Cystic Bone lesions;

1. Aneurysmal Bone Cyst (ABC)
Dr Musa
Registrar
Radiology Dept, FMCK
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2. Outline
• Definition
• Epidemiology
• Pathology
• Clinical Presentation
• Radiological Features
• Treatment and Prognosis
• Differential Diagnosis
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3. Definition
• A true neoplasm: it is an expansile lytic bone lesion
composed of thin-walled blood-filled cystic cavities.
• It represents a reparative process and can be induced
by trauma or tumour.
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4. Epidemiology
• Accounts for 1–2% of primary bone lesions.
• Primarily seen in children and adolescents, usually in
the second decade of life.
• 70 - 80% occurring in patients between 5 and 20 years
of age.
• Equal M : F ratio.
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5. Pathology
• Consist of blood-filled spaces of variable size that are
separated by connective tissue containing trabeculae of
bone or osteoid tissue and osteoclast giant cells.
• They are not lined by endothelium.
• FNAC is usually nondiagnostic, often dominated by fresh
blood
• Although often 10, up to a 3rd of ABCs are 20 to an
underlying lesions: Fibrous dysplasia, Osteosarcoma, Giant
cell tumour, Chondromyxoid fibroma, Non-ossifying
fibroma, Chondroblastoma.
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6. Pathology
• A variant of ABCs, giant cell reparative granuloma
(GCRG) is usually seen in the tubular bones of the
hands and feet as well as in the craniofacial skeleton.
• GCRG are occasionally seen in appendicular long
bones – are known as solid aneurysmal bone cysts.
• Histologically, these two entities are identical.
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7. Clinical Presentation
• Pain: insidious or abrupt due to pathological fracture.
• Palpable lump.
• Scoliosis or neurological symptoms (if it occurs within
a neural arch).
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8. Clinical Presentation
LOCATIONS
• Long bones: 50-60%, typically the metaphysis
• Lower limb: 40%
• Tibia and fibula: 24%, especially proximal tibia
• Femur: 13%, especially proximally
• Upper limb: 20%
• Spine and sacrum: 20-30%
• Esp post. elements, with extension into the vert. body in 40% of cases
• Craniofacial: jaw, basisphenoid, and paranasal sinuses
• Epiphysis, epiphyseal equivalent, or apophysis: rare but imp.
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9. Radiological Features
• XR
• An eccentric lytic expansile intramedullary lesion within long bone
metaphysis (it is occasionally central)
• It extends to the growth plate (but respects it with rare extension
to the articular surface).
• CT
• An egg shell thin cortex with marginal periosteal reaction
• Septal ossification
• Apparent trabeculation
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10. 10
Frontal and lateral Leg/Ankle Radiographs of a 12 years old boy. An expansile lucent lesion is
seen in the metadiaphysis of the tibia with a narrow zone of transition. It does not reach the
growth plate which remains normal. No cortical breach, fracture or periosteal reaction.

11. 12
Axial CT images of the distal ulna
and radius. It demonstrates an
expansile lytic lesion in the distal
ulna with ossified septa and
sclerosed rim.

12. 12
Axial CT and reconstructed images of the proximal Right fibular and Tibia. It demonstrates a
lytic lesion in the proximal fibular that is expansile with egg shell thinning of the cortex with
apparent trabeculation seen in the reconstructed image.

13. Radiological Features
• MRI
• T1WI: cysts of heterogenous intermediate SI +/- a thin sclerotic
margin with hypointense internal septa.
• T1WI + Gad: enhancing internal septa.
• T2WI and PDW: multiple fluid-fluid levels.
• Scintigraphy
• ‘Doughnut’ sign: a photopenic centre with increased peripheral
uptake
• Angiography (DSA)
• Aneurysmal bone cysts are poorly vascular.
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14. 14
Axial T1W MRI of the proximal tibia
and fibular. An expansile
heterogenous lesion of intermediate
signal intensity is seen in the proximal
fibular with hypointense components
(septa) seen within it.

15. 15
Axial T1WI without contrast and T1W C + magnetic resonance imagings of the proximal tibia of a
27 years old female. It reveals expansile heterogenous lesion of intermediate signal intensity with
avid enhancement of the septa (thin arrow) and soft tissue (thick arrow) between the dilated,
blood-filled cystic spaces on administration of contrast.

16. 16
Axial T2W MRI of the
proximal tibia and fibular.
An expansile hyperintense
lesion is seen in the
proximal fibular with
numerous fluid-fluid
levels. There is also a
hyperintense area
surrounding the lesion in
keeping with soft tissue
inflammation.

17. 17
Bone scan images
showing an area of
peripheral uptake with a
photopenic centre giving
the doughnut sign seen
in the neck of the right
fibula suggestive of an
Aneurysmal Bone Cyst.
DDx - giant cell tumour,
simple bone cyst,
chondrosarcoma,
telangiectatic
osteosarcoma

18. 18
A DSA
showing right
and left
vertebral
arteries with
tumour blush
and filling
from
thyrocervical
trunk.
Embolization
of the feeders
did not
reduce the
tumour blush

19. Treatment and Prognosis
• Treatment:
• Surgical curettage with bone grafting
• Radiotherapy
• Percutaneous treatment with fibrosing agents – in isolation or as a
precursor to surgery
• Prognosis
• Spontaneous regression may occur, including following partial
removal, but this is not the typical natural history
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20. Differential Diagnosis
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• On Xray/CT (lytic/lucent lesions)
• Fibrous dysplasia (FD), fibrous cortical defect (FCD)
• Osteoblastoma
• Giant Cell tumour(GCT) or Geode
• Metastases, Myeloma
• Aneurysmal Bone Cyst(ABC)
• Chondroblastoma
• Hyperparathyroidism(Brown tumour)
• Infection or Infarction
• Non-ossifying fibroma (NOF)
• Enchondroma or Eosinophilic Granuloma (EG)
• Simple (unicameral) Bone Cyst
MRI (fluid-fluid bone lesions)
• Chondroblastoma
• Fibrous dysplasia
• Giant cell tumor (GCT) 4
• Osteosarcoma: especially
telangiectatic osteosarcoma

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22. References
• A. Adam, A.K. Dixon, R. G. Grainger, ed (2013). Grainger & Allison’s Diagnostic
Radiology Essentials. London: Churchill Livingstone Elsevier
• Dr Ammar A., (2021). Aneurysmal Bone Cyst
https://radiopaedia.org/articles/aneurysmal-bone-cyst
• Noordin, Shahryar & Ahmad, Tashfeen & Umer, Masood & Allana, Salim & Hilal,
Kiran & Din, Nasir & Hashmi, Pervaiz. (2019). Aneurysmal bone cyst of the pelvis
and extremities: Contemporary management. International Journal of Surgery
Oncology. 4. 1. 10.1097/IJ9.0000000000000071.
• Å. Lindbom, G. Soderberg, H. J. Spjut & O. Sunnqvist (1961) Angiography of
Aneurysmal Bone Cyst, Acta Radiologica, 55:1, 12-16, DOI:
10.3109/00016926109173812
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