0:00

Let's move on to our next case. Okay,

0:05

so young female with elbow pain and swelling. Can we have the question

0:09

please for this? So the question is, what will be the best set

0:13

of differentials for this case? So obviously, you'll have a differential

0:17

for this kind of an imaging appearance, and the options are ABC and

0:22

GCT, chondroblastoma and GCT, ABC and a non ossifying fibroma, and a chondroblastoma

0:32

and an ABC. Let's look at the answers.

0:36

Okay, divided between two, the options selected by majority were ABC and

0:42

GCT, and also chondroblastoma and GCT. The correct answer here is ABC and

0:49

GCT. The reason it's not a chondroblastoma is because the visors have fused.

0:55

The age is 24, which is slightly older for a chondroblastoma. You do

1:00

get burnt out chondroblastomas at a later age after fusion of the epiphysis,

1:04

but they usually have a thick sclerotic rim,

1:07

and they're usually not expansile like this. Being lytic expansile lesions

1:14

in the epiphysis reaching the subchondral bone, in a younger patient,

1:19

GCT will always be a differential. And also, since this patient is less

1:22

than 30 and has lot of expansion and looks like a benign lesion with

1:27

well circumscribed margins, the second differential would be an ABC.

1:30

And this was the MR in this case, and

1:33

we see nice fluid fluid levels in this lesion. This wasn't a aneurysmal

1:41

bone cyst. And some companion cases. Another lesion in the distal radius,

1:50

lot of expansion and trabeculations. Again, the differentials that you'll

1:56

entertain for such appearance will be the patient is young, this is a

2:00

17 year old patient. The differentials that you'll consider because the

2:05

visors have closed will be a GCT, and then the other thing would

2:08

be an ABC. And given the younger age, 17 years, GCTs are usually

2:14

seen after 30 years of age, from a younger patient, when you have

2:18

such an aneurysmal lesion, it's really, really expansile. The

2:23

diagnosis that we need to consider in this patient is this ABC and

2:27

this is cross sectional imaging helps to confirm the diagnosis, and it shows

2:31

these nice blood fluid levels in this case.

2:37

Predominantly cystic, expansile, with septation and blood fluid levels,

2:43

so that would be an ABC. We'll review some quick facts about this

2:50

entity. These are benign, expansile tumor like bone lesions composed of

2:56

numerous blood full spaces, channels. Again, seen in young,

3:01

so less than 30 years is what we need to keep in mind

3:04

for these lesions. Location is typically eccentric. Most common location

3:10

is metaphysis, but they can be in the metaphysis or even in epiphysis as

3:14

we saw in these two cases. Usually long bones,

3:19

they can also happen in spine and sacrum.

3:22

Posterior elements of the spine is a good location for an aneurysmal bone

3:26

cyst up to 20%30% are seen in this location.

3:29

And they're also seen in epiphysis, epiphyseal equivalents, or in apophysis.

3:32

These are rare but important locations. Imaging hallmarks, they are named

3:39

for their aneurysmic appearance. They're actually very aneurysmal, and that's

3:43

why they are called aneurysmal bone cysts. If you see a lesion that

3:47

is really expansile, a younger patient when you're considering a benign

3:52

lesion, that's when we need to think of aneurysmal bone cysts. And this

3:55

is what Dr. Clyde Helms says about this "I use expansion and below

3:59

the age of 30 as fairly rigid guidelines and seldom miss the diagnosis

4:03

of ABC." I can't find a better explanation than that, so I'm just

4:07

quoting him as it is here. If you keep these two things in

4:11

mind, you'll often make the diagnosis of ABC accurately.

4:15

And on conventional imaging helps to confirm the diagnosis by demonstrating

4:19

multiple fluid levels. Other lesions that can show fluid levels are

4:24

a secondary ABC. Even some malignant lesions like telangiectatic osteosarcoma,

4:29

but there are ways to differentiate between the two. And the main thing

4:33

would be to look for any associated soft tissue, cortical disruption,

4:36

extraceous soft tissue. All these features suggest that this is probably

4:40

either a secondary ABC or a telangiectatic osteosarcoma or something else

4:46

and not a primary ABC. Another thing to keep in mind and like in

4:50

spine, similar to giant cell and chordoma, this

4:55

lesion can traverse adjacent vertebral bodies. It can go from one to

5:02

the adjacent vertebral body or intervertebral discs or may extend along

5:07

the ribs. It doesn't have to be localized to one bone.

5:10

It can traverse and involve the adjacent bones as well. ABCs are of two

5:17

types. You can have a primary aneurysmal bone cyst, majority of them are

5:21

primary, and you can occasionally have a secondary where you have a primary

5:25

bone tumor that undergoes aneurysmal bone cyst transformation. And some

5:31

of the common benign lesions that typically show this aneurysmal bone formation

5:37

is non ossifying fibromas, fibrous dysplasia, chondroblastoma, giant cell

5:42

tumors, osteoblastoma, and telangiectatic osteosarcoma are listed, because

5:47

they have very predominant fluid fluid levels just like ABC. But as I

5:51

said, there are ways to differentiate between a benign lesion versus the

5:54

cystose aggressive. Presence of an enhancing soft tissue differentiates

6:00

a secondary ABC from a primary ABC. How are they treated?

6:04

They are treated by curettage followed by bone grafting. Most of the benign

6:08

bone tumors are treated this way. But again, this is also associated with

6:13

high risk of local recurrence. So you may

6:16

wanna ablate the cyst margin with argon beam or by using a high

6:21

speed burr, electrocautery, cryotherapy, or embolization. Embolization because

6:25

they're too vascular, sometimes especially in the spine. So to get control

6:29

on their size, you can do an embolization for these lesions. And for

6:34

spinal ABCs, again, the option is embolization. They can even try radiation.

6:43

But the preferred method by majority is radical resection for these. Otherwise,

6:47

they'll recur or they can cause mass effect and cause spinal compression,

6:50

cord compression. Few more companion cases is another young female. So if

6:56

you have a lytic lesion, which is eccentrically located in the metaphysis,

7:02

really expanding the cortex and has well circumscribed sclerotic margins.

7:07

And remember what Dr. Clyde himself said about these lesions, less than

7:13

30 years, and you have an aneurysmal lesion, it's going to be an ABC.

7:18

So this was also an ABC, and it showed these nice blood fluid

7:23

levels on cross sectional imaging. Another case here. So we have again a

7:31

young female, 27 year old, and has this expansile lytic lesion in the

7:36

spinous process of cervical vertebral body. So the differentials that we

7:40

are considering here would be an aneurysmal bone cyst and the other benign

7:44

bone tumor or a lytic lesion that can happen in the posterior elements

7:49

of the spine would be an osteoblastoma. But again, osteoblastoma with that

7:55

big, will have much thicker margins and will have osteoid matrix, whereas

7:59

there is no matrix in this lesion. So your differentials are osteoblastoma

8:05

and ABC, and we'll favor ABC given no osteoid matrix, no sclerosis.

8:10

And if you can see, there are some fluid fluid levels in this

8:14

lesion as well, better seen here. You can see some

8:20

nice blood fluid levels in this case. So also remember this entity

8:25

in long bones, metaphysis or epiphysis, but really expansile and eccentric

8:31

posterior elements of the spine and, also as I said, they are also

8:36

seen in small bones, which are equivalent of epiphysis. Here we have loosened

8:42

seen the cuboid. You really don't see much on the oblique and you don't

8:47

have... But on MR imaging, you have this nice lesion in the cuboid which

8:52

is predominantly cystic, no solid component, and all these cystic spaces

8:56

have blood fluid levels so typical for aneurysmic bone cyst. So

9:04

this is a summary, less than 30 years, if you have a well

9:09

circumscribed, but really expansile bone tumor, think of an aneurysmic bone

9:13

cyst. They can be primary or secondary. And when you have fluid fluid levels

9:17

on cross sectional imaging, think of ABC, which can be primary,

9:22

but it can be secondary. So think of any of the primary lesions that

9:25

can have ABC formation, and also make sure you rule out something like

9:30

more varicose, like the osteosarcoma, which will have more aggressive appearance,

9:34

more cortical destruction, and more associated soft tissue.