Bone tumors in the unusual locations

BONE TUMORS IN THE
UNUSUAL LOCATIONS
Ramin Sadeghi, MD

KEY POINTS
􀁴 In contrast to the axial skeleton, metastases, myeloma and lymphoma are rare in the
foot
􀁴 Ewing’s sarcoma and chondrosarcoma are the most common primary malignant bone
tumours in the immature and mature foot respectively with the majority in the calcaneus
and metatarsal bones
􀁴 Osteoid osteoma is the most common benign bone tumour, often presents with
atypical symptoms, frequently arises in the talar neck and may be radiographically occult
􀁴 Subungual exostosis is by far the most common tumor-like lesion and is distinct from
a true osteochondroma
􀁴 In the calcaneus, giant cell tumours and chondroblastoma frequently occur in the
apophysis posteriorly and adjacent to the posterior calcaneal facet (epiphyseal equivalent
sites) whereas simple cysts and intraosseous lipoma typically arise in the anterior
calcaneus in the region of the critical angle
􀁴 Lesions in the foot do not have to achieve a large size to become symptomatic and the
small size of many bones means that involvement of an entire bone is not uncommon

LOCATION
In general, most bone tumours, whether malignant or benign, tend to
occur in the hind-/midfoot rather than the forefoot.
When malignant tumours do occur in the forefoot, involvement of the
metatarsals is much more common than the phalanges.
On the other hand, benign tumours of the phalanges are not
uncommon with the majority due to chondroma
Some bone tumours have a predilection for a particular bone.
Osteoid osteoma and osteoblastoma commonly arise at the talar
neck, and simple bone cysts and intraosseous lipomas in the anterior
third of the calcaneus

LOCATION
The calcaneus has identifiable sites that correspond to the physeal
zones.
The calcaneal apophysis and the subarticular portions of the upper
and anterior calcaneus correspond to the epiphysis equivalent zone,
the adjacent bone corresponds to the metaphyseal zone, and the
central calcaneus to the diaphyseal zone.
 Chondroblastoma and giant cell tumours frequently occur in the apophysis
posteriorly and adjacent to the posterior calcaneal facet, both epiphyseal equivalent
sites. Of the malignant bony lesions,
 Metastases and Ewing’s sarcoma tend to occur centrally in the body and tuberosity
of the calcaneus, but osteosarcoma has no predilection for site

BENIGN TUMOURS AND TUMOUR-
LIKE LESIONS

OSTEOID OSTEOMA
The most common benign tumour of the foot with the majority found
in the superior aspect of the talar neck and subarticular portions of
the calcaneus.
A peak incidence in the second decade
lesions in the hind- and midfoot are intra-medullary or subperiosteal,
provoke little osteoblastic response
the characteristic ‘double density sign’ on bone scintigraphy,
commonly seen in cortical lesions is often absent in intra-articular
lesions due the generalized uptake of the associated synovitis

CHONDROBLASTOMA
Favours an epiphyseal or subarticular location, which accounts for the
high incidence in the subarticular regions of the talus and calcaneus
and calcaneal apophysis
3rd decade of life
Radiographically, lesions are typically translucent, with well-defined,
often sclerotic margins and mineralisation can be present in up to
54%
On MR imaging, lesions are typically inhomogeneous and
surrounding marrow oedema is common

CHONDROMA
is the most common benign bone tumour of the forefoot.
Chondromas most commonly present with a painless swelling or
pathological fracture in the third and fourth decades.
On T2-weighting, thin, low signal intensity, septae are noted between
the lobules of high signal intensity cartilage. Following intravenous
contrast, there is typically septal and peripheral enhancement.
Mineralised components show low signal intensity on all sequences
although rare, malignancy should be suspected where the lesion
measures >5 cm2 in size or arises in the mid- or hindfoot

GIANT CELL TUMOUR
predominates in the hindfoot, typically in the head/neck of the talus
and tuberosity and subarticular portions of the calcaneus.
Aneurysmal cyst components and haemorrhage are noted in up to
24% of giant cell tumours
MR images typically show an inhomogeneous appearance, with foci of
variable signal intensity and often fluid-fluid levels
 DDx: ABC
 Younger age less aggressive pattern, lacks solid enhancing components and no so tissue
extension

CHONDROMYXOID FIBROMA
has a predilection for the foot, most commonly the metatarsals,
calcaneus and phalanges
Radiographs typically show a slow-growing, well-defined, expansile,
osteolytic lesion often with sclerotic margins. Matrix calcification is
rare.
On MR imaging, lesions display inhomogeneous, intermediate to high
signal intensity on T2-weighting due to chondroid, myxoid and brous
components as well as intralesional haemorrhage. The margin of the
lesion usually displays low signal intensity on all sequences,
reflecting reactive bone.

ANEURYSMAL BONE CYST
Lesions predominate in the tarsus and in particular, the posterior
aspect of the calcaneus. In the thin tubular bones of the foot, lesions
often expand the whole bone.
Lesions are most common in the second decade and later
presentation should raise the possibility of an underlying lesion, most
commonly, a giant cell tumour

SIMPLE BONE CYST
have a predilection for the calcaneus in adults
Radiographs reveal a well-defined lytic lesion often with a sclerotic
rim in the critical angle of the anterior third of the calcaneus.
Pseudocysts can appear similar but are less well-defined, and internal
trabeculations are often present

INTRA-OSSEOUS LIPOMA
has a predisposition for the critical angle of the anterior calcaneus
It is characterised by a well-defined, radiolucent lesion, less that 4
cm in size with a thin sclerotic rim (61%). ere may be a central calcific
density representing dystrophic calcification
On MRI, appearances will vary with the extent of necrosis and cyst
formation but all contain at least some MR detectable fat. Calcific foci
and cyst formation are common.

CHONDROSARCOMA
second most common primary bony malignancy of the foot,
e majority arise in the calcaneus and metatarsals and presentation is
most commonly in the sixth and seventh decades. Chondrosarcoma
of the hindfoot is more likely to metastasise than phalangeal
chondrosarcoma, which only rarely metastasises and behaves as a
locally aggressive lesion
The typical punctate calcifications are best shown on CT. On MR
imaging, the signal characteristics may be similar to enchondroma,
but chondrosarcoma should be strongly suspected where there is
cortical destruction, periosteal reaction and so-tissue infiltration

OSTEOSARCOMA
is the third most common primary bony malignancy of the foot
As many as 75% are located in the tarsus and 75% of those arise in
the calcaneus. In contrast to osteosarcoma of the long bones,
patients present most commonly in the fourth decade
Amorphous or cloud-like mineralisation is common and a lamellated
or spiculated periosteal reaction is often present

EWING’S SARCOMA
Ewing’s sarcoma is the most common primary bone sarcoma of the foot
Lesions are most commonly found in the calcaneus and metatarsal bones
and usually present with a painful swelling in the second decade.
Most lesions in the tubular bones show “classic” appearances with an
aggressive permeative pattern of bone destruction in a metadiaphyseal
location and a so-tissue mass
lack of mineralised matrix helps dierentiate Ewing’s sarcoma from
osteosarcoma. On MR imaging, lesions are usually hypointense or isointense
compared with muscle on T1-weighting and hyperintense and
inhomogeneous on T2-weighting. Ewing’s sarcoma often mimics
osteomyelitis, both radiographically and clinically.

METASTASES
are rare
Primary tumours are mostly due to adenocarcinoma from the colon
(17%), kidneys (17%), lung (15%), bladder (10%), and breast (10%).
In the foot, the tarsal bones are more commonly involved than the
forefoot, and the majority of these occur in the calcaneus.

KEY POINTS
􀁴 Benign neoplasms and tumour-like conditions represent 85% of lesions in the
patella.
􀁴 Chondroblastoma, giant cell tumours, and aneurysmal bone cyst are the three
commonest lesions.
􀁴 In patients older than 40 years of age, primary and secondary malignancies,
intra-osseous ganglion, and gouty tophi should also be included in the
differential diagnosis.
􀁴 The possibility of haematogenous osteomyelitis should be considered in
children and teenagers between 5 and 15 years of age.
􀁴 The age, medical history and clinical context are of great help as the imaging
features frequently are non-specific.
􀁴 Because of the sesamoid origin and size of the patella, typical features of
bone tumours, as might be seen in the long bones, such as periosteal new bone
formation, may be missing.

BENIGN TUMORS
Most common
 is particularly applies to patients presenting below 40 years of age. Giant cell
tumour and chondroblastoma account equally for more than 50% of benign lesions

CHONDROBLASTOMA
It appears radiographically as a round or lobulated focus of bone
destruction, surrounded by a well-dened sclerotic rim
The contour of the patella is usually preserved, unless the
chondroblastoma is associated with a secondary aneurysmal bone
cyst
Matrix mineralization is frequently absent. CT can depict matrix
mineralization and soft tissue involvement
MR imaging demonstrates low signal intensity on T1-weighted
images and variable signal intensity on T2-weighted images with foci
of hypointense signal corresponding to the mineralization. Fluid-
fluids levels can be observed

GIANT CELL TUMOUR
typically affecting the subarticular portion of long bones during the 3rd
decade of life
Radiographs and CT show a geographical pattern of bone destruction, with
well- to ill-defined margins, involving more than 75% of the patella.
Compared to chondroblastomas, GCT tends to be larger in size and
therefore involves a greater proportion of the patella.
Cortex thinning, bone expansion and “bubbly” appearance of the patella
related to septa are typical
MR imaging demonstrates low to intermediate signal-intensity on T1-
weighted images and intermediate to high signal intensity on T2- weighted
images. Low signal foci related to haemosiderin deposition within the
tumour may be observed, and fluid-fluid levels would again suggest
secondary ABC formation.

MALIGNANT TUMOURS
The most frequent aetiologies reported are metastasis, osteosarcoma,
haemangioendothelioma and lymphoma
Radiographically, most of them cannot be reliably distinguished from
benign neoplasms.
Clinical context, medical history and age of patient may raise the
question of possible malignancy.

METASTASES
Metastases from lung cancer appear to be the most frequently
reported

PRIMARY MALIGNANT TUMOURS
Lymphoma, haemangioendothelioma and osteosarcoma are the most
frequent primary malignant tumours in the patella
Interestingly, no periosteal reaction should be expected as the
patella, being a sesamoid bone, does not have a conventional
periosteal layer

TUMOUR-LIKE LESIONS
Aneurysmal bone cyst and osteomyelitis are the commonest non-
neoplastic conditions in children and young adults, whereas the
diagnosis of intraosseous gout and brown tumour of
hyperparathyroidism should be favoured in adults older than 40 years
of age.

It is the third commonest lesion arising in the patella, after
chondroblastoma and GCT,
Fluid-fluids levels on CT or MR imaging strongly suggest the
diagnosis of ABC, but should be considered with caution and should
not exclude a primary bone lesion with secondary ABC or even
malignancy.

OSTEOMYELITIS
Acute haematogenous osteomyelitis of the patella typically occurs
between 5 and 15 years of age.
Staphylococcus aureus is themost common micro-organism causing
the infection
Tuberculosis should be mentioned as a possible cause, especially in
immunocompromised patients, but tends to be multifocal rather than
isolated in the patella.
appear as a non-specic small radiolucency. It is best demonstrated
on CT or MR imaging.

INTRAOSSEOUS GOUT
Intraosseous tophi are rare ndings, appearing as well-delineated
lucent lesions. The foot and ankle are the most commonly involved
joints, with the knee in third position.
The main characteristic of intraosseous tophi of the patella is the
associated soft tissue mass, which presents usually with
calcifications.
Involvement of adjacent so tissue is best demonstrated on CT or MR
imaging

BROWN TUMOURS
They appear as well-defined, largely lytic lesions. MR imaging
demonstrates low signal intensity of the lesion on both T1- and T2-
weighted images, with possible hyperintense foci on T2-weighted
images.
The low signal intensity is likely due to repeated intralesional
haemorrhage

KEY POINTS
􀁴 Bone tumours of the hand and wrist are uncommon.
􀁴 The majority of these tumours are benign.
􀁴 Enchondroma is the commonest benign tumour.
􀁴 Chondrosarcoma is the commonest malignant primary tumour.
􀁴 Malignant tumours of the hand frequently have a better prognosis
than tumours at other skeletal sites.

The majority of bone tumours that affect the hand are benign
Radiographs are sufficient to allow accurate diagnosis in the majority
of bone tumours of the hand and wrist.
Computed tomography allows characterisation of tumour matrix and
presence of bone destruction.
MRI provides information regarding the extent of marrow involvement
and so tissue invasion.

ENCHONDROMA
40% of all enchondromas of the body are located in the phalanges
and 10% in the metacarpals.
Typically, patients present with a pathological fracture following
minor trauma.
Radiographs show the tumour to be typically located in the meta-
diaphyseal region of the tubular bones of the hand. It is classically a
well-defined cystic, radiolucent intramedullary lesion containing thin
internal trabeculations
Associated chondroid calcifications are noted less often in
enchondromas of the hand

MR imaging: multiple lobules of high signal intensity on T2W and
STIR sequences, Low signal septae are often seen separating the
lobules. Low signal foci corresponding to chondroid matrix may also
be apparent

GIANT CELL TUMOURS OF BONE
The distal radius is the third most common site of origin of giant cell
tumour of bone (GCTOB), accounting for approximately 10% of cases.

The metacarpals and phalanges effectively represent the equivalent of
a long bone in the hand.
The tumour occurs in a more central location in the bones of the
hand probably due to the limited volume of bone.
A narrow zone of transition is seen at the metaphyseal margin of the
lesion and there is typically no matrix mineralization.
Internal trabeculation is common but the pattern may vary from fine
striations to coarse trabeculation.
Periosteal reaction is unusual unless there is a complicating fracture

Technetium 99m bone scintigraphy may demonstrate a classic
“doughnut” configuration with avid uptake at the periphery of the
tumour and a relatively photopenic centre.
MRI denes the intra- and extra-osseous extent of the tumour. Low
signal intensity on all sequences can be seen which is indicative of
chronic haemosiderin deposition in GCTOB
Fluid-fluid levels may be demonstrated within the tumour mass
indicating the presence of secondary aneurysmal bone cyst (ABC)
formation.

ANEURYSMAL BONE CYSTS
Involvement is most commonly seen in the metacarpals (52%) followed by
the phalanges (36%) and carpal bones (4%)
Radiographs of the hand demonstrate a central, expansile, lytic lesion which
causes cortical thinning
A sclerotic margin may be present. Matrix trabeculations are sometimes
observed and may be mixed or lytic.
Pathological cortical fractures are associated with a periosteal reaction.
When the lesion presents in the distal phalanx, significant bone destruction
may occur.
MR and CT imaging, as in other skeletal locations, may demonstrate fluid-
fluid levels which are suggestive but not diagnostic of ABC.

OSTEOID OSTEOMA
Painless osteoid osteoma appears to occur in the digits more
frequently than in any other skeletal location
Regarding imaging ndings, the typical radiographic appearance is
that of a small, radiolucent lesion or nidus surrounded by an area of
bone sclerosis
Initial radiographs in almost all of the patients were normal, with
bony abnormality becoming visible from 6 to up to 25 months.
In cases where radiographs and bone scintigraphy are equivocal, CT
should be obtained. is characteristically shows a lytic lesion with a
central granular opacity surrounded by a sclerotic margin.

OSTEOCHONDROMA
Only 4% of solitary osteochondromas involve the hands
The overall incidence of hand lesions is 79% in patients with HME
 The ulnar metacarpals and proximal phalanges are most commonly affected, with
the thumb and distal phalanges less commonly involved.
A chondrosarcoma of the hand arising in a patient with HME has twice
been reported in the literature
are typically sessile lesions which show continuity with the underlying
medullary cavity of the bone of origin
MR imaging provides precise information about thickness of the
cartilage cap which has high signal intensity on T2 spin echo
sequences and is important when assessing potential malignant
transformation

BIZZARE PAROSTEAL
OSTEOCHONDROMATOUS
PROLIFERATION (BPOP).
A well marginated, calcified or osseous mass is seen to arise from
cortex on radiographs. Its lack of continuity with the medulla, which
can be clearly demonstrated on CT, differentiates this lesion from an
osteochondroma. It most commonly arises in the proximal and
middle phalanges and typically presents in the third and fourth
decades

INTRAOSSEOUS EPIDERMAL CYSTS
Peak incidence is within the 25–50 age group with a male to female
ratio of 3:1
The most common site is the terminal phalanx of the left middle
finger
On radiographs, they usually appear as a well-defined, unilocular,
osteolytic lesion with a sclerotic margin and may exhibit spotty
calcifications
Enchondroma is the major differential diagnosis but, unlike
intraosseous epidermal cysts, it is rarely symptomatic in the absence
of a fracture.

GLOMUS TUMOURS
are benign hamartomas. They arise from the normal glomus
apparatus within sub-cutaneous tissue. The tumours mainly occur in
women and are most commonly located in the distal phalanx

CHONDROSARCOMA
Chondrosarcoma is the most common primary malignant tumour of
the hand
Chondrosarcoma of the hand tends to affect an older age group than
at other sites with an average age of 61.
They are more common in the proximal phalanx than the metacarpals
“secondary” chondrosarcomas account for 27% of chondrosarcomas
reported in the hand

the tumours tend to originate near the site of the epiphyseal growth
plate of the bone: proximally in the phalanx and distally in the
metacarpals
Typical features on radiographs include cortical destruction, a wide
zone of transition, matrix calcification, thickening and irregularity of
any cartilaginous cap, pathological fracture and so tissue extension
Soft tissue involvement was present in 77% of cases

EWING’S SARCOMA
The metacarpals are more commonly affected
has never been described arising within a carpal bone.
the characteristic permeative, lytic lesion with aggressive periosteal
reaction and cortical destruction is seen in the majority of cases.
The presence of bony reaction and associated so tissue mass often
makes differentiation from osteomyelitis difficult. A juxtacortical so
tissue mass is present in 89% of cases and can be detected by MR
imaging

OSTEOSARCOMA
Osteosarcoma of the hand typically occurs in an older population
than other skeletal sites with an average age of 45 years and the
prognosis is generally better
The tumour arises in the metacarpals and phalanges but has not been
reported in the carpal bones.
 There appears to be a greater propensity to arise from the surface of the bone
occurring in 30% of hand
matrix mineralisation, bone destruction and florid periosteal reaction.
The tumour is generally intramedullary with extension into the so
tissues. Surface osteosarcomas however often appear as a densely
calcified mass adjacent to a metacarpal or phalanx

METASTASIS
Any bone in the hand and wrist can be involved, though the most
commonly reported site is the terminal phalanx
Of skeletal wrist and hand metastases, 40–50% are from primary
bronchial carcinoma
Regarding imaging findings, radiographically metastases of the hand
appear most frequently as non-specific lytic, aggressive lesions which
may be misdiagnosed as infection or an inflammatory arthritis
particularly if there is no history of a primary tumour
Periosteal reaction is uncommon
A so tissue component is frequent but actual joint involvement is rare

KEY NOTES
􀁴 Metastases and myeloma are common in the bony pelvis, whereas other bone
tumours and tumour-like lesions are relatively uncommon.
􀁴 Primary malignant bone tumours of the pelvis are more common than benign
tumours with chondrosarcoma, the most common primary malignant bone
tumour in the mature pelvis (excluding myeloma), and Ewing’s sarcoma, the
most common in the immature pelvis.
􀁴 Osteochondroma is the most common benign tumour of the pelvis and
eosinophilic granuloma the most common tumour-like lesion.
􀁴 The majority of tumours and tumour-like lesions arise in the ilium.
􀁴 Due to anatomical factors, delay in the diagnosis of pelvic bone tumours is
not uncommon and lesions can grow to a relatively large size before detection.
􀁴 Although MR imaging is the cross-sectional imaging method of choice for
assessing pelvic tumours, CT is often a useful complementary technique in
identifying matrix and periosteal mineralisation and cortical destruction.

the most common malignant bone tumours around the bony pelvis
are metastases and myeloma,

In one study of pelvic bone sarcomas, the diagnosis was initially
missed in 44% of patients

LOCATION
the ilium is the most common site for malignant and benign bone
tumours
Cartilaginous lesions are more frequently found in the region of the
triradiate cartilage, but chondroblastoma and osteochondroma can
also be found in the iliac crest at the site of the apophysis
Giant cell tumours are typically subarticular or related to an old
apophysis

RADIOGRAPHIC FEATURES
Lesions in the pubis or ischium are more easily detected
lesions arising in thick cancellous bone, such as the ilium, may be occult
until there is enough destruction of the trabecular bone or evidence of
cortical involvement.
Some aggressive tumours, including round cell tumours, typically show a
permeative pattern of bone destruction with little or no apparent cortical
destruction
Mineralised cartilage is variously described as flocculent, stippled, annular,
comma shaped or popcorn calcification
Periosteal reactions may occur with benign and malignant pelvic tumours
and are more likely to be detected in the pubis or ischium rather than the
ilium.

Most lesions display non-specific low to intermediate signal intensity
(similar to that of muscle) on T1-weighting and high signal intensity
on T2-weighting.
However, some lesions or parts of lesions may have more
characteristic findings that may reduce the dierential diagnosis.
Cystic lesions, such as simple bone cysts, display homogeneous low
signal intensity on T1-weighting, very high signal intensity on T2-
weighting and show no or minimal rim enhancement.
Fluid-fluid levels occur in various benign and malignant bony lesions
and represent the sedimentation effect of blood.
 When seen in an expansile bone lesion in an adolescent, fluid-fluid levels are highly
suggestive of an aneurysmal bone cyst

BENIGN MINERALISING BONE
LESIONS
Chondroblastoma
 Most of them arise at the site of an old apophysis, usually around the triradiate
cartilage of the acetabulum or the iliac crest
 A surrounding inflammatory response is common, and fluid-fluid levels
may be present
 The presence of matrix mineralization helps differentiate it from
eosinophilic granuloma, Brodie’s abscess and giant cell tumour.
Chondromas (enchondromas)
 On MR imaging, T2-weighted images show multiple lobules of high signal intensity
cartilage separated by thin, low-signal septae that enhance following intravenous
contrast.
 Mineralised components show low signal intensity on all sequences.

BENIGN MINERALISING BONE
LESIONS
Osteoid osteoma
CT is diagnostic
On MR imaging, appearances can be confusing, as there is typically
extensive marrow oedema and surrounding inflammatory changes
that may obscure the nidus or suggest another process such as
infection, trauma or tumour.

BENIGN LYTIC AND CYSTIC
LESIONS
Giant cell tumour
 it is the second most common benign pelvic bone tumour
 Radiographically, lesions are typically osteolytic, expansile and subarticular in
location, although they may also arise at the site of an old apophysis
 On MR imaging, lesions are inhomogeneous with variable signal intensity and often
fluid-fluid levels
 CT is sensitive in demonstrating faint mineralisation in the periosteal shell and
excludes intra-lesional mineralisation that might otherwise suggest an osteoblastic
or cartilaginous tumour
 In the older patient, the differential diagnosis includes expansile
metastasis, myeloma and primary bone sarcoma including
chondrosarcoma.

LESIONS
Chondromyxoid fibroma
 Unlike most cartilaginous tumours, matrix calcication is uncommon
 radiologically indistinguishable from giant cell tumour, fibrous dysplasia,
chondroblastoma or chondroma
The simple (unicameral) bone cyst
 Lesions predominate in the iliac wing and, to a lesser extent, posterior
ilium adjacent to the sacroiliac
 Radiographs reveal a well-defined lytic lesion often with a sclerotic rim.

A well-defined lytic lesion with sclerotic
margin in the right iliac wing of an adult.
Benign characteristics. Diagnosis is SBC.
SBC can be encountered as an
asymptomatic coincidental finding in the
pelvis.

LESIONS
Aneurysmal bone cyst
 typically arising around the triradiate cartilage.
 Most of the cysts are primary lesions, although aneurysmal bone cyst-like features
can be found with other precursor lesions, including giant cell tumour,
osteoblastoma, chondroblastoma and the rare telangiectatic osteosarcoma

LESIONS
Fibrous dysplasia
 commonly affects the bony pelvis
 Radiographs show a well-defined, intramedullary, expansile lesion often
with endosteal scalloping and sclerotic margin of variable thickness

LESIONS
Eosinophilic granuloma
 radiographs and MR imaging typically demonstrate an aggressive pattern of bone
destruction with ill-defined margins and lamellated periosteal reaction simulating
Ewing’s sarcoma, lymphoma or infection
 however, in the later healing phase, they have well-defined sclerotic margins
simulating a benign bone tumour, including chondroblastoma, enchondroma, brous
dysplasia or simple bone cyst

BENIGN SURFACE LESIONS
Osteochondroma
 the most common benign bone tumour of the pelvis accounting
 Most pelvic lesions arise in the iliac bone
 Radiographically, lesions appear as a sessile or pedunculated exophytic outgrowth
from the bone surface that shows continuity with the marrow cavity and cortex.
 A painful lesion or continued growth after maturity should raise the possibility of
sarcomatous degeneration

MALIGNANT MINERALISING
SARCOMAS
Chondrosarcoma
 the most common primary bone sarcoma around the pelvis
 71% of these arise in the ilium and around the acetabulum.
 the vast majority of cartilagenous tumours in the pelvis are malignant, and
therefore all cartilagenous tumours of the pelvis should be viewed with suspicion
 Cortical scalloping greater than two-thirds of the cortical thickness, lesion size
greater than 5 cm, non-mechanical pain and patient age over 30 years are strongly
supportive of chondrosarcoma
 CT is the most sensitive technique for detecting mineralisation

MALIGNANT MINERALISING
SARCOMAS
Osteosarcoma
it is the second most common primary bony malignancy of the pelvis
The radiological appearances are variable, but most lesions display a
mixed lytic/sclerotic appearance with a moth-eaten or permeative
pattern of bone destruction and so tissue extension. Matrix
chondroid or osteoid mineralisation is usually present and helps to
differentiate from other sarcomas including Ewing’s sarcoma.

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.

MALIGNANT NON-MINERALISING
SARCOMAS
Ewing’s sarcoma
 Lesions are most commonly found in the ilium and may spread across the sacroiliac
joint, but involvement of the hip joint is unusual. Radiographs show an aggressive
lytic lesion with a moth-eaten or permeative pattern of bone destruction and
lamellated periosteal reaction that may be difficult to detect in the pelvis
 Acute osteomyelitis and eosinophilic granuloma may mimic Ewing’s sarcoma as all
three conditions may present with a fever and leukocytosis

NON-SARCOMATOUS BONE
MALIGNANCIES
Multiple myeloma
is the most common primary malignant bone neoplasm around the
pelvis with a peak incidence between the sixth and seventh decades
The ilium is a common site for solitary plasmacytoma

MALIGNANCIES
Lymphoma
 the majority of lesions display an aggressive, predominantly lytic appearance with a
moth-eaten or permeative pattern of bone destruction, periosteal reaction and
occasionally sequestra, but in the pelvis these features may be difficult to detect
radiographically
 On MR imaging, there is often a large parosseous so tissue component
 In the younger patient, the main differential diagnoses are Ewing’s sarcoma,
osteosarcoma, Langerhans’ histiocytosis and osteomyelitis, and in the older patient,
metastases and myeloma.

MALIGNANCIES
Metastases
 the most common tumours around the bony pelvis.
 Radiographically, the majority of these lesions are lytic with a geographic or moth-
eaten pattern of bone destruction and absent periosteal reaction.
 Occasionally, metastases have an expansile appearance indicating a slower rate of
growth and often a renal or thyroid origin
 The differential diagnosis of osteolytic metastases includes myeloma and
lymphoma, and if solitary, primary bone sarcoma including chondrosarcoma,
malignant fibrous histiocystosis and fibrosarcoma
 The differential diagnosis of sclerotic metastases includes bone islands, bone
infarcts, Paget’s disease, osteitis condensan ilii, and less commonly, lymphoma,
Ollier’s disease and sclerosing dysplasias

TUMOURS OF THE RIBS AND
CLAVICLE

KEY POINTS
􀁴Primary bone tumours of the ribs, clavicle and sternum are uncommon.
􀁴 Infection and stress-related injuries often present as clavicle
pseudotumours.
􀁴 The majority of tumours of the clavicle are malignant and the most
common are plasmacytoma, osteosarcoma and Ewing’s sarcoma.
􀁴 Aneurysmal bone cysts and eosinophilic granuloma are the most common
benign lesions of the clavicle.
􀁴 Myeloma, chondrosarcomas and Ewing’s sarcoma are the most common
primary bone tumours that involve the ribs.
􀁴 Enchondromas and fibrous dysplasia are the most common benign rib
lesions.
􀁴 The majority of tumours of the sternum are malignant, and the most
common are chondrosarcoma, myeloma and osteosarcoma.

NON-AGGRESSIVE SCLEROTIC
LESIONS OF THE CLAVICLE
Degenerative change of the sternoclavicular joint sometimes
manifests as a palpable abnormality
 Significant sclerosis and irregularity of the medial clavicle may occur
 This is a pseudotumor
Osteitis condensans
 in females older than 30 years.
 It is characterized by pain with the absence of local or systemic inflammatory
symptoms. Sclerosis and enlargement of the medial clavicle is present on
radiographs.
 It tends to affect the inferior aspect of the medial clavicle in most cases.
 Absence of sternoclavicular joint arthritis and lack of associated so tissue mass on
cross-sectional imaging are important findings

NON-AGGRESSIVE SCLEROTIC
LESIONS OF THE CLAVICLE
SAPHO
 SAPHO is an acronym referring to a syndrome characterized by synovitis, acne,
pustulosis, hyperostosis and osteitis
 In adults, the sternocostoclavicular region is the most frequent site of involvement.
Radiographic hallmarks include sclerosis and expansion of the involved bone.
Lymphoma, Ewing’s sarcoma, eosinophilic granuloma and
osteosarcoma are considerations when a young patient presents with
sclerosis of the clavicle.
Metastatic disease should be a strong consideration in the older
patient with a sclerotic lesion in the clavicle.

NON-AGGRESSIVE LUCENT LESIONS
OF THE CLAVICLE
Metastases and myeloma are the most common cause of lucent
clavicular lesions in patients over 40 years.
In younger patients, eosinophilic granuloma and aneurysmal bone
cysts have a predilection for the clavicle.
 ABC
 the majority occur in patients under 20 years. In one series of six cases, all cysts occurred in the distal
clavicle
 EG
 a well-defined lucent lesion is the most common manifestation. Prominent periosteal
reaction and aggressive appearance may be seen, particularly when cortical destruction is
present.
 A predilection for the distal clavicle has been noted
In general, cartilage-forming tumours are rarely found in the clavicle.

AGGRESSIVE-APPEARING
CLAVICULAR LESIONS
The three most common primary tumours of the clavicle are
myeloma, osteosarcoma and Ewing’s sarcoma

RIBS
Metastases and myeloma are the first and second most common
tumours of the ribs, respectively, and should be considered in the
differential in most rib masses.
Location in clavicle
 Cartilageous tumors
 In the costochondral junction or posteriorly
 Myeloma, metastatic disease and fibrous dysplasia
 In the shaft

SCLEROTIC, INTRAMEDULLARY
LESIONS OF THE RIB
The dierential diagnosis for a sclerotic, intramedullary lesion of the
ribs includes
 osteoblastic metastases, osteoblastoma, osteosarcoma, osteoid osteoma, Paget’s
disease, calcifying enchondroma and ossifying fibroxanthoma
osteoblastic metastases are the most common
Enostoses are common in the ribs (second only to the pelvis) with a
0.4% prevalence in the population.
 They characteristically demonstrate homogenous density similar to cortical bone
with feathered, radiating bony margins on radiographs and computed tomography
Less than 1% of osteoid osteomas involve the ribs.
Approximately 2% of Paget’s disease involves the ribs

RIB LESIONS WITH AGGRESSIVE
APPEARANCE IN YOUNG PATIENT
Aggressive-appearing rib lesions in patients under 30 years are most
commonly secondary to infection, lymphoma, Ewing’s sarcoma,
eosinophilic granuloma and osteosarcoma.

RIB LESIONS WITH AN AGGRESSIVE
APPEARANCE IN THE OLDER PATIENT
Metastases and myeloma are by far the most common cause of
lesions in the older patient
Multiple myeloma generally occurs in patients older than 40 years.
Rib involvement is common, seen in 50% of patients.
 occur anywhere but the mid-portion of the rib is characteristic

RIB LESIONS WITH AN AGGRESSIVE
chondrosarcomas occur in the ribs making this the most common
primary malignancy, other than myeloma, to affect this location.
 occur in the anterior aspect or posterior aspect of the rib, and are usually
associated with a so tissue mass
Other chondroid forming tumours, such as chondroma,
chondromyxoid fibroma and chondroblastoma of the ribs, may
occur but are rare

RIB LESIONS WITH NON-AGGRESSIVE
APPEARANCE IN A YOUNG PATIENT
Fibrous dysplasia represents the most common benign neoplasm of
the ribs
 with a predilection for the second rib
 Radiologically, the lesions are centrally located within the rib and may be mildly
expansile.
 Soft tissue changes are uncommon in the absence of pathological fracture or
malignant degeneration.
 In general, they occur posterior and lateral in the ribs,
 A ground-glass matrix is frequently present, although the lesions are lucent or
sclerotic in other cases

APPEARANCE IN A YOUNG PATIENT
Enchondromas are the second most common rib tumour,
Prominent expansion can be more common in the ribs and is termed
enchondroma protuberans.
CT can be helpful to identify calcified chondroid matrix.
On MR imaging, these lesions have high signal on T2 and low signal
on T2 due to the high water content of cartilage is present.

Again, the most common non-aggressive lesions in older patients are
metastases and myeloma.
Fibrous dysplasia and enchondromas less commonly present in older
patients but remain considerations.
Brown tumours of hyperparathyroidism may also occur and are
generally multiple. Most other benign lesions tend to be unusual in
older patients.

STERNAL TUMOURS
The most common sternal tumours are metastases – most commonly
from the malignant tumours of breast, lung, kidney and thyroid
Chondrosarcoma is the most common primary, followed by myeloma,
lymphoma and osteosarcoma.
Computed tomography is valuable in characterizing tumour matrix
and aiding in the differential. Chondrosarcomas are usually found at
the junction of the ribs.
Solitary plasmacytomas are relatively common in the sternum
comprising 5−25% of primary sternal tumours.
Osteosarcomas of the sternum usually occur secondary to radiation

KEY POINTS
􀁴Bone tumors are less common within the scapula.
􀁴 Characteristic imaging features may be present or absent.
􀁴 Being a .at bone with complex anatomy, diagnosis and staging of
tumors may be more difcult compared with long bones.
􀁴 A combination of imaging modalities is best to characterize, stage,
and preoperatively image these lesions.

A variety of malignant and benign tumors may occur within the
scapula.
Cartilaginous tumors are the most frequent
Regarding benign and malignant tumors in the pediatric age group,
osteochondroma and Ewing’s sarcoma, respectively, and in the adult
age group, osteochondroma, chondrosarcoma, multiple myeloma,
and metastases respectively, should be considered.
 Osteochondromas are mostly located within the body of scapula, whereas
chondrosarcomas are mostly located at the lateral scapula margin over the inferior
angle and within the acromion and coracoid process

OSTEOCHONDROMA AND HEREDITARY
MULTIPLE EXOSTOSES
a well-known entity

MALIGNANT BONE TUMORS OF
SCAPULA
After the pelvis (25% all cases), the scapula (5%) is the second most
frequently involved .at bone with chondrosarcoma
Benign enchondromas are extremely rare in this site and therefore
any cartilaginous lesion in this region should be treated as neoplastic
in nature and not reactive
Peak incidence is during the sixth and seventh decades
Chondrosarcomas are located mainly at the medial scapula margin,
and over the inferior angle, corresponding to the sites of highest
growth potential within the scapula during enchondral ossication, and
in the acromion and coracoid process, the secondary ossication
centers with physe

OSTEOSARCOMA
Patients present in the second or third decades or later, after the
sixth decade

EWING’S AND PNET SARCOMA
Involving the scapula Ewing’s and primitive neuroectodermal tumor
(PNET) sarcomas occur in the young age group, often destroying a
large component of the body and glenoid regions, and are associated
with large so tissue masses

KEY NOTES
􀁴 In children and adults, metastases are both the most frequent tumor of
bone and the most frequent tumor of the axial skeleton
􀁴 The age of the patient, favored location of specific tumors in the axial
skeleton, and its relative frequency is essential to evaluating a vertebral
tumor
􀁴 On the basis of location within the vertebrae, lesions with a predilection
for the posterior elements include aneurysmal bone cyst, osteoid osteoma,
osteoblastoma, osteochondroma, Ewing sarcoma, osteosarcoma,
chondrosarcoma
􀁴 On the basis of location within the vertebrae, lesions with a predilection
for the vertebral body include metastases, Langerhans cell histiocytosis of
the spine, giant cell tumor, hemangioma, plasmacytoma, myeloma and
lymphoma
􀁴 Lesions with a predilection for the sacrum include Paget’s disease,
chordoma, giant cell tumor and benign notochordal cell tumors

INTRODUCTION
Primary tumors of the vertebral column are far less common than
metastatic lesions.
Often, one can arrive at an accurate pre-histologic diagnosis, with
patient age, history and an understanding of imaging characteristics
of a lesion with a predilection for the vertebrae and sacrum.

METASTASES
The axial skeleton is the most common site for osseous metastases.
The thoracic spine is the most commonly affected.
In the pediatric population, neuroblastoma and leukemia are the most
common primary malignancies to metastasize.
In the adult population, breast, prostate, and lung carcinomas are the
most common primary malignancies to metastasize.
The vertebral body, the subchondral regions, anterior margins and
pedicles are the earliest sites of involvement

PEDIATRIC AGE GROUP
in the 0–5 age range,
 Benign
 Langerhans cell histiocytosis
 Malignant
 Ewing Sarcoma, leukemia and metastatic neuroblastoma and Wilms tumor
In the 5–10 age range,
 benign
 aneurysmal bone cyst, Langerhans cell histiocytosis, non ossifying fibroma, osteoblastoma, and osteoid osteoma.
 Malignant
 Ewing sarcoma and osteosarcoma
In the 10–20 age range,
 Benign
 Aneurysmal bone cyst, osteochondroma, and osteoid osteoma
 Malignant
 chondrosarcoma joins the list of malignant considerations

BENIGN LESIONS IN THE
PEDIATRIC POPULATION

LANGERHANS CELL
HISTIOCYTOSIS OF THE SPINE
Peak incidence 5-10 years
LCH typically involves the vertebral body and is an aggressive-
appearing osteolytic lesion leading to vertebral collapse, with
complete collapse giving the characteristic appearance of vertebra
plana
In older children, the degree of destruction is less severe, and
vertebra plana is less common.
Since LCH is multifocal in half of patients, a skeletal survey or bone
scan can be done to identify other lesions.

up to 20% are located in the spine.
Approximately 80% present in patients in the first two decades of life
Either the posterior elements alone, or the vertebral body in addition to the
posterior elements, are involved.
Aneurysmal bone cysts do not usually involve the vertebral body without
extending into posterior elements.
The lesion is usually purely lytic with expansion leading to a thin shell of bone
seen at the periphery, which is a defining feature of an aneurysmal bone cyst
Lesions can span two and even three adjacent vertebrae which is a distinguishing
feature of an aneurysmal bone cyst
DDx
 in the sacrum may be difficult to distinguish from giant cell tumor in young adults.
 Aneurysmal bone cysts without an identifiable rim may be difficult if not impossible to distinguish
from osteoblastoma.

OSTEOBLASTOMA AND OSTEOID
OSTEOMA
Lesions less than 1.5–2 cm in diameter are called osteoid osteomas,
whereas those larger than 2 cm are called osteoblastomas.
Approximately 40% of all osteoblastomas are located in the spine
Most osteoblastomas are localized to the posterior element, with
vertebral body involvement following posterior element involvement
These lesions may demonstrate expansion, an osteoid matrix, and
measure greater than 2 cm in diameters. More aggressive lesions
demonstrate extension into the adjacent so tissue and cortical
destruction

OSTEOCHONDROMA
they are the most common benign tumors in the pediatric population.
Spinal involvement is seen in 3% of cases, with the cervical spine the
most common site in the axial skeleton
Lesions are usually asymptomatic unless there is impingement on the
spinal canal or neuroforamina. Radiographically, the hallmark of an
osteochondroma is the continuity of the cortex between normal bone
and the lesion

MALIGNANT LESIONS IN THE
PEDIATRIC POPULATION

EWING SARCOMA
Ewing sarcoma is the most common primary malignant bone lesion in
the pediatric population up to age ten
the sacrum is the most frequent site of involvement followed by the
thoracic and lumbar spine
Typical radiographic appearance is that of a permeative destruction
with periosteal reaction and adjacent so tissue mass and spinal canal
invasion. In the majority of lesions in the nonsacral spine, there was
involvement of the posterior elements with extension into the
vertebral body.
The ala was the most frequently affected site in the sacrum.

OSTEOSARCOMA
the mean age of incidence of vertebral osteosarcoma in the fourth
decade
The lesions most often involve the posterior elements with extension
through the pedicles to the vertebral body
Sacral tumors usually involve the body and sacral ala

CHONDROSARCOMA
there is a predilection for the thoracic spine. The sacrum is seldom
involved
As many as 40% of lesions arise from the posterior elements of the
spine. More commonly, however, both vertebral body and posterior
elements are involved

GIANT CELL TUMOR
Giant cell tumors are usually seen in patients in the second to fourth
decade of life.
Giant cell tumors are the most frequently encountered sacral tumor
after chordoma
In the sacrum, the lesion is well defined, lytic, with expansion and no
surrounding sclerosis and sometimes extension to SI joint
Vertebral lesions are rare, but when present the lesion usually affects
the vertebral body
Most lesions have an extraosseous component

HEMANGIOMA
Hemangiomas are usually found after the fourth decade of life. there
is a predilection for the thoracolumbar spine; usually only the
vertebral body is involved.
Vertebral hemangiomas are the most common benign spinal
neoplasm.
Large hemangiomas are seen on radiographs as coarse striated or
honeycomb appearance of the involved vertebral body. On CT,
vertebral hemangiomas produce a polka-dot appearance.
Hemangiomas can have a wide range of appearances on MR
depending on the ratio of vascular vs fatty stroma

CHONDROBLASTOMA AND OTHER
BENIGN CARTILAGINOUS TUMORS
Chondroblastoma
 Expansive and most demonstrate aggressive features with so tissue mass and bone
destruction. Calcification was seen

CHORDOMA AND BENIGN
NOTOCHORDAL CELL TUMORS
chordoma is the most common primary malignant sacral neoplasm.
This malignancy is found in all ages but peaks in the fothh to sixth
decade.
Radiographically, chordomas present as an expansive lesion with a
central area of bone destruction with a so tissue mass that may
contain calcification
About half of chordomas occur in the sacrum, another 35% occurs in
the suboccipital region
DDx
 chondrosarcoma and giant cell tumor.
 However, chondrosarcoma usually affects the upper two sacral segments whereas chordomas usually
originate from the lower sacral segments or the coccyx.

Bone tumors in the unusual locations

Bone tumors in the unusual locations

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