Bone tumors part one

CHONDROID TUMORS
Cartilage tumours represent a wide spectrum of entities ranging from
lesions that are more like hamartomas than neoplasms to highly
aggressive sarcomatous tumours.
There is a gradual transition between benign and low-grade
malignant chondrogenic tumours, making differential diagnosis and
treatment decisions difficult and leading to an especially important
role of radiology.
Like other primary bone tumours, most chondrogenic tumours have a
certain predilection for the age and site of manifestation

key facts:
Typical presentation: well-defined osteolytic
lesion in tarsal bone, patella or epiphysis of a
long bone in a 20-year old with pain and
swelling in a joint.
Abundant edema is almost always present.
DD: Ganglion cyst, osteomyelitis, GCT, ABC,
enchondroma.
The lesion can be lobulated, usually with a
sclerotic margin.
Frequently a regular benign periosteal
reaction is present.
MR imaging usually shows prominent bone
marrow and soft tissue edema.
The differential diagnosis of an epiphyseal
lesion in young patients, besides
chondroblastoma, includes osteomyelitis and
ganglion cyst.
In the foot the differential diagnosis is longer.

Chondroblastoma
There is a well-defined lytic lesion located
posteriorly in the proximal epiphysis of the
tibia.
On the radiograph there is some reactive
sclerosis surrounding the lesion.
There is no matrix formation.
On the coronal T2-weighted image with fat
suppression the lesion has a high SI and
subtle internal ridges.
There is edema of the entire epiphysis.
On a sagittal T1-weighted image there is a
discrete sclerotic margin.

Degenerative cyst
Here a patient with arthrosis of the knee and
a large well-defined osteolytic lesion in the
epiphysis of the tibia.
In young patients the differential diagnosis
would include chondroblastoma, intraosseous
ganglion and giant cell tumor.
In this elderly patient with arthrosis this
lesion is most probably a degenerative cyst.

Chondroblastoma
The talar or calcaneal bone is one of the
predilectional sites of chondroblastoma.
Note the thin sclerotic margin and
surrounding edema.
Other diagnostic possibilities in the young
population: SBC (no edema), ABC (fluid
levels), or osteoblastoma.

Chondroblastoma
Here a lesion located in the epi- and
metaphysis of the proximal humerus.
The lesion is predominantly calcified.
Coronal T1W image shows lobulated margins
and peripheral low SI due to the
calcifications.
Notice the surrounding decreased signal
intensity of the bone marrow, consistent with
edema.
Edema almost always accompanies
chondroblastoma, but is unusual in other
chondroid tumors, like enchondroma or low-
grade chondrosarcoma.

Chondroblastoma
On the left an eccentric well-defined lytic
lesion in the proximal femur.
CT image shows a lobulated and sclerotic
border.
The location in the epiphysis is typical for a
chondroblastoma.

Same patient.
Coronal T2-WI with FS demonstrates high SI
of the lesion with a low intensity sclerotic
border with perilesional edema.

Edema is almost always present in
chondroblastoma.
Here some examples:
1- Typical chondroblastoma with epiphyseal
localization. Some reactive sclerosis and
abundant perilesional edema on T2-weighted
image with fat saturation.
2- Coronal T2-weighted image with fat
saturation demonstratesa chondroblastoma in
the femur epiphysis with perilesional edema
(same case as above).
3- Sagittal T1-weighted MR image of a lytic
lesion with peripheral sclerotic rim in the
posterior talar bone in a young patient.
The lesion is hypointense, well-defined with a
low intensity rim.
The bone marrow has a low signal intensity
due to extensive edema (arrow).

Chondroblastoma
The images show a chondroblastoma in the
patella.
Notice the extensive edema (blue arrow)

Chondroblastoma
Here lesion in the proximal tibia in a 20 year
old.
Key findings:
- Epiphyseal lesion
- Lobulated margins
- Extensive edema
- Young patient.
Diagnosis: Chondroblastoma.
Diff. diagnosis: Osteomyelitis.

Chondroblastoma
What are the findings:
- Well-defined osteolytic lesion in the
talus.
- No matrix formation.
- Subtle reactive sclerosis.
- T2-WI with FS shows typical extensive
peritumoral edema in the entire bone.
- High uptake on bone scintigraphy.
Diagnosis: Chondroblastoma.
The talar bone is one of the preferential
sites for chondroblastoma.

DDX
Localisation is a key point in the differential diagnosis of
chondroblastoma as only a few other lesions share this predilection
site.
 Giant cell tumours
 are located metaepiphyseally, are more aggressive in terms of cortex penetration and prefer a slightly
older age group.
 Bone abscesses
 have a wider sclerotic rim, but can occur in a metaepiphyseal location and produce a profound perifocal
oedema as well.
 Metastases
 predominantly occur in a much older age group.
 Ganglia,
 frequently located in the epiphyseal area of long bones, do not show matrix mineralisation, are more
frequent in higher age groups and can mostly be distinguished by the fluid signal they show on MR
imaging.

DDX
 Clear cell carcinoma,
 a rare low-grade malignant lesion that can be morphologically indistinguishable from chondroblastoma.
Its peak manifestation age is slightly higher than that of chondroblastoma, but age distribution
overlaps widely. Its most frequent localisation is the proximal epiphysis of the femur, a site that is
infrequent in chondroblastoma.
 Chondromyxoid fibromas
 usually arise in the metaphysis. If they extend into the epiphysis differentiation from a
chondroblastoma with extension into the metaphysis can be difficult.
 A fibrous dysplasia
 can be diagnosed by its ground-glass density, if not radiographically then on computed
tomography. In contrast to chondroblastoma it usually shows little perifocal reaction on MR
imaging.

CHONDROMYXOID FIBROMA
CMF is a rare benign osteolytic lobulated lesion preferentially found
eccentric in the tibia metaphysis and less common in the femur and
foot.
Mainly found in young adults.
The lesion may cause cortical expansion.
Calcifications are usually not present.
 show only little periosteal reaction. Occasionally, matrix calcifications can be seen
in a punctuate, flocculent or rings and arcs pattern
Bony ridges that seem to transverse the lesion are frequent
Differential diagnosis: ABC, NOF and fibrous dysplasia.

Chondromyxoid fibroma
Eccentric well-defined lytic lesion in the
metaphysis of the proximal tibia in a
young child.
Contours are somewhat lobulated,
narrow transitional zone.
Differential diagnosis, because of the
eccentric manifestation: non-ossifying
fibroma or chondromyxoid fibroma.
Axial T2-weighted image nicely shows
the low SI sclerotic margin, high SI of
the intrinsic part of the lesion, bone
marrow edema and some soft tissue
reaction.
There is thick peripheral enhancement
on sagittal T1-weighted after Gd-
DTPA.
The MR features support the diagnosis
of CMF

On the left a well-defined lytic lesion at
the base of the 2nd metatarsal bone.
There is no mineralisation.
T1-weighted images before and after
Gd-DTPA demonstrate some expansion
and lobulation.
On the T1-weighted image before
contrast there is a nonspecific
intermediate signal intensity.
After the administration of Gadolinium
there is thick peripheral enhancement.
Differential diagnosis based on plain
radiograph: giant cell tumor or
chondroid lesion, i.e. enchondroma,
low grade chondrosarcoma or CMF.
Biopsy revealed CMF.
Although this is a rare lesion, the foot
is one of the preferential sites of origin.

On the left a diaphyseal cortically
based lytic lesion with expansion and a
thin peripheral bone shell.
There is peripheral enhancement on
the axial T1-weighted image with fat
saturation.
The lobulated morphology with high SI
on the T2-weighted image with fat
saturation suggests that this is a
cartilaginous lesion.

DIFFERENTIAL DIAGNOSIS
Juvenile and aneurysmal bone cysts,
 Matrix calcifications detected radiographically or by computed tomography exclude
these entities.
 MR imaging is able to differentiate a solid lesion like a chondromyxoid fibroma
from these cystic lesions
Giant cell tumour
 more likely to reach the subchondral bone in the epiphysis and more
 frequently penetrates the cortex without neocortex formation.
 the presence of uniform mineralization throughout large parts of the lesion is
inconsistent with giant cell tumour.

Enchondroma of the long bones
 Is typically located centrally and mostly does not affect the cortex. Enchondroma in
the short bones is much more frequent than chondromyxoid broma but can show a
similar radiographic pattern.
Non-ossifying fibroma
 is usually asymptomatic, as long as no complicating pathologic fracture occurs.
 In particular, larger non-ossifying fibromas can be radiographically
indistinguishable from chondromyxoid fibroma.
Fibrous dysplasia
 can show a typical ground-glass pattern which is pathognomonic.
 In contrast to chondromyxoid fibroma, it is usually an asymptomatic lesion.
Polyostotic involvement as found in fibrous dysplasia is not described in
chondromyxoid fibroma.

Eosinophilic granuloma
 is usually more aggressive than chondromyxoid fibroma,
 shows some periosteal reaction and frequently lacks a thin and uniform sclerotic
rim.
 Furthermore, it shows significant perifocal reaction in MR imaging

ENCHONDROMA
Well-defined osteolytic cartilage-forming lesion, most commonly encounterered
centrally in the phalanges of hands and feet.
Other common locations: femur, humerus and metacarpals.
Must have calcifications except in phalanges.
May show mild expansion, but endosteal scalloping is not allowed for the
diagnosis.
Enchondromas may have an eccentric origin.
Pain and periostitis is sign of malignancy, i.e.chondrosarcoma.
On MR enchondromas show lobulated contours, very high signal intensity on T2-
weighted images with fat suppression. The enhancement pattern is peripheral or
septal-nodular. Dynamic enhancement should not be rapidly progressive unlike
in chondrosarcoma.
Uptake on bone scan usually low or absent

Left:
Well-defined lytic lesion with sclerotic
margin and some expansion. There are
fine calcifications.
This patient presented with a fracture,
which is a common first presentation of
an enchondroma.
Middle:
Well-defined lytic lesion without a
sclerotic border also with a fracture.
Right:
Lesion with irregular cortical bone
destruction. Low-grade chondrosarcoma
has to be included in the differential
diagnosis, but is uncommon at this
specific location.

Enchondroma
Lytic lesion within the phalanx with
irregular cortical bone destruction and
soft tissue extension should raise the
suspicion of a chondrosarcoma.
A lytic lesion within a metacarpal bone
with expansion with or without
calcifications, with or without cortical
bone destruction is not infrequently due
to chondrosarcoma.

Enchondroma
On the left another enchondroma.
here is a well-defined eccentric
osteolytic lesion.
The location is typical for enchondroma.
Notice the lack of calcifications.

Enchondroma
On the left a well-defined lytic lesion
with some expansion of the rib.
The differential diagnosis based on the
radiograph is: fibrous dysplasia,
enchondroma, and less likely
eosinophilic granuloma or hemangioma.
The coronal T1-WI after Gd with fatsat
shows a lobulated lesion with peripheral
enhancement consistent with the
diagnosis of an enchondroma.

Multiple enchondromas
Multiple enchondromatosis is known as
Ollier's disease.
Multiple enchondromas and
hemangiomas of soft tissue are known
as Maffucci's syndrome.
In both conditions there is a 30% risk of
malignant transformation.
Enchondroma
On the left a patient with multiple
eccentric lytic lesions in the metacarpal
bones and phalanges of the left hand.
On T2-WI with FS there is homogeneous
high SI of the lesions.

On the left another patient with multiple
well-defined lytic lesions in a central and
eccentric localisation in the phalanges.
On the right the MR of a different patient
with multiple lobulated chondroid
lesions with high SI on T2-WI with fatsat.

ENCHONDROMA
Enchondromas of the long tubular bones may have two different
radiographic patterns
 dense chondrogenic calcications completely obscuring the underlying destruction
and typically showing no sclerotic rim
 sharply demarcated lytic lesions with a thin rim of sclerosis and a varying degree of
chondrogenic or amorphous calcication. Within the long bones they may occur in an
eccentric location and have a slightly expansile pattern of bone destruction with
formation of a thin neocortex

Here a well-defined osteolytic lesion in
the proximal ulna.
There is no mineralisaton.
Differential diagnosis: ABC, GCT, fibrous
dysplasia.
Despite the lack of calcifications the final
diagnosis was enchondroma.

DDX
low-grade chondrosarcoma
differential diagnoses of densely calcified enchondromas
 may be sclerotic lesions of any kind. These can normally be separated very well as
they lack the typical chondrogenic pattern of calcification.
 Metaphyseal bone infarcts, however, can resemble densely calcified enchondromas
radiographically.
differential diagnosis of lytic forms of enchondroma comprises
 fibrous dysplasia and non-ossifying fibroma.
 Within the chondrogenic tumours, chondromyxoid fibroma and chondroblastoma
rarely can be differential diagnoses for atypical cases of enchondroma

OSTEOCHONDROMA
Bony protrusion covered by a cartilaginous cap.
Growth in childhood takes place in the cap, corresponding to normal enchondral growth
at the growth plates.
A thick cartilaginous cap in an adult is suspicious of chondrosarcoma.
Osteochondroma usually presents as an incidental finding, or in the form of a syndrome
with multiple osteochondromas.
Radiographically, osteochondromas usually are located at the metaphysis of long bones
and directed away from the joint, or arise from flat bones like the scapula or pelvis.
Typically, the underlying cortical bone extends into the stalk of the lesion, which can be
thin or broad-based.
On MR imaging, the central part of a mature osteochondroma consists of fatty bone
marrow, continuously with the marrow cavity of the underlying bone.
On the outside a thin cartilaginous cap may be present and focal areas of enchondral
ossification, just beneath the cartilage cap.
In the mature phase, the osteochondroma is typically homogeneously sclerotic and well-
defined.

A patient with a broad-based
osteochondroma.
Notice that the cortical bone extends
into the lesion.
This feature differentiates it from a
juxtacortical tumor.

Here a bony protrusion arising from the scapula
with the cortex extending in a mixed sclerotic
mass.
The MR image shows a thin peripheral cartilage
cap.
The osteochondroma consists for the larger part
of bone marrow with focal sclerosis

MALIGNANT TRANSFORMATION
Radiographic features that should raise the suspicion of malignant
transformation on plain radiographs or CT include:
 Growth of osteochondroma in skeletally mature patient
 Irregular or indistinct surface of lesions
 focal lucent regions in interior of lesions
 erosion or destruction of adjacent bone
 presence of soft tissue mass with scattered or irregular calcifications
risk of malignant transformation of solitary osteochondromas is very low and
almost always seen in skeletally mature patients.
 Atypical location in the skeleton, large size and broad-based morphology are risk
factors.
 In particular, secondary chondrosarcomas of the pelvis, scapula and thigh can get very
large.

a patient with multiple
osteochondromas.
Follow up is necessary because of an
increased risk of malignant
degeneration.

CT:
Large osteochondroma arising from the
iliac bone.
The central defect and punctate
calcifications are highly suspicious for
malignant progression to a peripheral
chondrosarcoma.
MRI:
The defect is filled with a large cartilage
cap with high SI.
This is diagnostic for the diagnosis
chondrosarcoma

Here a patient with a large calcified mass
arising from the proximal fibula.
There is high uptake on a bone scan.
The axial T1-weighted MR image
demonstrates a large lobulated mass
enveloping the fibula and the stalk of a
previous osteochondroma in continuity
with the bone marrow compartment.
All these findings indicate
chondrasarcoma arising from an
osteochondroma.

Osteochondromatosis (hereditary
multiple exostosis, HME) is an autosomal
dominant inherited trait with an
incidence of at least one in 50,000
About 75% have a clinically apparent
deformity and about 40% have a short
stature.
Lesion size and number of lesions are
the most relevant factors for the risk of
malignant transformation.
The rate of malignant transformation is
reported to be in the range of 5–25% of
patients

CHONDROSARCOMA
Malignant bone tumor that produces cartilage.
Typical presentation: large osteolytic lesion with scalloping of the inner
cortex and rings-and-arcs or popcorn calcifications in an elderly person with
a painful swelling.
Secundary chondrosarcoma is most common and arises from enchondroma
or osteochondroma.
Patients with multiple enchondromas like in Ollier's disease and Mafucci's
syndrome are at risk.
Low grade tumor can usually not be differentiated from enchondroma based
on imaging findings alone.
High grade tumor may present as aggressive ill-defined lesion with
extention into the soft tissues.

CHONDROSARCOMA
On plain radiographs the differential diagnosis with enchondroma can
be difficult.
Think of chondrosarcoma instead of enchondroma if there is one or
more of the following features:
 Elderly patient
 Location in long bones
 Size > 5 cm
 Uptake on bone scan
 Endosteal scalloping on MRI
 Cortical involvement
 Early enhancement on dynamic contrast enhanced series

Chondrosarcoma
The differential diagnosis on the plain
radiographs in all these three cases is
enchondroma.
Additional MR imaging and bone
scintigraphy may be helpful to make the
diagnosis of chondrosarcoma more or
less likely.

Chondrosarcoma
On the left a massive chondrosarcoma of
the skull base with extension to the
nasal and paranasal cavities and orbita.
CT demonstrates irregular calcifications
produced by the tumor.
A T1-weighted image after Gd shows
typical septal and nodular enhancement.

Chondrosarcoma
On the left a chondrosarcoma in the
proximal tibia diaphysis.
The tumor is recognized by subtle
calcifications in the proximal part.
The distal border is not well defined.
Notice endosteal scalloping at the medial
side which is a hallmark of
chondrosarcoma.
MR better defines the extension of the
lesion.
MRI also demonstrates the endosteal
scalloping.

Chondrosarcoma
Partially calcified chondroid tumor in the
proximal tibia.
Based on the imaging findings it is not
possible to differentiate between an
enchondroma or a low grade
chonrosarcoma.
On the coronal T1-weighted MR the
typical chondroid morphology is seen.
There is no evidence of endosteal
scalloping.
Continue with bone scan and dynamic
MR.

Bone scintigraphy of the same patient
shows increased uptake in the lesion.
This increased uptake in a chondroid
tumor is in favor of the diagnosis of a
low grade (grade I) chondrosarcoma.
The fast dynamic contrast enhanced MR
image with subtraction revealed early
and progressive enhancement, which is
also in favor of the diagnosis of a grade I
chondrosarcoma.

Chondrosarcoma
On the left a patient with a calcified
lesion in the proximal diaphysis of the
tibia.
On the sagittal T1-weighted CE image.
The calcifications with low SI are present
in the proximal part.
On the MR, the lesion is far more
extensive than suspected on the plain
radiograph at first glance.
On second inspection you will notice the
subtle endosteal scalloping of the tumor
on the radiograph.
The large diameter and the scalloping
favor the diagnosis of a
chondrosarcoma.

Chondrosarcoma
On the left a patient with a
chondrosarcoma of the right
acetabulum.
On the CT expansion and subtle
calcifications are present.
On the coronal T2-weighted image the
tumor is seen as a large lobulated mass
with very high SI, which is typical for
chondroid tumors.
The T1-weighted image after Gd shows
typical peripheral nodular enhancement.
In the center there is no enhancement.
This is probably due to a large myxoid
component.

Chondrosarcoma
On the left a patient with a broad-based
osteochondroma with extension of the
cortical bone into the stalk of the lesion.
Notice the lytic peripheral part with
subtle calcifications.
This part corresponds to a zone of high
SI on T2-WI with FS on the right.
This represents a thick cartilage cap.
This is an example of progression of an
osteochondroma to a peripheral
chondrosarcoma.

On the left a typical broad-based
osteochondroma arising from the
proximal humerus.
The major part of the bony protrusion
consists of fatty bone marrow.
There is a thin peripheral cartilage cap,
i.e. no suspicion for malignant
degeneration.

Chondrosarcoma
On the radiograph there is only a vague
sclerotic lesion.
The sagittal T2-WI FS much better
demonstrates the presence and
extension of a lesion with lobulated
margins and a mixed pattern of high and
low SI. Calcificatons contribute to the low
SI within the tumor.
Diff. diagnosis: enchondroma or low-
grade chondrosarcoma.
Biopsy: low grade chondrosarcoma.

Chondrosarcoma
Here a lesion consisting of rings-and-
arcs calcifications in the proximal
humerus.
The differential diagnosis is
enchondroma or low grade
chondrosarcoma.
The CT shows the calcifications with
subtle endosteal thinning of the cortical
bone (arrows).
Final diagnosis: low grade
chondrosarcoma.

Chondrosarcoma
Here a patient with a lesion in the
proximal humerus with typical popcorn
calcification.
The most likely diagnosis is
enchondroma, however progression to a
low-grade chondrosarcoma cannot be
excluded based on the plain radiograph
alone.
There is increased activity on the nuclear
bone scan, which is more in favor of the
diagnosis of a chondrosarcoma.
This proved to be a low-grade
chondrosarcoma.

Chondrosarcoma
Here a lytic ill-defined lesion in the
distal diaphysis of the femur in an old
patient.
Notice the cortical thickening, but also
endosteal scalloping (blue arrow).
The differential diagnosis should include
metastasis and myeloma.
At closer look, there are also faint
calcifications present (arrowhead).
The T1WI+Gd with fatsat demonstrates
the presence of a solid enhancing part
and perilesional edema.
In combination with the ill-defined
appearance on the plain radiograph this
suggest that this is a high grade
chondrosarcoma.

Here a lobulated lytic lesion of the
proximal humerus.
The presence of calcifications suggest a
chondroid tumor.
The lytic parts with cortical involvement
and expansion raise the suspicon of a
high grade chondrosarcoma.
Diagnosis: high grade chondrosarcoma

Chest X-ray shows non-specific soft
tissue mass in the right lower lobe.
CT shows the mass extending from the
posterior chest wall, with irregular
calcifications, consistent with
chondrosarcoma.
Diagnosis: high grade chondrosarcoma.

DDX
Differential diagnosis depends on the detection of chondrogenic
calcifications.
 If these can be identified ensuring that the lesion is a chondrogenic tumour, the
main differential diagnosis is that of an enchondroma.
 If no chondrogenic calcifications are seen, a larger group of tumours of the higher
age group has to be included in the differential diagnosis, e.g. metastasis,
malignant fibrous histiocytoma, fibrosarcoma or lytic secondary osteosarcoma

ENCHONDROMA VS.
CHONDROSARCOMA
Lesion-related pain, especially when not explained by the mechanical situation of the parent bone, i.e. if the lesion is not likely
to cause a stress phenomenon.
Clinical differentiation, e.g. involving the application of local anaesthetics to nearby joints to exclude
joint-related pain, may be helpful
Atypical localisation.
Large lesion size, e.g. larger than 5 cm.
Any radiographic change in the mature skeleton.
Penetration of the cortex.
Deep cortical scalloping, more than two thirds of the cortical thickness.
Periosteal reaction or cortical remodelling, except for a thin neocortex.
Different calcification patterns within a lesion
Different signal patterns within a lesion in MR imaging.
Soft tissue extension.
Marked uptake of radionuclide (greater than the anterior iliac crest).

OSTEOID TUMORS
Osseous tumors are defined by the World Health Organization (WHO)
as neoplasms that produce an osseous matrix. These lesions are
divided into benign and malignant on the basis of their biological
behavior

BONE ISLAND (ENOSTOSIS)
A bone island consists of well-differentiated mature compact bone
tissue within the marrow, also referred to as enostosis.
Usually it is seen as a coincidental finding.
In patients with breast- or prostate cancer a bone island can be
mistaken for an osteoblastic metastasis.
A bone island normally does not show increased uptake on a bone
scan.
Lesions are round to oval, with the long axis of oval lesions
paralleling the long axis of the affected bone
The surrounding cancellous bone which blends imperceptibly with the
surface of the lesion provides a “brush-like” margin

Bone island
On the left a well-defined compact
sclerotic lesion in the proximal
humerus.
Most likely diagnosis: bone island or
enostosis.
In patient with a known malignancy
consider: osteoblastic metastasis.

OSTEOMA
rare lesion composed entirely of osteoid tissue, representing a focal
exaggeration of intramembranous bone formation, and accordingly,
is identified in areas associated with periosteum.
It is typically found within the paranasal sinuses and the skull, but
may rarely be identified in a long bone.
Osteomas are found in both children and adults and may be
associated with Gardner syndrome

OSTEOID OSTEMOA
Typical: lucent nidus with central small sclerotic focus
Femur, tibia, hands and feet, spine (arch).
Usually prominent periosteal and endosteal reaction (may obscure
nidus)
Axial imaging for differentiation from Brodie abscess, osteoblastoma,
stress fracture

The x-ray demonstrates an eccentric
lytic lesion in the proximal femur in a
child.
There is surrounding reactive sclerosis.
Histology revealed osteoid osteoma.
Osteoid osteoma may present as a lytic
lesion.

Here images of a male patient, 18 years
of age, with complaints of pain,
particularly at night in the fourth digit.
Plain radiograph shows extensive
sclerosis and broadening of the
proximal phalanx.
CT shows a small lucency with central
calcification and extensive sclerosis of
the bone marrow.
Scintigraphy reveals intense focal
activity.
The CT findings are pathognomonic for
an osteoid osteoma.

Axial T1 weighted TSE images before
and after Gd-DTPA of the same patient.
The nidus with the central calcification
is well seen.
Notice the enhancement of the nidus
and surrounding bone marrow due to
edema, which almost always present.

Here a typical osteoid osteoma in the femur.
Notice the extensive cortical broadening and
bone marrow edema.

Here a typical osteoid osteoma in the
tibia.

X-ray an CT-image of a typical osteoid
osteoma in the proximal tibia.
Notice the sclerotic center within the
osteolytic lesion (red arrow).

MR-images of the same patient
demonstrate cortical thickening and
extensive edema.

OSTEOBLASTOMA
Very rare lesion.
Think of osteoblastoma when a lesion looks like a large osteoid
osteoma or an ABC.
Most common location: posterior arch of vertebral body.
Osteoblastomas are lytic lesions.
Frequently however there is associated reactive sclerosis and varying
amounts of ossifications .

CT image of lytic lesion with central
mineralisation in the right acetabulum.
T2-weighted coronal MR image shows
abundant osseous edema surrounding the
lesion: osteoblastoma.
The differential diagnosis includes a
chondroblastoma.

OSTEOMYELITIS
Osteomyelitis should be included in the differential diagnosis of any
lytic lesion in any location in any age-group.
May appear highly aggressive with permeative change, periosteal
reaction and abscesses
Often reactive sclerosis
Bone defect can be found on both sides of the growth plate.
MR: cortical breakthrough with abscesses, fascial fluid
May not be able to differentiate from aggressive tumor

DDX
Since osteomyelitis can mimic almost any bone tumor or tumor-like lesion in all
age groups, the differential diagnosis is very large.
Bone tumors:
 Ewing
 Osteosarcoma
 Lymphoma
 Osteoid osteoma
 Chondroblastoma
 Leukemia
Tumor-like lesions or reactive processes
 Eosinophilic granuloma
 Intraosseous ganglion and synovial cyst
 Stress fracture
 Tug lesion
 Bone infarct

a patient with an eccentric lytic lesion in
the metaphysis of the proximal fibula.
Coronal T1WI and T1WI with Gd and fatsat
demonstrate the extension of the lesion
on both sides of the physeal plate.
There is rim enhancement and edema in
the bone marrow and soft tissues.

Brodie abscess
A Brodie abscess is a subacute osteomyelitis,
which may persist for years before converting
to a frank osteomyelitis. Brodie abscess
present as an osteolytic bone defect with
sharp borders surrounded by extensive
reactive sclerosis.
The radiograph demonstrates an ill-defined
osteolytic lesion in the tibia with extensive
reactive sclerosis and solid periosteal
reaction.
The T1WI+Gd+FS shows that the lesion
extends through the physeal plate into the
epiphysis.
There is a thick rim of enhancement and
extensive reactive edema.
Final diagnosis: Brodies abscess.

The radiograph shows a well-defined
osteolytic lesion in the distal metaphysis of
the tibia with surrounding reactive sclerosis.
The coronal T1-weighted Gd-enhanced image
with fat-suppression shows a central
hypointense focus with thick enhancing zone
and peripheral low-intensity rim.
There is extensive bone marrow edema, which
enhances.
On the sagittal T1-weighted image notice the
low signal intensity rim edging the infectious
foci and the low SI of the bone marrow due to
edema.
Final diagnosis: Brodies abscess.

Another patient with a subacute
osteomyelitis or Brodie's abscess.
On the x-ray there is an ill-defined
lucent lesion on both sides of the
growth plate of the femur.
The coronal T2-weighted image with
fat-suppression reveals the high
intensity of the abscess in the epiphysis
and metaphysis and the high signal
intensity of the surrounding marrow
edema.

The images show another case of
osteomyelitis.
Notice the ill-defined osteolysis with a
permeative pattern of destruction of the
cortex and an interrupted periosteal
reaction.
In a child the differential diagnosis
includes a Ewing sarcoma and an
eosinophilic granuloma.

Here another patient with osteomyelitis.
The radiograph shows thickening of the
cortical bone and an ovoid central
lucency.
T1WI+Gd+FS also demonstrates cortical
thickening with extensive enhancement
of the bone marrow and rim-enhanced
fluid collection centrally consistent with
an abscess.

Here another case of osteomyelitis.
There is cortical thickening, sclerosis and
a layered periosteal reaction.
Axial T2-weighted fat-suppressed image
shows high signal of the bone marrow,
cortex and surrounding periosteum.
Differential diagnosis:
Eosinophilic granuloma in a young
patient.
Ewing sarcoma especially if there was an
interrupted periosteal reaction and a
more extensive soft tissue mass.

Here two patients with quite similsr
findings on the radiographs.
Both have small osteolytic areas
surrounded by sclerosis.

OSTEOSARCOMA
Most common primary malignant bone tumor.
Typical presentation - metaphyseal bone-forming lesion around the
knee in a patient 10-25 years of age, who presents with a painful
mass.
Small second peak in > 60 years.

OSTEOSARCOMA
In 2002, the WHO Committee for the Classification of Bone Tumors
divided malignant osteogenic tumors into eight distinct diagnoses:
 (1) conventional osteosarcoma;
 (2) telangiectatic osteosarcoma;
 (3) small cell osteosarcoma;
 (4) low grade central osteosarcoma;
 (5) secondary osteosarcoma;
 (6) parosteal osteosarcoma;
 (7) periosteal osteosarcoma;
 and (8) high grade surface osteosarcoma

OSTOSARCOMA
malignant osseous lesions are grouped into three major categories which are
subsequently further divided. is categorization includes:
1. Intramedullary osteosarcoma: Lesions in this group arise within the medullary cavity
and represent the typical high grade intramedullary osteosarcoma. ey are usually
pleomorphic and produce varying amounts of cartilage and/or brous tissue, and rarely,
other histological components. While these lesions can be, and sometimes are, further
subdivided by their predominant matrix (see below), the WHO uses the umbrella term
conventional osteosarcoma for these various forms, since they have a similar biological
behavior (R et al. 2002). Additional members of this group are telangiectatic, small cell,
gnathic and low grade central osteosar coma.
2. Juxtacortical osteosarcoma: Lesions in this group are located on or in the cortex and
include parosteal, periosteal and high grade surface osteosarcoma, as well as intracortical
osteosarcoma.
3. Secondary osteosarcoma: Included in this group are lesions derived from benign
precursors, such as osteosarcoma associated with Paget disease, radiation therapy and
other benign lesions. Metastatic os teosarcoma is also included in this group, as is
osteosarcomatosis, which is now generally accepted to represent the multicentric
metastases

Study the images of a 14-year old boy
and then continue reading.
The findings are:
Radiograph.
Mixed lytic-sclerotic lesion in distal
femur metaphysis and diaphysis with
possible extension to the epiphysis.
The matrix of the tumor is bone.
Diagnosis: osteosarcoma.
MRI.
Coronal image confirms the epiphyseal
involvement with reactive edema.
Axial image shows the circumferential
soft tissue extension and relationship to
the neurovascular structures.

CONVENTIONAL OSTEOSARCOMA
Radiography
 the vast majority (approximately 90%) of osteosarcomas demonstrate a variable
amount of fluffy, cloudlike (cumulous) opacities within the lesion, characteristic of
osteoid matrix production
 a mixed pattern of sclerosis and lucent areas is most frequent.
 Conventional osteosarcoma tends to violate the cortex without expanding the
osseous contours, a characteristic that reflects its aggressive pathologic behavior.
 growth pattern is associated with an aggressive periosteal reaction (Codman
triangle, laminated, hair-on-end, or sunburst patterns) and soft tissue mass in 80–
90% of cases

CONVENTIONAL OSTEOSARCOMA
an unusual radiographic appearance can lead to delay in diagnosis
and confusion with benign disease.
 This situation is particularly likely when the osteosarcoma involves anatomically
complex areas such as the pelvis and in the case of small lesions (lesion < 5 cm
and adjacent to the endosteum).
In these cases, cross-sectional imaging may not only help confirm the
presence of the lesion, but also help identify mineralized matrix that
is not appreciable at radiography.

Here another young patient with an
osteosarcoma.
There is homogeneous sclerosis of a
large part of the right hemipelvis with
intense uptake on the bone scintigraphy.

SCINTIGRAPHY
At bone scintigraphy, marked uptake of radiotracer is seen on blood
flow, blood pool, and delayed images. Extended uptake patterns,
presumably due to hyperemia can be present
the chief role of scintigraphy is to evaluate for distant metastases

CT SCAN
primary advantage of CT scanning is its ability to demonstrate small
areas of mineralized matrix that might not be detected with
radiographs, particularly in areas in which the osseous anatomy is
complex, such as in the pelvis or spine

MRI
MR imaging has become the cross-sectional imaging modality of
choice for preoperative evaluation and staging of osteosarcoma.
Tumor is seen primarily as areas of intermediate signal intensity on
Tl-weighted images and as areas of high signal intensity, replacing
the normal marrow, on T2-weighted images.
Areas of low signal intensity on both T1- and T2-weighted MR
images are frequent and represent mineralized matrix.
Foci of central hemorrhage (which have high signal intensity with all
MR pulse sequences) and necrosis (which has low signal intensity on
T1-weighted images and high signal intensity on T2-weighted MR
images) are common in both the intraosseous and so-tissue tumor
components.

TELANGIECTATIC OSTEOSARCOMA
representing 2.5–12.0% of all lesions
is primarily (>90%) composed of multiple aneurysmally dilated
cavities that contain blood, with viable high-grade sarcomatous cells
in the peripheral rim and septations around these spaces.
may be confused with aneurysmal bone cysts
 The first imaging feature that favors the diagnosis of telangiectatic osteosarcoma
as opposed to aneurysmal bone cyst
 the detection of thick, solid or nodular tissue surrounding or associated with the cystic/hemorrhagic
spaces. This appearance is best depicted after intravenous contrast material administration
 The second finding
 the detection of matrix mineralization in the lesion.

PAROSTEAL OSTEOSARCOMA
Parosteal osteosarcoma is a sarcoma that has its origin on the surface
of the bone.
Grows primarily into the surrounding soft tissues, but may also
infiltrate into the bone marrow.
Most commonly located on the posterior side of the distal femur.
Ossification in a parosteal osteosaroma is usually more mature in the
center than at the periphery. This is opposed to myositis ossificans
which also may present close to the cortical bone, but maturation
develops from the periphery to the center.
third and fourth decades of life and show a slight female predilection

Radiograph.
Homogeneous ossified mass adjacent to
the cortical bone of the distal femur.
Typical location and appearance of
parosteal osteosarcoma.
MRI
Sagittal T1-weighted MR image shows
partial very low signal intensity due to
the ossified matrix and the cortical bone
which is unimpaired.

Radiograph.
Small homogeneous mass adjacent to the
cortex of the diaphysis of the femur
MRI
Juxtacortical mass with enhancement of
the periphery.
Bone marrow and cortical bone are
otherwise normal.
Notice absence of reactive changes
around the lesion.
Differential diagnosis:
Organized reactive post-traumatic mass
like myositis ossificans.
Juxtacortical or Parosteal osteosarcoma,
because of the homogeneity of the
lesion.
Final diagnosis: parosteal osteosarcoma

The findings are:
A well-defined and homogeneous
sclerotic mass with a broad base to the
underlying diaphysis of the fibula.
A juxtacortical or parosteal osteosarcoma
should be considered, particularly when a
history of trauma is lacking.
Final diagnosis: parosteal osteosarcoma

PERIOSTAL OSTEOSARCOMA
The radiologic appearance of periosteal osteosarcomas is usually
characteristic and distinctive from that of parosteal lesions. e surface
of the thickened diaphyseal cortex is scalloped, with perpendicular
periosteal reaction extending into a broad-based so-tissue mass
Accounts for 25% of all juxta-cortical osteosarcomas

SECONDARY OSTEOSARCOMA
5–7% of all osteosarcomas are the result of malignant transformation
of a preexisting benign lesion.
The vast majority of these secondary osteosarcomas are associated
with Paget disease (67–90% of cases) or previous irradiation (6–22%)
Paget’s associated
 Radiographs reveal a destructive process which is most often lytic (50–65%), or less
commonly, mixed or blastic, and an associated so tissue mass. In contradistinction
to primary osteosarcoma, this is usually without associated periosteal reaction

Bone tumors part one

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Bone tumors part one