Approach to benign bone tumors radiologically

1. Dr. Manmohan Bir Shrestha
FOR RADIOLOGY

2. Neoplasm
 A neoplasm is an abnormal mass of tissue, the growth of
which exceeds and is uncoordinated with that of the
normal tissues and persists in the same excessive manner
after cessation of the stimuli which evoked the changes.
 Can be
 Benign
 Potentially malignant
 malignant

3. Epidemiology of bone tumors
 Primary bone tumors are relatively uncommon
 Incidence : Benign>Malignant
 It is likely that benign lesions are underestimated
because they often are asymptomatic and not clinically
recognized.
 In addition, primary bone tumors are outnumbered by
skeletal metastases

4. Classification of Benign Bone Tumors
A. Presumed to arise from skeletal tissue
i. Bony origin
i. Bone island
ii. Osteoma
iii. Osteoid osteoma
iv. osteoblastoma
ii. Cartilaginous
i. Chondroma
ii. Chondroblastoma
iii. Chondromyxoid fibroma
iv. Osteochondroma
iii. Fibrous
i. Fibrous cortical defect
ii. Non-ossifying fibroma (NOF)
iii. Desmoplastic fibroma
iv. Fibromatosis
iv. Giant cell containing
i. Giant cell tumor (GCT)
ii. Aneurysmal bone cyst ( ABC)

5. B. Presumed to arise from other tissues in bone
I. Blood vessels
I. Hemangioma
II. Cystic angiomatosis
III. Hemangiomatosis
IV. Glomus tumor
II. Nerves
I. Neurofibroma
II. Neurilemmoma/Schwannoma
III. Fat
I. Lipoma
IV. Epithelium
I. Implantation dermoid

6. C. Presumed to arise from joints
i. Intraosseous ganglion
ii. Pigmented villonodular synovitis ( PVNS)
iii. Synovial chondromatosis
iv. Lipoma arborescens
D. No known origin
i. Solitary bone cyst (SBC)
E. Non-neoplastic tumors
i. Brodie’s abscess
ii. Hydatid
iii. Hematoma
iv. Infarction
v. Histiocytosis

7. Lytic benign bone tumors
 Osteoid osteoma
 Osteoblastoma
 Chondroma
 Chondroblastoma
 Chondromyxoid fibroma
 Fibrous cortical defect
 Non-ossifying fibroma
 GCT
 ABC
 Hemangioma
 Intraosseous lipoma
 SBC

8. A Bone Lesion!!!
 Is it neoplastic or infective ?
 Is it benign or malignant?
 Is it primary or secondary neoplasm?

9. Approaching a benign bone lesion
 Clinical feature
 May be less useful
 As many lesions present with non-specific features of pain,
swelling or pathological fracture.
 Sex incidence is of little diagnostic value in primary bone
tumors.
 Plain radiograph
 Mainstay of imaging modality
 Views
Antero-posterior, lateral and oblique
 CT Scan
 Can define matrix calcification
 Fractures
 Soft tissue extension

10.  MRI
 Gives idea about varieties of tissues present
 To access the extent of disease
 Intraosseous edema and extraosseous inflammatory
response may be demonstrated
 Pre-op planning / post-op evaluation
 Angiography
 To see tumor vessels
 To see encasement of major adjacent vessels
 To distinguish between tumors, e.g. Osteosarcoma
is highly vascular and chondrosarcoma is
hypovascular

11.  Bone scintigraphy
 Compound – technetium labelled
diphosphonate
 Phases
Blood pool phase
• Vascular lesion e.g. ABC , avascular lsesion e.g.
Cartilage tumors
Delayed phase
 Helps to identify multiplicity of lesions
 To see distant metastases
 Patient is symptomatic ( e.g. bone pain), but no
lesion is identified in plain radiograph or CT
Scan, then Bone scintigraphy can be helpful.

12. Lesion
Age
Multiplicity
Morphology
Location
How we approach

13. Peak age incidence of benign bone neoplasms
 1st & 2nd decades
 Chondroblastoma
 Fibrous cortical defect
 NOF
 Desmoplastic fibroma
 ABC
 SBC
 2nd & 3rd decades
 Osteoid osteoma
 Osteoblastoma
 Chondroma
 Chondromyxoid fibroma
 GCT
 Later
 Intraosseous hemangioma, intraosseous lipoma and glomus tumor

14. Location
Long Axis
Epiphyseal
Metaphyseal
Diaphyseal
Transverse section
-Centric
-Eccentric
GCT
NOF
Fibrous cortical defect
Juxtacortical chondroma
Chondromyxoid fibroma

15. Migrating lesions as skeleton
matures
 SBC
 Fibrous cortical defect
O
O

16. Behavior of a lesion
A. Pattern of destruction
B. Bone response to the lesion
C. Matrix calcification

17. Pattern of destruction/Osteolytic patterns
Geographic Non-geographic/Poorly defined
 Less aggressive
 Can draw the margin of a
lesion clearly
 Usually have a complete rim
of sclerosis/partial / no
sclerosis.
 More aggressive
 Usually malignant
 2 types
 Moth-eaten
 permeative

18. Bone response to the lesion
 Lesion margin
 Periosteal new bone formation

19. Lesion margin
A) Narrow zone of transition B) Wide zone of transition
 Long-standing
 Non-aggressive
 Fast-growing
 Aggressive
 Uncertainty where
the lesion ends and
where the normal
bone begin
 Bone does not have
time to contain such
a lesion

20. Periosteal reaction
Benign Malignant
 Low-grade chronic irritation
allows formation of
normal/near normal cortex
 Cortex will be thick/dense
 Have a wavy/uniform
appearance
 Rapid destruction leads to
cortex appear like lamellated,
amorphous or sunburst like
 Can be seen in benign
conditions as well e.g.
 Infection
 Eosinophilic granuloma
 ABC

22. Patterns of matrix calcification
A. Cloud-like
 Osteoid producing neoplasm
 e.g. osteosarcoma, osteoblastoma
B. Punctate
 Chondroid
 e.g. enchondroma, chondrosarcoma
C. Ground-glass
 SBC
***only 1 benign bone tumor has no matrix - SBC

23. Keys to characterize a lesion
 Age
 Location
 Multiplicity
 Shape
 Size
 X-ray appearance – lytic/dense
 Zone of transition
 Sclerosis
 Periosteal reaction
 Matrix calcification
 Soft tissue involvement

24. I. Bone island
II. Osteoma
III. Osteoid osteoma
IV. osteoblastoma

26. Bone island / Enostosis
 Common benign bone lesion
 Usually seen as an incidental finding
 Constitute a small focus of compact bone within a
cancellous bone
 One of the “ don’t touch lesions”
 Age
 Any age
 May grow in size up to the age of skeletal maturity
 Location
 Can occur anywhere in the skeleton
 some predilection for pelvis, long bones, spine and ribs.

27. Plain radiographic findings
 Single or multiple
 Round or oval
 Always medullary in location
 Has radiating thorn-like spicules with narrow zone of
transition
 Size – usually < 15mm , can be large up to 4 cm
 No periosteal reaction, no cortical expansion
 In diaphyseal bone, the long axis of a bone island
typically parallels the long axis of the involved bone. In
the metaphysis, and other regions, these are typically
more spherical.
 Bone Scan
 Low grade scintigraphic activity

28. Association of Bone Island
 Osteopoikilosis
 Sclerosing bony dysplasia
 Multiple benign bone islands
 Inherited as autosomal dominant disorder
 Mostly affect appendicular skeleton
 Size ranges from 2mm to 2 cm

31. Osteoma
 Seen almost exclusively in bones formed in membrane
 Slow growing, usually asymptomatic, found incidentally
 Location
 Paranasal sinus
 Skull vault
 Mandible
 Size
 Varies, some > 2.5 cm
 Types
 Ivory/dense
 Lacks haversian system
 Spongy
 Resembles normal bone

32. Radiographic features
 Ivory osteomas appear very radio-dense
 Spongy osteomas may demonstrate central marrow
Bone Scan
Increased activity reflects the size of the lesion.

33.  Complications
 Growth within PNS can cause mucocele
 Growth from inner table of skull may produce raised
intracranial pressure
 Association – “Gardner syndrome”
 Multiple osteomas of skull, mandible and long
bones
 Familial adenomatous polyposis
 Soft-tissue tumors of connective tissue origin

34. Ivory osteoma in roof of right orbit

35. Mandibular osteoma

36. Mandibular osteomas in Gardner syndrome

38. Osteoid osteoma
 Age
 10-35 yrs.
 Sex incidence
 M:F = 3:1
 Clinical feature
 Typical history of localized, intermittent bone pain of several
weeks or months, occurring specially at night, with dramatic relief
by NSAID’s
 Location
 Long bones of limbs, majority in femur & tibia
 Can occur anywhere
 In spine, occurs in posterior elements.
 (careful scrutiny of the neural arches at the apex of the concavity
of scoliosis)

39. Pathology
 An osteoid osteoma is composed of three
concentric parts-
I. nidus
I. meshwork of dilated vessels, osteoblasts, osteoid
and woven bone
II. may have a central region of mineralization
II. fibrovascular rim
III. surrounding reactive sclerosis
***The nidus releases prostaglandins (via Cox-1 and
Cox-2) which in turn result in pain.

40. Plain radiograph & CT features
 A round or oval radiolucency with a sclerotic margin
and contains a small dense center, known as nidus
 Solid periosteal reaction with cortical thickening
 Size – usually < 2 cm
 Can be multifocal

41. Bone scan
 Most important means in cases of medullary osteoid
osteoma, where radiographs remain normal
 Also important in any young patients with bone pain
and normal radiographs
 Findings
 Intense focal area of increased activity surrounded
by less intense activity from the reactive sclerosis.
 Evident in blood-pool image and persists in delayed
image.

42. Case of 10 yrs. old with left hip pain

43. Differentials
 Osteoblastoma (>2cm)
 Stress fracture – that causes chronic cortical
thickening
 Chronic osteomyelitis
 Area of radiolucency more irregular
 Sequestra are irregular or linear in shape,
differentiating from central nidus of osteoid
osteoma

45. Osteoblastoma
 Similar in histological characteristics as osteoid osteoma but usually
larger
 Less common than osteoid osteoma
 Age
 80% of patients under the age of 30
 In 2nd and 3rd decades
 Clinical feature
 Long insidious history of pain, often worsening at night
 Not relieved by NSAID’s
 Limitation of movement
 Location
 Spine ( posterior element), flat bones
 Metaphysis and distal diaphysis of long bones.
 Pathology
 Larger than osteoid osteoma
 Irregular in shape, friable and hemorrhagic
 Abundant osteoid tissue and many thin-walled capillaries

46. Plain radiograph and CT features
 Size = 2-10cm
 Radiolucent lesion
 Margin – irregular but sharply demarcated
 Surrounding sclerosis – varies but can be profound
 Can cause cortical expansion and thinning
 Calcification or ossification of osteoid tissue –
punctate or amorphous
 Sometimes, lesion can be aggressive with soft tissue
masses containing calcification and ossification
 Bone scan
 Active both in blood-pool and delayed phase

47. Osteoblastoma in D11 in 7 yrs. Old boy

48. Osteoblastoma in femur

49. I. Chondroma
II. Chondroblastoma
III. Chondromyxoid
fibroma
IV. Osteochondroma

51. Chondroma/Enchondroma
 Relatively common benign tumor
 Single/multifocal
 Usually central medullary
 Age
 Childhood to adulthood, peak incidence = 10-30 years
 Clinical feature
 Rarely symptomatic
 Patient may admit localized hard swelling for many years
 May be complicated by pathological fracture
 Location
 50% in hands – commonly in phalanges, less commonly in
metacarpals
 10% in small bones of feet
 20% - long bones
 20% - flat bones – pelvis, scapula and vertebral bodies.

52. Plain radiograph & CT scan features
 Cartilaginous tissue is not radiopaque
 Radiolucent lesion
 Expansion and thinning of overlying cortex
 No periosteal reaction in the absence of
fracture
 Zone of transition is narrow and sclerotic
 Endosteal scalloping = +-
 Flecks of calcification within the lesion
 usually purely lytic in phalanges, in other
locations, enchondromas are expansile, with
characteristic “rings and arcs” calcifications.

53. MRI
 T1
 Low to intermediate signal
 T2
 typically of background intense high signal
(high water content of hyaline cartilage matrix)
 they can be focal regions of signal drop out where calcification
present
 Post-contrast
 Variable enhancement

54. In phalanx

55. Special type- Juxtacortical chondroma
 Rare
 Usually in young adults and
related to the cortex of a long
bone and phalanges
 Radiologically –
 Well-defined soft tissue mass with
calcification
 Bordered by thin, incomplete shell
of overlying bone
 Pressure erosion causes scalloping
of underlying cortex
 Variable sclerotic reaction

56. Associations
 Ollier disease
 non-hereditary, sporadic, skeletal disorder
characterized by multiple enchondromas that
are principally located in the metaphyseal
regions.
 Maffucci’s syndrome
 Rare association of dyschondroplasia with
cavernous hemangiomas in soft tissues

57. Differentials
A. Implantation dermoid cyst – in hands
B. Medullary bone infarct
A. Curvilinear peripheral calcification in the infarct

59. Chondroblastoma
 Rare
 Characteristically occur in epiphyses of apophyses
of long bones in young patients
 Age
 <20yrs
 Sex prevalence
 Slight male predominant
 Location
 Most tumors occur in epiphyses of long bones, specially around
the hips, knees or shoulders
 Also occur in apophyses

60. Plain radiograph and CT Scan features
 Well-defined oval lucent lesion
 Size = 1-10 cm
 Position- eccentric in the epiphyses
 Margin- thin sclerotic rim
 Cortical expansion = +-
 Periosteal reaction = +-
 Internal calcification = about quarter of cases =
stippled calcification

61. MRI
 Ideal for evaluating transphyseal or transcortical
expansion
 To see bone marrow & soft tissue edema
Bone scan
 Increased activity in blood-pool phase

62. Chondroblastoma in proximal tibia

63. Chondroblastoma in distal femur

64. Differentials
 Osteomyelitis – Brodie’s abscess (same location)
 Giant cell tumor – older age group

66. Chondromyxoid fibroma
 Predominantly chondroid, but contains myxomatous
tissue and giant cells as its name tells
 Age
 2nd and 3rd decades
 Location
 2/3rd around the knee joint – specially proximal tibia
(metaphyseal, may extend to epiphyseal line)
 Can occur in flat and short bones

67. Plain radiograph and CT Scan features
 Lobulated radiolucent, eccentric lesion
 Well-defined margin with surrounding sclerosis
 Presence of septations
 No periosteal reaction
 Calcification very uncommon
 Sometimes, peripheral bony margin very hazy and
poorly defined , appearing aggressive
 CT is helpful to delineate a cortical margin in the
expanded soft-tissue mass
 Bone scan
 Increased activity is usually localized to the reactive sclerosis
rather than to the lesion itself

68. In Ulna

69. Differentials
 NOF – younger age group
 Chondroblastoma – younger age group
 ABC = ill-defined endosteal margin

71. Osteochondroma/Exostoses
 Relatively common
 Osseous outgrowth arising from bony cortex
 Single/multiple
 Capped by cartilage
 In long bones, grows away from the metaphyses to the diaphysis,
i.e. away from the joint – typical characteristic
 Age
 Develop during childhood
 Can present at any age
 Location
 Lower limb =50%
 Upper limb = 10-20%
 Flat bones like scapula and pelvis
 Types
 Sessile – usually in pelvis
 pedunculated

72. Plain radiograph & CT scan features
 In long bones, in the metaphysis & grows away from
the joint
 Size – varies, can be as long as 10 cm
 Pedunculated type – cortex of lesion continuous with
the underlying bone and medullary cavity merging
through the cortical defect
 Cartilage cap best seen in CT
 As age increases – calcification increases ( punctate or
curvilinear)
 Growth ceases after skeletal maturation
 Sessile type in flat bones may resemble cauliflower

73. Osteochondroma - pedunculated

74. Sessile osteochondroma in ilium

75. Differential
 Supracondylar/Supratrochlear/Avian spur
 Anatomic variant
 In distal antero-medial humeral cortex
 About 5 cm above the elbow joint
 Directed towards the elbow joint

76. Hereditary multiple exostoses/ Diaphyseal aclasis
 Autosomal dominant
disorder
 Multiple
osteochondromas
 Diagnosed by the age
of 12 years
14 yrs. old

77. Malignant transformation of cartilage
forming tumors
 Tumors that can transform
 Chondroma
 Osteochondroma
 Common if location – in long and flat bones
 More common in diaphyseal aclasis
 When to suspect transformation??
 Recent increase in pain
 Alteration of radiological appearances on serial films
 Late development of pathological fracture
 Cortical destruction
 Soft tissue mass

78. i. Fibrous cortical defect
ii. Non-ossifying fibroma
iii. Desmoplastic fibroma
iv. Fibromatosis

80. Fibrous cortical defect
 Extremely common
 Usually discovered by chance
 Histologically identical to NOF
 Age
 Typically occur in children
 2-15 years
 Location
 Occurs in distal femur, ends of tibia
 Metaphysis or diametaphyseal regions
 Less frequent in upper limbs

81. Radiographic features
 Sharply defined lucent intracortical lesion
 They are blister-like cortical expansion
 Size = small than 2-3 cm
 May appear only lucent lesion when on frontal view
 Have fine sclerotic margin
 Increasing skeletal maturity = increasing sclerosis =
migrates to diaphysis = involutes
 No periosteal reaction
 Not reach medullary cavity

82. In metadiaphyseal region of distal tibia

83. Differentials
 NOF
 Osteoid osteoma
 Stress fracture

85. NOF
 Most common benign fibrous lesion
 Similar to fibrous cortical defect, but much larger and
occurs in slightly older age
 they spontaneously heal, being gradually filled in by
bone
 Age
 10-20 yrs.
 Location
 Vast majority around the knee joint.
 Femur being the commonest

86. Radiographic features
 Sharply defined lobulated radiolucent lesion in the
metadiaphysis, often eccentric
 Larger than fibrous cortical defect
 Have thin sclerotic rim
 Cortex – intact and thinned
 No periosteal reaction
 Skeletal matures – moves toward diaphysis – gradually
involutes by filling of bone
 Differentials
 SBC
 Monostotic fibrous dysplasia

87. In distal tibia

88. NOF in humerus, 15 yrs. old

90. Desmoplastic fibroma
 Extremely rare
 Exhibits dense fibrous tissue
 Do not metastasize but locally aggressive
 Age - usually in young adults
 Clinical feature
 Constant pain
 Lesion is often tender

 Location
 Metadiaphysis of long bones
 Pelvis and spine
 Pathology
 Abundant collagenous stroma
 Fibroblasts, myofibroblasts & mesenchymal cells

91. Plain radiograph & CT Scan features
 Tend to be large, solitary and destructive
 Expanded irregular sclerotic margin
 Trabeculated pattern
 Widening of host bone due to periosteal new bone
formation,

92. Desmoplastic fibroma

93.  GCT
 ABC
 Brown tumor of hyperparathyroidism
 Chondroblastoma
 Chondromyxoid fibroma.

95. GCT/Osteoclastomas
 Name coming from its histological picture
 GCT containing richly vascular tissue with spindle cells
and numerous giant cells
 It neither forms bone nor cartilage
 Locally aggressive
 Can recur after excision
 Age
 20-40 years
 3% develop in immature skeleton
 Location
 around the knee: distal femur and proximal tibia: 50-65%
 distal radius: 10-15%
 sacrum: 4-10%
 vertebral body: 5-10%

96. Plain film & CT features
 A lucent lesion typically situated beneath the articular
surface
 Eccentric
 Narrow zone of transition
 ‘soap-bubble’ pattern of calcification
 No sclerotic margin
 overlying cortex is thinned, expanded or deficient
 Soft-tissue mass may be present
 No calcification or ossification until complicated by
fracture
 CT Scan & MRI
 To delineate soft tissue extension
 Bone scan
 Increased activity in blood-pool phase

97. 35 yrs. Old male patient

98. 20 yrs. old male

100. ABC
 “Aneurysmal” name – is derived from macroscopic
appearance of a blood-filled, expansile, sponge-like
tumour containing numerous giant cells
 May arise in association with NOF, fibrous dysplasia
and chondromyxoid fibroma
 Age
 Children and adolescents.
 80% before 20 yrs. of age
 Location
 Long bones 50-60%, typically metaphysis, Lower>Upper limb
 Spines and sacrum = 20-30%
 Craniofacial – jaw, basisphenoid and pns

101. Plain film features
 An expansile lytic lesion
 Size = 2-20 cm
 Zone of transition – can be ill-defined
 Thin sclerotic margin
 Cortical breach and soft tissue extension
CT & MRI
 To delineate soft tissue extension
 Shows characteristic fluid-fluid levels (representing areas of
blood of variable ages)
 ***Other benign lesions with fluid-fluid levels
 GCT
 Chondroblastoma

102. ABC in Tibia

103. ABC in Humerus, 10 yrs. old
Coronal T2 fat sat
Axial PD

104. ABC GCT
Age Before epiphysis fusion
80% = <20 years
After epiphysis fusion.
20-40 years
Location Long bones
Spines and sacrum
craniofacial
Predominantly in long
bones around knee and
wrist
Extension Central and in
metaphysis, do not reach
articular surface
Eccentric and
subarticular in position
Differential of ABC in long bone is GCT
Differentials of ABC in spines – Osteoid osteoma and Osteoblastoma
(bone-forming nature differentiates these)

105.  Hemangioma
 Cystic angiomatosis
 Hemangiomatosis
 Glomus tumor

107. Intraosseous Hemangioma
 Typically solitary
 Frequent incidental finding in MRI of spine
 Age
 10-45 years
 Types
 Cavernous – with large thin-walled vessels, occurring particularly in
spine and skull
 Capillary – spread in a sunburst pattern
 Location
 50% spine
 50% skull and long bones

108. Plain film and CT features
 Osteolytic lesion with a trabecular pattern
 No expansion in spine
 Can cause cortical expansion in skull and long bones
with thin rim of sclerosis
 In long bones, osteolytic lesion may have soap-bubble
appearance with stippled radiodensity
 Can affect posterior elements of vertebra

109. MRI
 T1WI
 High signal if fat rich
 Intermediate to low signal if fat poor
 T2WI
 High signal
 Post-contrast
 Enhancement often present

110.  Corduroy sign
 Vertical thickened trabeculae
seen in coronal/sagittal view
 Trabeculae are visible as they
are surrounded by fat
marrow or vascular lacunae
 Polka-dot sign
 Thickened trabeculae seen in
axial view
Appears white on black in CT
Black on white in MRI

111. 55 yrs. old female , skull vault hemangioma

113. Glomus tumor
 Rare, highly differentiated vascular tumor
 Age
 4th and 5th decades
 Clinical feature
 Extremely painful, tender and sensitive to cold
 Location
 Terminal phalanx, particularly subungual portion
 Pathology
 branching vascular channels
 aggregates of specialized glomus cells

114. Plain film features
 Lucent lesion with extremely sharp margin
 May show osseous erosion or thinning of adjacent
cortical bone
 Bone Scan
 Increased activity in early phase and blood-pool phases

115. Complaints of small painful swelling
on dorsum of index finger
Plain film Sagittal PDSagittal T1WI

117. Intraosseous Lipoma
 Extremely rare
 Age
 Wide range = 5-85 years
 Usually detected in 4th-5th decades
 Location
 Lower limb = 75% ( metaphysis)
 Calcaneum>femur>tibia>fibula
 Upper limb
 Skull and mandible
 Spine & pelvis
 Ribs

118. Plain radiograph feature
 Expansile radiolucent lesion with sharply defined
sclerotic margin
 No periosteal new bone formation
 Within calcaneum, lipoma has characteristic
appearance, osteolytic lesion with a central focus
of ossification
 CT & MRI
 Can be homogenous fat content
 Fatty lesion with central necroses, central
calcifications or ossifications
 Fatty lesion with multiple central necroses, central
calcifications or ossifications

119. Calcaneal lipoma
Differentials for intraosseous lipoma – SBC and Bone infarct

120.  Simple bone cyst/
 Unicameral bone cyst/
Solitary bone cyst

121. SBC Always unilocular
 Found incidentally, more than half present due to a pathological
fracture
 Age
 1st and 2nd decades
 Can occur after skeletal maturation
 Sex incidence
 M:F = 2-3:1
 Location
Typically intramedullary in long bones
In childhood, near growth plate, then migrates to diaphysis, then involutes
Proximal humerus>Proximal femur>Other long bones
Calcaneum & Talus ( after skeletal maturation)
 Pathology
 Cyst contains clear liquid unless there has been contamination by bleeding
following a fracture .
 Cyst is lined by a thin layer of connective tissue.

122. Plain radiograph & CT features
 A central radiolucent lesion in metadiaphysis is
characteristic
 Cortex may be thinned and expanded
 Sclerotic margin
 A serpiginous margin (by prominent ridges of bone)
may cause the cyst to appear multilocular.
 No periosteal reaction unless a fracture has occured
 No internal calcification

123. Fallen fragment sign
 If there is fracture through this lesion, a dependent
bony fragment may be seen, and this is known as the
fallen fragment sign.
 Differentials for SBC –
 ABC
 GCT
 Eosinophilic granuloma

125. SBC with fallen fragment sign

126. Simple bone
cyst
Aneurysmal bone cyst
Site Metadiaphysis Typically in the metaphysis
Bone scan No abnormality
develops
Rich increase in vessels and early
venous filling
CT & MRI
(fluid-fluid
levels)
Absent Are the characteristic
Association Absent May be with non-ossifying
fibroma, fibrous dysplasia and
chondromyxoid fibroma
Cyst Clear liquid and
always
unilocular
Contains blood with giant cells
and multilocular.

127. Simple bone
cyst
Giant cell tumor
Age Before
epiphyseal
fusion .
Childhood and
early adolescent
Majority between 20-40 yrs of
age. Only 3% in immature
skeleton.
Anatomical
distribution
Proximal
humerus
proximal femur
Other long
bones rarely
calcaneum
Majority occurs around knee and
wrist
Extension Do not extends
to the articular
surface and is
central
Extension is subarticular and
eccentric in nature.

128. Simple bone cyst Eosinophilic
granuloma
Site Proximal humerus
Proximal femur
Other long bones
Calcaneus
Any bone may be affected
commonly –skull
- pelvis
-femur.
Clinically Asymptomatic often
presents with
pathological fracture
Pain, swelling and mild
fever.
Histology Cyst filled with clear
liquid
Contains eosinophilic
infiltration.

129. Characterizing a bone lesion
 Age
 Location
 Multiplicity
 Shape
 Size
 X-ray appearance – lytic/dense
 Zone of transition
 Sclerosis
 Periosteal reaction
 Matrix calcification
 Soft tissue involvement