soft tissue.

7:12

Okay, so going back to our case.

7:16

Here we have a younger, I gave

7:18

you the history, a 20-year-old female.

7:20

She had this lytic expansile lesion,

7:22

which is eccentrically located in the epiphysis of

7:25

the distal femur with well-circumscribed non

7:28

sclerotic margins reaching the subarticular bone.

7:31

That would be a GCT.

7:34

That was the MR, um, and they're

7:36

usually intermediate, uh, to darker signal

7:39

intensity on, um, T2-weighted images.

7:43

Looking at some companion cases, um, another

7:48

lesion has that classic description of

7:51

being eccentric, lytic, reaching the subchondral

7:54

bone with non-sclerotic well-circumscribed margins.

7:58

The only difference is there are a lot more

8:00

trabeculations within this lesion as compared to a usual GCT.

8:08

So here on cross-sectional imaging on MR,

8:11

we saw that this lesion is predominantly cystic

8:14

and on sagittal images, you can even see

8:19

blood-fluid levels.

8:20

I think it's better seen on axial images.

8:24

Yeah, we can see some blood-fluid

8:26

levels in these cystic spaces.

8:27

So this was, uh, a giant cell

8:30

tumor with secondary ABC formation.

8:31

So how do we differentiate between a primary

8:34

ABC versus a giant cell with secondary ABC?

8:37

First of all, it's the age.

8:38

Uh, this was, uh, um, I don't have the age listed

8:41

here, but, uh, a 50-year-old, uh, and, uh, ABCs

8:47

usually you don't, um, pick them in an older age group.

8:50

If they have to present, they

8:52

present earlier, the primary ABCs.

8:54

So the age group favors, um, a GCT with

8:57

secondary ABC formation and the expansion.

8:59

ABCs are usually much more expansive because

9:02

that's how they are named: aneurysmal bone cyst.

9:05

There's really not much of expansion in this lesion.

9:07

And the biopsy may have shown some giant

9:10

cells, giant cells that are typical for these tumors on histopath.

9:18

Okay, next case, Brewer, Robert.

9:24

Uh, we have, um, a lytic lesion in the metaphysis, sorry,

9:30

the epiphysis reaching to the subchondral bone.

9:32

Um, no matrix mineralization, though it is

9:35

not eccentric on the frontal radiograph.

9:37

But, um, on the sagittal, uh, it looks

9:39

eccentric along the anterior cortex.

9:42

So this was treated, but this was a giant cell tumor.

9:44

This was treated with cement packing,

9:47

uh, with stabilization with nails.

9:49

And this is, um, the CT showing a nice, um,

9:54

interface between the cement and the bone.

9:57

And obviously, as I said, we have to follow these

9:59

lesions up to see, um, because they're known for

10:02

recurrence and on the follow-up radiograph, um, here.

10:07

We have the bone and the cement interface, but

10:09

on the follow-up radiograph, we see a new lucency

10:12

that has developed at the bone-cement interface.

10:14

Um, so this raised concern

10:18

for recurrence in this setting.

10:21

And this is the CT, again, a comparison CT, um,

10:25

here showing no lucency, a tight bone-cement

10:28

interface, and here there is soft tissue

10:31

between the cement and the bone.

10:35

So this was, um, later biopsied and shown

10:38

to be a recurrence of giant cell tumor.

10:41

And this new area was additionally cemented and fixed.

10:45

So look out for recurrence in these cases.

10:50

So to summarize, we have this classic description

10:52

that will help you clinch the diagnosis.

10:54

In a mature skeleton, if you have an eccentric

10:58

lytic lesion in the epiphysis extending to the

11:02

circumscribed non-sclerotic margins, that's

11:05

your classic description for giant cell tumor.

11:08

They can have secondary ABC formation,

11:10

and they're known to have local recurrence.

11:12

So on follow-up studies, what we need

11:13

to look for is, um, new lucency at the

11:16

bone-cement interface in these cases.