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267 Cards in this Set

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What must be done to aneurysmal bone cyst sometimes before resection?
Preoperative embolization
Do aneurysmal bone cysts have predilection for epiphysis?
No. No special predilection.
When an aneurysmal bone cyst occurs in the epiphysis, what is usually true?
The ABC is secondary to another process which commonly occurs in the epiphysis.
In adults, what process is this most commonly?
Giant cell tumor
In kids and adolescents, what process is this most commonly?
Chondroblastoma
What other processes can epiphyseal aneurysmal bone cyst be due to?
Clear cell chondrosarcoma


Lytic phase of Pagets


Intraosseous ganglion
When you have an aneurysmal bone cyst that involves the end of bone, what is true about it.
It is presumed to be superimposed on Giant cell tumor or chondroblastoma.
What other lesions (non-epiphyseal) are aneurysmal bone cysts associated with?
Chondromyxoid fibroma


Fibrous dysplasia
How common is chondromyxoid fibroma?
Very rare
What is true of chondromyxoid fibroma and aneurysmal bone cyst?
Most CMFs have associated ABCs
How common is fibrous dysplasia?
Very common
What is true of fibrous dysplasia and ABC?
Fibrous dysplasia is rarely complicated by ABC. However, since fibrous dysplasia is so much more common than CMF, you are more likely to see ABC secondary to fibrous dysplasia than CMF.
What other class of lesions can ABC be associated with?
Malignant tumors
How common is this?
Very uncommon
What part of the spine does ABC affect when it occurs there?
Posterior elements primarily.

However, it can sometimes extend into the vertebral body.
What is the peak age for detection of fibrous cortical defect / nonossifying fibroma?
8 - 20 years
What is the difference between NOF and fibrous cortical defect?
Same histology, but name changes when the lesion is seen to extend past the cortex and into the medullary cavity
What is the clinical significance between these?
NOFs are more likely to fracture
How does the appearance of these lesions change when they begin to heal?
The rim becomes more and more sclerotic, and you can see a multiloculated appearance.
How does Hilary describe a fibrous cortical defect?
Cortically based eccentric lesion minimally expanding and thinning the posterior cortex. There is a narrow zone of transition, and it is purely lytic.
Where in the bone does fibrous dysplasia occur: Cortical or medullary?
Medullary
How does the matrix of fibrous dysplasia typically appear?
Clasically, ground glass appearance.
How else can it appear?
Purely lytic
If fibrous dysplasia is a fibrous matrix, why does it have any density at all?
Because of the presence of primitive woven bone, which is part of the matrix in fibrous dysplasia
What is a frequent variant appearance of the matrix?
Nodular foci of calcification
What are these calcifications due to?
Islets of chondroid matrix.
What is the characteristic appearance of fibrous dysplasia?

Zone of transition?
Narrow.
What can the zone of transition have associated with it?
May or may not have a sclerotic rim.
What are other characteristics of fibrous dysplasia?
Bony enlargement


Cortical thinning/scalloping
What pathology typically occurs with fibrous dysplasia?
Numerous fractures
What does the healing of these fractures result in?
Bowing deformities so commonly seen in fibrous dysplasia
What is the most common of these bowing deformities?
The coxa vara deformity known as Shepherd's crook
What percent of fibrous dysplasia is monostotic?
75%
In a patient with primary malignancy who is found to have a long segment of radiotracer uptake in a rib, what is the most likely diagnosis?
Fibrous dysplasia
What is the caveat here?
must be LONG SEGMENT tracer uptake, not just a focus
What area of involvement is more common in polyostotic form, but occurs sometimes in monostotic form?
Craniofacial involvement
What area is very commonly involved in both monostotic and polyostotic forms?
Femur
What area is much more commonly involved in the polyostotic form?
Small tubular bones of the hands and feet
What is a special form of polyostotic fibrous dysplasia?
McCune-Albright
What do these kids become symptomatic from first?
Endocrinopathy
What is does the endocrinopathy cause?
Precocious puberty
What percentage of McCune Albright patients are symptomatic with precocious puberty before the age of 10?
2/3
What is special about the distribution of fibrous dysplasia lesions in McCune-Albright patients?
Strong lower extremity predominance


Unilateral predominance
What does this cause in most McCune-Albright patients?
Limb-length discrepancy
What do almost all patients with this condition have complicating their bony lesions?
At least one fracture
What can happen to these people with craniofacial involvement?
Can get severe craniofacial deformities, with things like obliteration of paranasal sinuses and stenosis of cranial nerve foramina occurring
What is the peak age of diagnosis of the monostotic form of fibrous dysplasia?
1st and 2nd decades
What percent of monostotic fibrous dysplasia lesions occur in the long tubular bones?
40%
What are the 4 bones/areas most commonly affected by monostotic fibrous dysplasia?
1) Femur

2) Tibia

3) Ribs

4) Craniofacial bones
What was the previous name no longer used for osteofibrous dysplasia?
Ossifying fibroma
What is osteofibrous dysplasia pathologically?
Spicules of woven bone and peripheral lamellar bone in a fibrous matrix
Where does the lesion occur characteristically?
Anterior aspect of the tibia. Most commonly middle third, but can extend into the metaphyses
What does this result in?
Anterior tibial bowing
What is another location that osteofibrous dysplasia can occur?
Distal fibula
What is the typical course of the lesion?
Spontaneously regresses in most cases
How does the lesion look radiographically?
Similar to fibrous dysplasia, with ground glass appearance, narrow zone of transition, sclerotic rim.
What is an unique feature of the lesion?
Common to have skip lesions
What other lesion occurs in the same location?
Adamantinoma
What is the relationship of osteofibrous dysplasia and adamantinoma?
Osteofibrous dysplasia and adamantinoma are in the same spectrum of disease
What is the typical age of presentation of osteofibrous dysplasia?
Same as fibrous dysplasia: First and second decades.
So, how is osteofibrous dysplasia managed?
Follow up imaging is done in all cases. If the lesion is regressing, as most osteofibrous dysplasia does, nothing else needs to be done.


However, if the lesion is not regressing, more follow-up imaging will be done, and biopsy may be required.
What is the point of the biopsy?
To evaluate the lesion histopathologically, because some of these lesions may be adamantinoma-like osteofibrous dysplasia, and some may just be frank adamantinoma.
What is the second most common cartilage tumor?
Enchondroma
What area of the skeleton does enchondroma most commonly occur?
Short tubular bones of the hands.
What percent occur there?
More than 50%
What is the next most common place for enchondroma?
Long tubular bones
What percent occur in the long tubular bones?
25%
Which long tubular bones?
The usual 3: Femur, tibia and humerus
What other short tubular bones can enchondroma occur in, albeit much less frequently than in the hands?
Foot
When they occur in a long tubular bone, in what part of the bone do they occur?
Metaphysis or metadiaphysis
When they occur in a short tubular bone, what part do they occur?
There isn't much room in these bones, but typically diaphyses.
What symptom is concerning for malignant tranformation?
Pain. Enchondromas should be painless.
When is the possibility of malignant transformation of enchondroma considered?
If it is large (i.e. expansile lesion in long tubular bone) or if it is located centrally within the skeleton
What central bones can enchondroma involve?
Innominate bone (whole pelvis bone)


Shoulder girdle
About what percent of enchondromas occur in these areas?
5%
What is common appearance of solitary enchondroma?


Where does it develop?

What else is common?


What is MR appearance?
Lesion symmetrically expanding and thinning the cortex, with irregular matrix popcorn calcification, typical of cartilage. (Actually, matrix just has to have some degree of calcification, so can just have ground glass appearance). They can have associated microfractures.


Medullary cavity (does not start eccentrically)

Cortical expansion or thickening is common.


Low T1, High T2
What is the name for multiple enchondromatosis?
Ollier's disease
How are the lesions distributed?
Unilateral involvement.
What is the same lesion called with associated soft tissue hemangiomata?
Maffucci's
What is the clinically significant difference between Ollier's and Maffucci's?
Ollier's has a slightly higher risk of malignant transformation than what would be expected in multiple solitary enchondromas.

But Maffucci's has a much higher incidence of malignant transformation of its enchondromas.
What percent of patients with Maffucci's will develop malignant tranformation?
50%
What do patients with Maffucci's tend to die from?
Malignant transformation of their bony lesions
What are the inheritance patterns of Ollier's and Maffucci's?
There is none. Both Ollier's and Maffucci's occur sporadically.
What malignant tumor do these lesions transform into?
Chondrosarcoma
What is an additional risk in patients with Maffucci's?
Malignant tranformation of their soft tissue lesions
What is a common appearance of enchondroma in the long tubular bones?
Channel-like radiolucent areas within the metaphysis and metadiaphysis
What is this organ-piping appearance suggestive (but not pathognomonic) of?
Ollier's. Can be seen in solitary enchondroma, however (74-31 Resnick).
Where is this "organ-piping' appearance seen most commonly?
Proximal tibia


Lesser trochanter
What is the most common benign cartilaginous tumor (and also the most common benign skeletal tumor in general)?
Osteochondroma
What does a true osteochondroma have?
Periosteal, cortical, and medullary continuity with the parent bone
Why do we care if lesion is a true osteochondroma or not?
Because true osteochondromas have a hyaline cartilage cap
What are the complications of an osteochondroma?
Fracture


Nerve compression causing compression neuropathy



Bursa formation
What is a special complication of osteochondroma that occurs in the region of the popliteal fossa?
Pseudoaneurysm of the popilteal artery
How does this occur?
The popliteal artery is tethered proximally as it emerges from the adductor canal, and distally where is has its terminal branching into the anterior and posterior tibial arteries.

When an osteochondroma forms in this region, the popliteal can't get away, and the constant irritation of the vessel wall results in pseudoaneurysm formation.
What is the lifetime risk of malignant transformation of a single osteochondroma?
less than 1%
What does osteochondroma usually transform into when it does undergo malignant transformation.
Remember, it is the cartilage cap which undergoes malignant transformation, thus the most common tumor is chondrosarcoma.
What is an important characteristic of osteochondroma?
Always point away from the joint they are closest to
What is the condition when patient has multiple osteochondromas?
Hereditary multiple exostosis
What is the old name for this condition?
Diaphyseal aclasis
How is hereditary multiple exostosis inherited?
Autosomal dominant
What are the common bones affected in HME?
1) Long bones


2) Scapula


3) Pelvis


4) Ribs
Remember, makes sense that both pelvis and scapula affected, because both are limb girdles.
What radiographic finding is seen in 30% of people with HME?
Bayonet hand
What is Bayonet hand?
Shortening of the ulna due to involvement with an osteochondroma results in change in axis of the wrist, with angulation of the articular surface of the radius (image 74-47).
What percent of patients with HME will have malignant transformation of a lesion over their lifetime?
5%
When do osteochondromas stop growing?
When the person starts growing.
Why?
The hyaline cartilage cap is similar in histology to a physis, and acts the same way.
What is the first sign of malignant transformation?
Growth of a previously stable lesion after bone maturity.
How is malignant transformation assessed on imaging?
Evaluate the hyaline cartilage cap
What modalities can be used?
MRI, US or CT
What thickness of cartilage cap is definitely abnormal?
2 cm or greater
What thickness is suspicious and needs to be watched closely?
Anything over 1 cm
What are other signs of malignant tranformation of an osteochondroma?
1) Invasion or destruction of the bone beneath the cartilage cap


2) Matrix calcification within the cartilage cap (or extending out of it)
What does the matrix calcification look like and what does it signify?
It looks like cartilaginous matrix (rings, arcs) and occurs because the chondrosarcoma that has formed there is producing matrix. It is NOT a sign of lesion resolution.
What is the fourth most common primary cartilage tumor?
Chondroblastoma
What is the peak age?
20
Where does it occur especially?
Like many, around the knees and the proximal humerus.
What is chondroblastoma famous for?
It is one of the END OF BONE LESIONS
Where in the bone do they occur?
Epiphysis
What does chondroblastoma sometimes do?
Cross the physis
What is true in these cases?
The majority of the lesion will still be located in the epiphysis
What is the appearance of the rim of the lesion?
As with any cartilaginous lesion, there is a sclerotic rim
What is the appearance of the matrix?
Variable. When you see chondroid matrix, it makes the diagnosis of chondroblastoma easy. But many chondroblastomas have no radiographically detectable matrix calcification.
What is the clinical presentation of chondroblastoma?
It has an inflammatory presentation. Patients are in pain.
Because of the inflammatory nature of chondroblastoma, what associated imaging findings are present?
1) Joint effusion due to synovitis


2) Bone marrow edema visible on MRI


3) Periosteal reaction due to periostitis, which can extend into the adjacent metaphysis and diaphysis.
What is the zone of transition?
Narrow, with sclerotic rim, like mentioned above
On MRI what is the appearance?
Variable, depending on how much matrix calcification. With a lot of matrix calcification, there can be dark signal. But one thing that is usually present is the surrounding marrow edema and synovitis.
What is the other famous end of bone lesion?
Giant cell tumor
What is its behavior?
Benign but locally aggressive
What is its position within the marrow cavity?
Just like chondroblastoma, giant cell tumor starts off eccentrically.
What is the matrix appearance of a giant cell tumor?
Purely lytic.

In fact, if there is calcification, it is NOT a giant cell tumor.
What is its zone of transition?
Narrow, but unlike chondroid lesions, there is no sclerotic rim.
What is one reason that a GCT can have sclerotic rim?
If there is an associated fracture that is healing
What would be another different appearance of GCT versus chondroblastoma, on MRI?
There is no surrounding inflammatory reaction (i.e. no marrow edema, no synovitis). (unless there is an associated fracture).
What is special about the age distribution of giant cell tumor?
It has a very narrow bell curve.
What is the average age?
32
What is always true with regards to age for GCT?
Only occurs in skeletally mature patients.
What is the least common benign cartilaginous tumor?
Chondromyxoid fibroma
What is a chondromyxoid fibroma histopathologically?
A lesion with chondroid, myxoid and fibrous matrix elements
What is the radiologic appearance of matrix in chondromyxoid fibroma?
Purely lytic, even though it has chondroid elements histologically.

If you see chondroid matrix, think of another lesion, and don't include this in your differential.
How is CMF treated?
Curettage or en-bloc excision
What is the radiographic appearance of CMF?
Lytic lesion.
Where in the bone does it occur?
Where most fibrous lesions occur, in the metadiaphysis.
What is the appearance of its borders?
Narrow zone of transition


Sclerotic rim


Scalopped borders
What is its size?
Can be very expansile
What is it associated with?
Can have ABC form within it, and the CMF can be quite expansile with or without associated ABC
What is in the differential for the appearance of CMF?
Plain ABC can appear like CMF, and is in the differential
Where does CMF occur within a segment of bone? Centrally or eccentrically?
Eccentrically
Where do these lesions have a predilection to occur?
Lower extremity long bones



Metaphyses of the hands and feet
What is a special sign suggestive of CMF?
Cortical blister sign
What is the cortical blister?
Focal elevation of the cortex, which CMF can cause.
What is the peak age of diagnosis for osteoid osteoma?
7 - 20 years
What do we look for to make the diagnosis of osteoid osteoma?
The nidus
What is the nidus?
The lucent area in the center of the lesion
What is the nidus composed of?
Highly vascularized osteoid tissue
What does this highly vascularized tissue do to the surrounding bone?
Causes an intense sclerotic reaction
What is sometimes seen within the nidus?
A central calcification (clarification--this calcification is not the nidus. The nidus is the lucent part)
What is the best modality to evaluate a suspected osteoid osteoma?
CT, to look for the lucent nidus
What other modality can be useful?
Nuclear med bone scan
What modality is not very useful?
MRI.
Why?
Marrow edema can obscure the nidus
Where can the nidus be within the bone?
Can be intramedullary, intracortical, or subperiosteal
Where are the lesions that cause the most bony sclerosis and periosteal reaction?
Subperiosteal and intracortical lesions, more than the intramedullary ones.
Where do osteoid osteomas occur most commonly?
Long tubular bones


Posterior elements of the spine


Small bones of the hands and feet


Carpal or tarsal bones
Where do most osteoid osteomas that occur in the long tubular bones occur?
Diaphysis
In diaphyseal osteoid osteomas, what area of the bone is the nidus located?
Cortical.
So what is seen?
Radiolucent lesion with surrounding bony sclerosis, cortical thickening, and subperiosteal new bone formation
How big is the nidus in osteoid osteoma?
Small. Less than 1 cm.
What is the differential diagnosis for the appearance of osteoid osteoma?
1) Stress fracture



2) Osteoblastoma
How do you differentiate from stress fracture?
The radiolucent area is usually linear, not so round or oval shaped like in osteoid osteoma.
How do you differentiate from osteoblastoma?
SIZE.

Osteoblastoma is larger
When osteoid osteoma occurs in the spine, what are the findings seen?
Scoliosis
Where on the scoliotic curvature is the osteoid osteoma located?
Concave aspect, near the apex of the curve
What structures in the posterior elements does OO usually involve?
Pedicle


Lamina


Articular process
What is required to definitively diagnose the lesion, usually?
CT to identify the nidus
How does osteoid osteoma often present when it occurs in the metacarpals or other tubular bone of the hands and feet?
Presents with symptoms and appearance like osteomyelitis, with soft tissue swelling and bony lucency. May have an especially sclerotic rim to help differentiate it
In what bones does osteoid osteoma tend to have its nidus in the medullary cavity?
When it occurs in the:

1) Epiphyses of long bones


2) Carpal and tarsal bones
What is the presentation of osteoid osteoma when it occurs within the boundaries of a joint capsule?
Mimics inflammatory arthritis
How does the imaging appearance differ from osteoid osteoma elsewhere?
No periosteal reaction, because there is no periosteum within the joint capsule, just a loose perichondrium which doesn't exhibit reaction.


No significant bony sclerosis occurs. But there is synovitis with joint effusion.
What can intraarticular osteoid osteoma lead to?
Irreversible intraarticular cartilage and bone damage.
What is the scintigraphic appearance of osteoid osteoma?
Central area of markedly increased uptake, corresponding to the nidus, with surrounding area of slightly increased uptake.
How is osteoid osteoma treated?
Surgical resection of the entire nidus.

I think the nidus is now sometimes ablated.


Sometimes they burn themselves out.
So, what is the only thing you must see radiographically to suspect osteoid osteoma?
A lytic/lucent lesion, OR a sclerotic lesion.
What is a lesion that is histologically identical to osteoid osteoma?
Osteoblastoma
What are the differences?
1) Larger nidus


2) Typically less pain
Where do they occur?
40% in vertebrae and flat bones


35% Long tubular bones


15% Skull, maxilla, or mandible

10% Short tubular bones of hands/feet
What is the peak age for osteoblastoma?
Second and third decades
Do they look like osteoid osteomas?
No, they really dont. They have mixed lytic and sclerotic appearance and are expansile. (74-11)
Are all osteoblastomas benign?
There is an aggressive subtype which behaves locally aggressive, and can in fact kill the patient.
What is the the most common primary malignant neoplasm of bone?
Myeloma
What is the second most common malignant neoplasm of bone?
Osteosarcoma
What percent of osteosarcoma is conventional variety?
80%
What is the median age of presentation?
17
What bones are most commonly involved?
Long tubular bones
Where in the bone do they occur?
Metaphysis. But 20% extend into the diaphysis and/or epiphysis, and 75% show histologic invasion of the physis.
What specific sites are most common?
1) Distal femur


2) Proximal tibia


3) Proximal humerus


4) Distal tibia
What percent have pulmonary metastasis at the time of diagnosis?
20%
What is the treatment?
Preoperative chemotherapy followed by local resection and limb salvage if possible.

Postop chemotherapy may also be used.
What is the matrix appearance of osteosarcoma?
1/4 purely lytic


1/4 purely sclerotic


1/2 mixed
What is typical appearance of periosteal reaction?
2 forms seen
What is the first one?
Sunburst appearance, with radiating spicules of new bone.
What is this similar to?
Hair on end appearance, where spicules are just perpendicular to bone, not radiating out from a central area.
What is hair on end appearance seen in?
Classic for Ewing sarcoma
What is the other appearance of periosteum in osteosarcoma?
Elevation of the periosteum by tumor that has broken through the cortex, but which uplifts and causes subsequent periosteal reaction only on one side (i.e. proximal or distal) to the breakthrough.
What does this look like on x-ray?
A sclerotic triangle just on the bony surface.
What is this appearance called?
Codman's triangle
What is special about the demographics of parosteal osteosarcoma?
Older patient population--median age of 20s to early 30s
What is different about their behavior?
Locally aggressive only, tend not to metastasize.
How are they treated?
Wide en-bloc excision
What happens if they recur?
They tend to occupy the medullary cavity the second time around.
What does this mean for the patient?
Once it involves the medullary cavity, they do not have different prognosis than conventional osteosarcoma.
So basically, what is the difference between parosteal and conventional osteosarcoma?
Parosteal is a cortical lesion.
How can it appear?
Can just be a sessile outgrowth, but it commonly wraps itself around the bone.
What is in the differential for the appearance of parosteal osteosarcoma?
Heterotopic bone formation
What is this called in other terms?
Myositis ossificans
How is myositis ossificans differentiated from parosteal osteosarcoma?
Pattern of ossification
How does myositis ossificans ossify?
The periphery of the myositis ossificans lesion ossifies first, progressing centrally (i.e. towards the bone)
How does parosteal sarcoma ossify?
From the center (i.e. base of the lesion, on the parent bone) towards the periphery.
What is a very rare form of osteosarcoma?
Periosteal osteosarcoma
How do you evaluate surface osteosarcomas (parosteal and periosteal)?
Need to do cross sectional imaging to verify that the medullary cavity is spared. If it is, then the lesions will have a better prognosis than conventional osteosarcoma.
What are the other ossific malignant tumors?
None. All are variants of osteosarcoma.
What is the malignant cartilaginous tumor?
Primary intramedullary chondrosarcoma
What is the average age?
52
What is the clinical presentation?
Indolent. Not as dramatic as osteosarcoma. Months of progressively increasing pain.
What is the doubling time of primary chondrosarcoma?
200 days
What is the significance of this?
Important with respect to follow up imaging. You have to realize that the lesion has a long doubling time. If you bring patient back for repeat imaging in 1 month, or even 3 months, there may not be much of a difference in the appearance of the lesion, and you might incorrectly assume that it doesnt need to be biopsied.
Why do you keep calling it PRIMARY chondrosarcoma?
To differentiate it from chondrosarcomas that arise in a precursor lesion.
What is the big problem in the diagnosis of chondrosarcoma?
The decision of whether a lesion is still an enchondroma versus whether it has crossed the line and is a chondrosarcoma.
Why is this such a difficult dilemma?
Because you cant just go and stick a needle into something that you think might be a chondrosarcoma.
Why?
Because a chondrosarcoma gets mad when a needle gets stuck into it, and this previously indolent lesion can now start spreading through the soft tissues, and behave like a completely different animal.
What is the best feature that helps you differentiate enchondroma from chondrosarcoma?
1) There should not be expansion of the long tubular bones with enchondroma (expansion is commonly seen in the short tubular bones, but not in the long tubular bones).
What is another helpful fact about malignant transformation of enchondroma?
Malignant transformation of a solitary enchondroma of the small bones of the hands or feet is very uncommon.
What are some other features of enchondroma, which when seen should cause you to be suspicious of malignant transformation into chondrosarcoma?
Enlarging radiolucent area


Soft tissue mass


Disappearance of preexisting calcification


Pathologic fracture
What is a lesion that is a gray zone between enchondroma and chondrosarcoma?
Low grade chondrosarcoma.
What is the behavior of these lesions?
Very indolent
How are suspected low grade chondrosarcomas treated?
Usually just observed
Can a chondrosarcoma become more malignant?
Yes
What is this process called?
Dedifferentiation of chondrosarcoma
In what percent does this occur?
10% of primary and secondary chondrosarcomas
What actually is occurring in dedifferentiation of chondrosarcoma?
You still have the same chondrosarcoma there, but now side by side with it, you have another more malignant cell type.
What type of lesion is this typically?
Malignant fibrous histiocytoma
What is the average age for dedifferentiated chondrosarcoma?
a decade older, 62.
We talked earlier about end of bone lesions: Chondroblastoma and giant cell tumor. What is a chondroid malignant tumor that is also an end of bone lesion?
Clear cell chondrosarcoma
Is this a common or uncommon lesion?
Very uncommon
What percent of chondrosarcomas does it represent?
only 1%
What makes it different than regular chondrosarcoma otherwise?
Much younger population; average age 35
What sites is the clear cell chondrosarcoma most commonly seen at?
1) Proximal femoral epiphysis



2) Proximal humeral epiphysis


3) Pelvis
If you had to pick a chondrosarcoma, which one would be best?
Clear cell. Because it is very indolent.
How is it treated?
Just like parosteal osteosarcoma, with wide en-bloc excision, but since it is in a joint, more complicated.
What appearances characterize a low grade chondrosarcoma?
Well organized rings in the matrix
What appearance may suggest higher grade lesion?
1) Large areas of noncalcified matrix (due to the presence of dedifferentiation with MFH)


2) Irregular calcifications in the matrix.


3) Wide zone of transition.
What is the appearance of the matrix in clear cell chondrosarcoma?
Predominantly lytic
What do they do to the structure of the bone?
Slightly expand it
What characterizes the zone of transition
Variable. May be wide or narrow with sclerotic margin
What is the appearance of a clear cell chondrosarcoma identical to?
Chondroblastoma. Thus when you say one in your differential, the next thing out of your mouth should be the other.
What features favor clear cell chondrosarcoma over chondroblastoma?
Presence of metaphyseal involvement


Absence of periostitis
What other lesions are in the differential diagnosis for clear cell chondrosarcoma?
Aneurysmal bone cyst


Osteoblastoma


Giant cell tumor


Brown tumor of hyperparathyroidism


Mets


Plasmacytoma (myeloma)
What is a cartilage forming tumor that can arise in either bone or SOFT TISSUE?
Mesenchymal chondrosarcoma
What is its behaviour like?
Very aggressive
What percent of malignant cartilage tumors does it represent?
only 1.5%
How does it present?
Large lytic lesions


Usually widespread metastases
What bones does it involve?
Very widespread involvement. The three most common sites are femur, ribs and spine, but all these combined only comprise 35% of all mesenchymal chondrosarcoma.
What is the most common primary malignant tumor of bone?
Multiple myeloma
What can myeloma not be distinguished from?
Metastases. That's why we say them in the same breath.
What is the age distribution?
40-80
What is the typical radiographic appearance? (for boards)
Multiple discrete lytic lesions
What is a common appearance in the real world?
Generalized osteopenia
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