Radiological approach to malignant bone tumours, differential diagnosis of malignant bone tumours, Malignant bone tumours recall

1. MALIGNANT BONE
TUMOURS
Dr. Soe Moe Htoo

2. CHONDROSARCOMA
• Malignant cartilage-producing tumour
• Generally better prognosis than an osteosarcoma (due to late metastases)

3. Clinical Presentation
• Rare in children
• > 50% of patients over 40 years of age (M:F=1.5:1)
• Most are low-grade tumours found incidentally
• Ccan present with insidious pain, a palpable mass or a pathological
fracture
Location
• pelvis, proximal femur and proximal humerus
• (it is rare distal to the elbow or knee)
• Found within the metaphysis ( epiphyseal extension)

4. Classification:
• Central (intramedullary) vs peripheral
• Primary vs secondary (e.g. arising in a pre-existing bone lesion such as
a central enchondroma or a peripheral osteochondroma)
• Grade I: low grade
• Grade II: myxoid
• Grade III: high grade
• Dedifferentiated: this refers to the development of an adjacent non-
chondroid tumour (e.g. an osteosarcoma, fibrosarcoma, or MFH)
• A major consideration is the differentiation between a chondroma and
a low-grade chondrosarcoma

5. Radiological Features
XR
• well-defined lytic lesion with chondroid matrix
• mineralization (calcification is seen in 75%)
• narrow zone of transition
• slow growth: this allows reactive change with periosteal new bone + bone
expansion + endosteal resorption (endosteal scalloping > ⅔ of the cortical
width suggests a chondrosarcoma rather than a chondroma)
• increased cortical thickness (if the periosteal reaction outweighs the cortical
scalloping)
More aggressive tumours:
• cortical destruction
• should consider dedifferentiation to a more malignant type

6. CT/MRI
• can demonstrate a large extraosseous mass which is commonly seen
with pelvic lesions (which are often radiographically and clinically
occult)
• T1WI: hypointense to muscle
• T2WI: multilobulated high SI lesion
matrix mineralization appears as foci of signal void
• T1WI + Gad: minimal peripheral or septal enhancement (as it is
poorly vascularized)
Scintigraphy
• Chondrosarcoma will demonstrate greater activity than that seen
within the anterior iliac crest

7. Pearls
Suspect the development of a chondrosarcoma within a pre-existing
osteochondroma if:
• There is increased pain or continued growth after skeletal maturity
• There is destruction of part of the calcified cap or ossified stem
• US/CT/MRI: these can assess the cartilage cap – it should be < 5mm
with an osteochondroma (but is often > 20mm with malignant change)

8. Periosteal chondrosarcoma
• This is rare (more common in men)
• Involves the long bones (usually the distal femoral or proximal
humeral metaphyses)
• Good prognosis after resection
XR
A calcified juxta cortical mass with cortical thickening and periosteal
reaction

9. Mesenchymal chondrosarcoma
• Rare
• Affecting younger age group than with a conventional chondrosarcoma
(3rd and 4th decades)
• very much cellular malignant matrix than a normal chondrosarcoma
XR
• Indistinguishable from a central chondrosarcoma
• Often chondroid calcification
• Favourable in ribs and mandible
• Local recurrence and metastases occur early (and more commonly than
with a conventional chondrosarcoma)

10. Clear cell chondrosarcoma
• Rare
• Low-grade tumour with a better prognosis
XR
• Resembles chondroblastoma or chondromyxoid fibroma
• Except it almost always involves the ends of the long bones after
closure of the growth plate (esp. the proximal femur or humerus)
• It has lytic appearance ( a loculated or ‘soap bubble’ appearance)

11. Chondrosarcoma
AP XR showing a mineralized lesion of the fibula
due to low grade chondrosarcoma.
The lesion cannot be radiologically differentiated
from a chondroma.
Chondrosarcoma
AP XR of the proximal humerus showing
a typical low-grade chondrosarcoma with
extensive chondral mineralization and
endosteal scalloping.

12. Dedifferentiated chondrosarcoma
AP XR showing a proximal femoral
chondrosarcoma with an adjacent area of
lytic destruction and a pathological fracture.
Clear-cell chondrosarcoma
proximal femur appearing as a
subarticular, lobulated lytic lesion.

13. Chondrosarcoma of the left ilium Axial CT T2WI show a large extraosseous mass

14. Peripheral chondrosarcoma
(A) AP XR showing an osteochondroma of the distal fibula (arrows).
(B) Axial fat-suppressed T2WI shows a large malignant cartilage cap surrounding
the osteochondroma (arrow) and causing pressure erosion of the adjacent tibia
(arrowheads).

15. Chondrosarcoma of the femur
Coronal T1 and STIR image
large lobulated intramedullary lesion,
particularly hyperintense on STIR

16. OSTEOSARCOMA
• Malignant osteoid-producing tumour
• 2nd commonest primary malignant bone lesion after myeloma
• Commonly a primary central osteosarcoma (75%)
• Secondary to Paget’s disease, postradiotherapy or as a dedifferentiated
chondrosarcoma
Classification:
• Central (conventional high or low grade)
• Intracortical
• Surface (parosteal, periosteal or high grade)

17. Clinical Presentation
• Pain or a palpable mass (usually > 6cm at presentation)
• pathological fracture
• 80% of cases present between 10 and 30 years
• 2nd smaller peak occurring above the age of 40 years which is seen
commonly within the flat bones and vertebrae and usually secondary
to a pre-existing disorder (e.g. Paget’s disease)
Location
• Commonly affects the metaphyseal region of a growing long bone
(50–75% are seen around the knee, and within the distal femur or
proximal tibia)
• it can cross the growth plate with epiphyseal extension (seen in 75% of
cases)

18. Radiological Features
XR
• Moth-eaten or permeative lytic bone destruction arising eccentrically
within the medullary cavity (there can be associated medullary
sclerosis due to mineralized tumour osteoid)
• there is a wide zone of transition
• there can be cortical destruction with an extraosseous mass and cloud-
like matrix mineralization
• Periosteal reaction: a ‘sunburst’ appearance perpendicular to the cortex
• reactive Codman’s triangles are seen at the margins of the lesion
• A solely lytic lesion (13% of cases) may mimic an ABC

19. MRI
• This adds little to the diagnosis but is invaluable for local staging and
assessing any extension (it can demonstrate any intramedullary and
extraosseous extension as well as extension into the adjacent joint or
across an open growth plate)
Scintigraphy
• There is increased uptake

20. Pearls
• It is a highly vascular tumour with early haematogenous metastases to
the lung (with a subpleural location, possible calcification and
potential pneumothorax formation)
• Occasionally there are lymphatic metastases
• ‘Skip metastases’: metastasis within the same bone as the primary (5–
8% of cases)

21. Paget’s sarcoma
• 50% of bone sarcomas arising after 50 years of age are secondary
to Paget’s disease (an osteosarcoma is more common than a
fibrosarcoma or malignant fibrous histiocytoma)
• malignant change is reported in up to 14% of cases of Paget’s
disease (M:F = 2:1)
• it should be suspected if there is a change in pain or a pathological
fracture
• it has a very poor prognosis
Location:
• it is commonly seen within the pelvis or femur
• the spine is usually spared
• XR/CT: Bone destruction with a wide transition zone and a large soft
tissue mass

22. Post-radiation sarcoma
• This is common in treated breast cancer, lymphoma, head and neck cancers
and gynaecological tumours
• it is usually an osteosarcoma with a mean latency period of 15 years
• it commonly occurs within the pelvis and shoulder girdle and has a poor
prognosis
• Criteria for diagnosis: a history of radiotherapy or tumour arising within a
radiation field ▶ a > 3 year latency ▶ a histology different from the original
tumour
• Usually > 30 Gy is required
XR/CT
• Bone destruction,
• soft tissue mass,
• periosteal reaction and radiation change within the underlying bone
MRI
• There are no specific signal characteristics

23. Primary multicentric osteosarcoma
1. Synchronous:
• multiple osteoblastic metaphyseal lesions occurring in children or
adolescents
• poor prognosis
2. Metachronous:
• affects older patients,
• presenting with a solitary lytic or sclerotic lesion within a long or flat
bone
• multiple lesions are seen after more than 5 months
• better prognosis than a synchronous lesion

24. Lytic osteosarcoma
Lateral XR of the distal femur
showing a lytic osteosarcoma.*
Low-grade central osteosarcoma
AP XR of the proximal humerus
showing the lytic, trabeculated pattern.*

25. Pseudocystic osteosarcoma
AP XR of the proximal fibula showing
an expanded, lytic lesion mimicking
an aneurysmal bone cyst.*
Conventional central osteosarcoma
(A)AP XR of the distal femur showing a classical osteosarcoma
with mixed lytic and sclerotic areas, tumour bone formation
in the extraosseous mass (arrow), and a proximal Codman’s
triangle (arrowhead).
(B) (B) AP XR of the proximal tibia showing dense metaphyseal
sclerosis due to an osteoblastic osteosarcoma.*

26. Radiation-induced sarcoma of the left
superior pubic ramus manifest as a region
of lytic bone destruction (arrow) with
underlying radiation osteitis.*

27. Paget’s sarcoma
(A) AP XR of the proximal femur showing Paget’s disease.
(B) Axial T1WI shows an associated large soft tissue mass due
to sarcomatous change.

28. OTHER VARIETIES OF OSTEOSARCOMA
I. SURFACE OSTEOSARCOMAS (4–10%)
1. Parosteal
• This affects an older age group (the 3rd and 4th decades)
• it is slow growing with a good prognosis (which may dedifferentiate)
• it has an equal sex incidence
• Location: The posterior distal femur (60%), proximal humerus or tibia
• Differential: Osteochondroma
Juxtacortical myositis ossificans
(Peripheral ossification in myositis ossificans, central ossification in an
osteosarcoma)

29. XR
• A dense bony mass enveloping the metaphysis with a well-defined
radiolucent line separating the tumour from the normal cortex (it is
only attached to the cortex at its origin)
• it may wrap around the bone
• Satellite bony masses can be seen in the adjacent soft tissue
MRI
T1WI: low SI
T2WI: high SI at the periphery may indicate higher grade or
dedifferentiation

30. 2. Periosteal
• This is an intermediate-grade chondroblastic tumour,
• mean age of presentation of 20 years
• slight male preponderance
• Location: The proximal tibial or distal femoral diaphysis
XR
• A small periosteal lesion with cortical thickening or erosion and a
perpendicular periosteal reaction
• there is rarely nodular matrix calcification
MRI
• T2WI: high SI (due to the chondroblastic nature of the lesion)
• marrow invasion is rarely demonstrated

31. 3. High-grade
• Histologically, same as a conventional central osteosarcoma (but with a
poorer prognosis)
• Radiologically, similar to the periosteal type
• but more aggressive in nature (larger and greater cortical destruction)

32. II. TELANGIECTATIC OSTEOSARCOMA
• This is composed of septated blood-filled cavities (and can mimic an
ABC)
• 4–11% of all osteosarcomas
• Mean age of presentation at 24 years (M:F = 2:1)
• Very malignant, poor prognosis
• Location: Femur, tibia and humerus
XR: Predominantly lytic lesions
CT/MRI:
• Subtle matrix mineralization
• extensive haemorrhage with fluid-fluid levels
• extraosseous extension
• Thick peripheral, septal and nodular enhancement helps differentiate
from an ABC

33. III. SMALL CELL OSTEOSARCOMA
• < 1% of cases
• Similar features to a conventional central osteosarcoma

34. IV. LOW-GRADE INTRAMEDULLARY
OSTESARCOMA
• Well-differentiated lesion
• < 1% of cases
• Mean age of presentation = 34 years
• Slight female preponderance
• Location: The femur and tibia (around the knee)
XR/CT
• Relatively benign appearance (can be mistaken for fibrous dysplasia, osteoblastoma or a low-grade chondroid
tumour)
• Extraosseous extension aids in the differentiation
• 4 patterns:
(1) Lytic with varying degrees of coarse trabeculation
(2) Lytic with little trabeculation
(3) Densely sclerotic
(4) Mixed lytic and sclerotic

35. V. INTRACORTICAL OSTEOSARCOMA
• < 1% of cases
• good prognosis
• presents during the 2nd decade
• (M:F = 2:1)
• Location: The cortex of the femur or tibia
XR/CT
• A small lytic lesion surrounded by a thickened cortex (it can
resemble an osteoid osteoma or osteoblastoma)
• No medullary involvement

36. High-grade surface osteosarcoma of the proximal tibia
(A) AP XR shows a vertical periosteal reaction (arrows) arising from the
medial metaphysis.
(B) Sagittal CT multiplanar reconstruction shows the large associated soft
tissue component. The features are similar to periosteal osteosarcoma, but
more aggressive.*
Telangiectatic osteosarcoma
AP XR of the distal femur showing the
classical ‘iron-filing’-type destruction of
the cortex.*

37. Periosteal osteosarcoma
(A) AP XR showing a spiculated periosteal reaction from the lateral femoral condyle and
nodular matrix mineralization.
(B) Axial fat-suppressed T2WI shows a lobular, hyperintense surface lesion consistent with a
chondroblastic tumour.*

38. Parosteal osteosarcoma
(A) Lateral XR showing a dense, lobulated mass of bone arising from the posterior distal femur.
(B) Axial CT shows a lucent line (arrow) separating the lesion from the underlying cortex.
(C) Sagittal T1WI shows the low SI mass with central intermediate SI (arrow) indicating a region of
dedifferentiation to high-grade tumour. Note also the intramedullary extension (arrowhead).*

39. MALIGNANT FIBROUS HISTIOCYSTOMA (MFH)
• Most common primary malignant tumour of fibrous origin affecting
bone
• Originates from the bone marrow histiocytes
• Approximately 25% arise within a pre-existing lesion (especially
Paget’s disease, post radiotherapy, bone infarction or in relation to a
dedifferentiated chondrosarcoma)
• Rare associations: fibrous dysplasia ▶ non-ossifying fibroma ▶ chronic
oteomyelitis ▶ total hip replacement
• It has a tendency to recur and metastasize

40. • Between 6 - 80 years
• Peak incidence during the 4th decade
• (M:F = 1.5:1)
• Pain and swelling
• Pathological fractures are seen in 20%
Location
• Predominantly the central metaphyses of the long bones (75%)
• Particularly found around the knee
• Humerus, pelvis, spine and ribs are less commonly involved

41. Radiological Features
XR
• A lytic destructive lesion (resembling a metastasis)
• an extraosseous mass may be evident
• central mineralization and sclerotic margins are uncommon
• Periosteal reaction is limited (unless a pathological fracture is present)
• it may extend to a subarticular surface (mimicking a giant cell tumour)
Scintigraphy
• Central photon-poor regions are sometimes seen (occasionally related to a
pre-existing bone infarct)
MRI
• T1WI: intermediate-to-low SI
• T2WI: heterogeneous high SI: T1WI+Gad: variable enhancement
• It may show skip metastases

42. PEARLS
• Multicentric MFH is also recognized
• It may be indistinguishable from a fibrosarcoma
• It has a poor prognosis due to a high incidence of local recurrence and
distant metastases (to the lungs, liver and brain)
• Treatment: Surgical resection (with wide margins) if there has been a
good response to chemotherapy

43. Osseous MFH. AP XR of the proximal femur
showing a moth-eaten destructive lesion with no
characteristic features.*
Malignant fibrous histiocytoma. Anteroposterior (A) and
lateral (B) radiographs show an aggressive lytic lesion of the
distal femoral diaphysis with absent mineralization and
periosteal new bone formation.

44. FIBROSARCOMA
• A malignant tumour of fibrous origin
• Can occur secondary to Paget’s disease, a dedifferentiated
chondrosarcoma, bone infarction, post irradiation, or within a chronic
sinus tract of osteomyelitis
• It presents between 20 and 50 years (M=F)
• Insidious pain and swelling
• Pathological fracture

45. Location
• The long bones (70%): 50% arise within the lower limb (particularly
around the knee)
• it is less commonly seen within the pelvis, humerus or jaw
• Usually metaphyseal and arising eccentrically within the medulla –
often with epiphyseal extension (7% are purely diaphyseal

46. Radiological Features
XR
• ‘moth-eaten’ destruction of bone
• Wide zone of transition in the more malignant tumours
• Cortical destruction (with little periosteal reaction)
• a loculated ‘soap bubble’ appearance
• a small extra-osseous mass (rarely with punctate calcification)
• ‘proximal skip lesions can be seen
• Low-grade lesion: a well-circumscribed lytic lesion with an irregular
lobulated cortex ( sequestrum)
• High-grade lesion: a lytic ill-defined lesion, permeative bony
destruction, extraosseous mass

47. MRI
T1WI: intermediate-to-low SI
T2WI: heterogeneous high SI: T1WI+Gad: variable enhancement
Scintigraphy: Increased uptake
PEARL
• Fibrosarcoma may be indistinguishable from a malignant fibrous
histiocytoma

48. Fibrosarcoma arising in the medulla of the femoral
head and neck. At presentation an ill-defined area of
bone destruction in the medial aspect of the head
and neck is seen, with preservation of the cortex and
no new bone formation.
Fibrosarcoma presenting with a pathological fracture
of the femur. Ill-defined bone destruction, particularly
of the medulla, is associated with very minor
periosteal new bone formation and no sclerosis

49. EWING’S SARCOMA
• A highly malignant neoplasm derived from undifferentiated bone
marrow mesenchymal cells or primitive neuroectodermal cells
• It arises from bone (usually medullary in origin) or extra-skeletally
• Presentation is between 5 and 15 years, with 90% of patients
presenting under the age of 30 years
• (M:F = 2:1)
• Local pain and swelling
• systemic symptoms (including pyrexia and an elevated ESR) are
present if
• there is disseminated disease – this indicates a poor prognosis

50. Location
• Usually involves a single bone
• multiple bone in 10% as Ewing’s sarcoma is one of the few tumours
that readily metastasizes to bone
• Affects diaphysis or metadiaphysis of a long bone (femur and
humerus>pelvic bones>ribs)

51. Radiological Features
XR
• Permeative lytic bone destruction with a wide zone of transition
• rapid extension through the cortex producing a large extraosseous
subperiosteal mass
• Cortical thickening
• occasionally a mixed or mainly sclerotic appearance (especially in the flat
bones)
• rarely a pathological fracture
• ‘Saucerization’: subperiosteal tumour eroding through the outer cortex
• Multilaminar ‘onion peel’ periosteal reaction: this is in keeping with the
periodic activity of the lesion
• Incomplete laminar reaction with marginal Codman’s triangles is more
commonly seen
• ‘Hair-on-end’ periosteal reaction

52. CT
• A large extraosseous component is visualized ▶
• aggressive periosteal reaction
MRI
• T1WI: intermediate-to-low SI compared with muscle
• T2WI: high SI compared with muscle
• T1WI+Gad: enhancement
Scintigraphy: increased FDG uptake

53. Pearls
• Together with an osteosarcoma, it represents 90% of paediatric
primary malignant bone tumours
• There is early spread to the lungs and bones (30% at presentation)
• An extraosseous (soft tissue) Ewing’s sarcoma is rare
• Differential: - Osteomyelitis
- Stress fracture
- Lytic osteosarcoma
- Primary bone lymphoma
- Langerhans’ cell histiocytosis
• Treatment: surgical resection (with wide margins) if there has been a
good response to chemotherapy

54. Primitive neuroectodermal tumour (PNET):
• this is a more differentiated form of Ewing’s sarcoma (although it is
more common in females)
• it includes soft tissue and bone neoplasms that were previously
reported as a peripheral neuroepithelioma, adult neuroblastoma, or a
small cell tumour of the chest wall (Askin’s tumour)
• it cannot be differentiated from a Ewing’s sarcoma on imaging

55. Askin’s tumour
• a rare PNET of the chest wall
• occurring in children and young adults
• presents as a lytic extrapleural mass with rib involvement
• the soft tissue mass tends to be slightly hyperintense to muscle on
T1WI

56. Ewing’s sarcoma. (A) Typical appearance in the proximal humeral metadiaphysis with permeative
marrow destruction, ‘hair-on-end’ and multilaminated periosteal reaction. (B) AP XR of the femur
showing cortical ‘saucerization’ (arrowheads). (C) Coronal T1WI show a large extraosseous mass
(arrows).*

58. CHORDOMA
• Slow-growing locally aggressive neoplasm
• Originate from ectopic cellular remnants of the notochord
• Therefore arises from the midline axial skeleton
• It usually presents between 50 and 70 years of age:
• M = F (< 40 years), M:F = 2:1 (> 40 years)
• Symptoms are usually present for > 1 year before presentation
 pain and local pressure effects:
- Sacral: bladder dysfunction and constipation
- Clival: cranial nerve palsies

59. Location
• Predilection for the sacrococcygeal (50%)
• Clival (40%) regions
• >1 vertebral body involved in 50% of cases
Radiological Features
XR
• A large area of bone destruction with well-defined margins
• occasional amorphous calcification
• destruction of the dorsal aspect of the sella and clivus with spheno-
occipital lesions

60. MRI
• Essential for local staging
• it is almost always associated with a large soft tissue mass
• T1WI: variable SI with areas of high SI (focal haemorrhage or a high
protein content)
• T2WI: a lobulated, high SI mass with internal septations and well-
defined margins with areas of low SI (haemosiderin)
• T1WI + Gad: heterogeneous or septal enhancement

61. Pearls
• It is the 2nd commonest primary spine malignancy,
• accounting for > 50% of sacral tumours

62. Sacral chordoma
AP XR shows a central, lytic destructive
sacral lesions (arrows).*
Sacral chordoma
CT shows predominantly lytic mass
with small foci of calcification.*

63. Sacrococcygeal chordoma
(A) Sagittal T1WI shows the intraosseous extent of
the lesion and the relationship to the anterior pelvic
viscera.
(B) Axial T2WI shows the classical hyperintense,
lobulated nature of the lesion (arrows).*

64. ADAMANTINOMA
• A locally aggressive bone tumour of epithelial origin
• The average age at presentation is 35 years (M:F, 5:4)
• Local pain and tenderness (several years)
• Location 85% occur within the tibia (mostly in the midshaft but also
towards either metaphysis)
• Synchronous involvement of the tibia and fibula in 10%
• initially eccentric but eventually involves the whole depth of the shaft
• occasionally multifocal lesions within the same long bone

65. Radiological Features
XR
• Eccentric involvement of the tibial diaphysis is classical
• Majority  intracortical with geographic cortical destruction (lytic
with a sclerotic lobulated margin)
• ± Internal ossification and septations
• ± Multilocular appearance with satellite lesions
• Extracortical extension is seen in 15% of cases
• Rare findings: (1) Anterior tibial bowing
(2) Moth-eaten destruction
(3) Ground-glass mineralization
(4) Bony expansion

66. MRI
• Ideal for assessing marrow extension (60%), extraosseous extension
and multifocal lesions
• No specific signal characteristics (a lobulated growth pattern is
typical)
• T1WI + Gad: intense uniform enhancement

67. Pearl
• It readily recurs if it is incompletely removed
• Lung metastases are seen in 10% of cases

68. Adamantinoma
AP XR of the tibia showing a
multiloculated, lytic lesion expanding the
cortex.*
Adamantinoma
Sagittal T1WI showing a lobulated
diaphyseal lesion with extension into the
medullary cavity.*

69. MALIGNANT VASCULAR TUMOURS
Haemangioendothelioma
• A low-grade malignant endothelial tumour presenting with local pain
and swelling
• Multifocal in 25% (multifocal disease is a clue to the diagnosis)
• Epithelioid haemangioendothelioma: multifocal but limited to a single
anatomic region in 40%
• Lytic lesion (with a small extraosseous mass in 40%)
XR
• Non-specific
• lytic or mixed lytic and sclerotic lesions
• Rarely seen: periosteal reaction, cortical destruction and extraosseous
extension

70. Angiosarcoma
• A high-grade vascular neoplasm (unifocal or multifocal)
• presents during the 3rd or 4th decades
XR
• Non-specific imaging features (an aggressive lytic destructive process)
• sclerotic lesions, periosteal reaction and pathological fractures are
uncommon

71. Anaplastic sarcoma
• This is highly malignant (sometimes the tissue of origin cannot be
identified)
XR
• A lytic and locally aggressive process with no specific features

72. Angiosarcoma
AP XR of the proximal femur shows
an aggressive, lytic destructive lesion
with no specific features.*

73. BONE METASTASES
• Distant metastases result from venous tumour emboli either from a
primary tumour, regional nodes or other metastases
• they are related to the vascularity of the primary tumour and if there is
access to a valveless venous plexus (e.g. Batson’s vertebral plexus)
• They are common and often multiple (although 9% are solitary)
• they are usually a late occurrence as the lungs will trap most tumour
emboli (unless there is transpulmonary passage of malignant cells or
paradoxical embolism with passage of cells through a patent foramen
ovale)

74. • Unexplained back or limb pain in a patient with a known carcinoma
• a pathological fracture
• Raised alkaline phosphatase
Location
• The commonest metastatic sites are bones containing red marrow –
therefore the axial skeleton (vertebrae, pelvis, proximal femur,
humerus, ribs) is more commonly involved than the appendicular
skeleton
• Thoracic vertebrae: the commonest site for spinal metastases (pelvic
malignancies favour the lumbosacral spine)
• Peripheral metastases: these are rare (50% arise from the bronchus)

75. Radiological Features
• Metastases are commonly multiple and lytic
• osteoblastic change is a tissue response of the host bone rather than
bone tumour production by a metastasis
XR
• This can only visualize lesions > 2cm
• Larger lesions can cause cortical destruction ( periosteal reaction and a
soft tissue mass)
• metastases can have a geographic
• moth-eaten or permeative appearance

76. Scintigraphy
• This is the primary investigation for assessing the whole skeleton
• it is highly sensitive compared to XR but has a poor specificity
(correlation with XR, CT or MRI is required)
• Increased activity reflects increased osteoblastic activity
• Lesions that infarct or stimulate no osteoblastic response (e.g. renal
metastases) will be photopenic as any increased activity relies on a
combination of local blood flow and osteoblastic activity
• ‘Superscan’: this is caused by diffuse osteoblastic metastatic disease
(e.g. breast or prostate) with associated reduced or absent renal activity

77. MRI
• This is more sensitive than XR, and more specific than scintigraphy
• most metastases are located within the medulla
• T1WI: low SI
• T2WI: high SI (a hyperintense halo around a lesion is highly specific)

78. FDG PET-CT
• This is sensitive and specific for metastases
Breast:
• these are mostly lytic (10% are osteoblastic and 10% are mixed)
• it is the commonest cause of osteoblastic metastases in women
• it commonly involves the vertebrae, pelvis and ribs
Prostate:
• these are predominantly osteoblastic (lytic lesions are rare)
• there can be a florid ‘sunburst’ periosteal reaction which can mimic an
osteosarcoma (which are usually rare in this age group in the absence
of Paget’s disease or previous radiotherapy)

79. Lung:
• this commonly affects the axial skeleton (however it is also the
commonest cause of metastases to the hands and feet)
• the majority are lytic (usually a squamous cell or small cell carcinoma)
• focal or diffuse osteoblastic disease can be seen with bronchial
carcinoid or adenocarcinoma
Renal:
• usually lytic and expansile
• marked predilection for the pelvis and lumbar spine
• hypervascular,
• often slow growing
• can be excised if solitary

80. Thyroid:
• Lytic and expansile ( miliary lung involvement)
Colon:
• Lytic (but can be sclerotic and demonstrate calcification)
• they occur in < 7% of patients
Bladder:
• Lytic
• Exuberant periosteal new bone
• Unusual predilection for the lower limbs
Cervix, pancreas, melanoma: Lytic
Uterus, carcinoid, stomach, medulloblastoma, neuroblastoma/Hodgkin’s
lymphoma: Osteoblastic

81. PEARLS
• A solitary lesion in a middle-aged or elderly patient is more likely to
be an atypical metastasis than a typical primary malignant bone
tumour
• A lesser trochanter avulsion fracture in an adult should be considered
pathological until proven otherwise a transverse fracture in a long
bone (especially without significant trauma) may be pathological
• A solitary metastasis can mimic: a primary malignant bone tumour, an
aggressive benign tumour (e.g. giant cell tumour), infection, or Paget’s
disease
• Paediatric skeletal metastases: Neuroblastoma
Leukaemia
Osteosarcoma
Ewing’s sarcoma
Medulloblastoma

83. (A) Whole body 99mTc-MDP bone scintigram (posterior view) showing multiple regions of
increased uptake due to prostatic carcinoma metastases.
(B) Sunburst periosteal reaction. AP XR of the femoral diaphysis showing a spiculated periosteal
reaction mimicking osteosarcoma in a patient with prostatic metastasis.
(C) AP XR showing a mineralized squamous carcinoma metastasisto the radius.*

84. Cold metastasis due to hypernephroma metastasis to the
sacrum. CT (A) shows a lytic destructive lesion of the left
sacrum that also manifests as a ‘cold’ spot on the bone
scintigram (arrow) (B).*
Osteosarcoma metastasis
Coronal STIR image through the posterior pelvis
showing a sclerotic osteosarcoma metastasis of the right
ischium with a hyperintense ‘halo’ (arrow) surrounding
the lesion.*