An aneurysmal bone cyst is a benign, expansile bone lesion characterized by blood-filled cavities separated by bone or fibrous tissue with osteoclast giant cells. Most patients are under 20 years old, with common locations in the long bones of the lower extremities. The etiology is unknown but may involve genetic translocations. Imaging shows an expansile, osteolytic lesion with possible fluid-fluid levels. Treatment involves preoperative embolization, curettage with bone grafting, or complete resection to prevent the 20-30% recurrence rate associated with partial resection.

1. ANEURYSMALBONECYST

2. DEFINITION
• An aneurysmal bone cyst is a benign, expansile
lesion with blood filled cavities separated by septa
of trabecular bone or fibrous tissue containing
osteoclast giant cells.
• The term derived from its
macroscopic
aneurysmal is
appearance – sponge like tumour
containing numerous giant cells.

3. EPIDEMIOLOGY
•75% of patients are < 20 yrs.
•Anatomic location
o 75% of patients are < 20 yrs.
o 15% in spine
o >60% in long bones (Femur and tibia being most common)
o 51% occured in the lower extremities, 22.5% in upper extremities
o usually in metaphysis
o metatarsal and calcaneus are the most common locations in the foot
o posterior elements of pelvis

4. ETIOLOGY
 The true etiology of ABCs is unknown.
 primary ABC is driven by upregulation of the ubiquitin-specific
protease USP6 (Tre2) gene on 17p13 when combined by a translocation with a
promoter pairing
 most commonly described translocation t(16;17)(q22;p13) leading to juxtaposition
of promoter region CDH11 on 16q22

5. INCIDENCE AND
DEMOGRAPHICS
 ABCis found at anyage
 Around 75%:before 20 yearsand rareafter 30 years
 Female: Male = 2 : 1
 Site - can be found in any bone in the body. The
most common location is the metaphysisof long
bones of lower extremity.
 About 12-30% of the ABCs involve the spine that
represents only 1.4 % of primary vertebral column
tumors.

6.  Spine:
 Most common in the thoracolumbar region
 The cervical spine is involved in 30-41 %.
 As with most benign osseous lesions, 60% of
spinal aneurysmal bone cysts occur in the
posterior elements.
 Half of the casesinvolving more than one
vertebra.

7. PRESENTATI
ON
 Patients usually present with pain, a mass, a pathologic fracture, or
combination of these symptoms in the affected area.
 Neurologic symptoms may develop when involving the nerve, typically in the
spine.
 Other findings may include the following:
• Deformity
• Decreased movement, weakness, or stiffness
• Occasionally, bruit over the affected area
• Warmth over the affected area

8. HISTOLOGY
 Aneurysmal bone cyst consists 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.

9. DEVELOPMENT OF ABC
It follows 3 stages-
Stage Description
I Initial phase Osteolysis without peculiar findings.
II Growth phase •Rapid increase in size of osseous erosion.
•Enlargement of involved bone.
•Formation of shell around central part of lesion.
III Stabilization phase Fully developed radiological pattern.

10. IMAGING
MODALITIES
1. X- ray
2. CTscan
3. MRI
4. Nuclear Imaging
5. Angiography

11. X-RAYAPPEARANCE
• ABC is normally placed in the metaphysis and appears as a
osteolytic lesion. The periosteum is elevated and the cortex is
eroded to a thin margin.
• The expansile nature of the lesion is often reflected by a
"blown-out" or "soap bubble" appearance.
• The lesion rarely penetrates the articular surface or growth
plate.

12. COMPUTED
TOMOGRAPHY
• Cross-sectional CT is the most useful imaging examination, because
it can demonstrate the intraosseous and extraosseous extents of the
lesion.
• CT can be used to determine the nature of the matrix of the tumor,
especially when tumors are in complex locations, such as the facial
skeleton, spine, thoracic cage, and pelvis.
• Spinal CT can demonstrate stenosis of the spinal canal due to
involvement of the posterior elements.

13. FLUID - FLUID LEVEL (NON
SPECIFIC)
FFLresults from separation of 2 fluids of different densities within a cavernousspace
Mnemonic
•
•
•
•
•
•
•
•
G:giant celltumour
O: osteoblastoma
A: aneurysmal bone cyst
T
:telangiectatic osteosarcoma
S: sarcomas
C: chondroblastoma
S: solitary bone cyst
F: fibroxanthoma

14. NUCLEAR
IMAGING
• Demonstration of a solitary lesion on bone scintigraphy helps
distinguish an aneurysmal bone cyst from other bone tumors,
a hemophilic pseudo tumor, etc.
• Radioisotope uptake is increased.
• The common pattern is the accumulation of the tracer in the
periphery of the lesion, with little intensity in the center; this
finding is present in about 65% of cases.

15. Increased radioisotope uptake peripherally with a photopenic center.
"doughnut sign"

17. ANGIOGRAPH
Y
• On angiograms, ABCsare hypervascular lesions .
• This feature is contrary to that of other malignant lesions, such
as osteosarcoma and chondrosarcoma, which have gross
hyper vascularity.
• Hyper vascular regions in aneurysmal bone cysts may affect
the prognosis, because the number and size of the lesions are
positively correlated with the likelihood of lesional recurrence
after treatment.

18. Angiography examination of ABCof a 13-year-old male showed an expansile
lesion involving the left inferior pubic ramus and ischium.

19. DIFFERENTIAL
DIAGNOSIS
• Simple bone cyst
- central location, before epiphyseal fusion
- absence of expansion
- lack of cortical discontinuity
• Giant cell tumor of bone
- occurs in patients over age 20 -40 year
- expansile, eccentric, wide zone of transition
- begin in epiphysis with extension into metaphysis
- involves joints or adjacent bone or soft tissue
• Osteoblastoma
- may have a “soap bubble” expansile appearance
- no fluid level on CT/MR
• Fibrous dysplasia
- ground-glass opacities: 56%
- homogeneously sclerotic: 23%
- well circumscribed lesions
- no periosteal reaction
• Chondroblastoma
- arising eccentrically in the epiphysis of long bone
- internal calcifications can be seen in 40-60% cases
- Sizeranges from 1-10 cm, most are 3-4 cm at diagnosis
• Chondromyxoid fibroma
• - knee joint (2/3)
- well defined radiolucent, eccentric in metaphysis
- marginal sclerosis

20. TREATMEN
T
• Preoperative embolization
• Curettage & bonegrafting
• Complete resection with bone graft
• Radiotherapy
• Steroids & Calcitonin
• The treatment of choice for aneurysmal bone cysts
is gross total resection, which is curative when
feasible.

21. EMBOLIZATIO
N
• Embolization can be used as first-line and the sole
therapy for ABCs.
• Several successful cures after embolization of ABCs
have been reported.
• In addition, embolization is used preoperatively to
decrease intraoperative blood loss and morbidity.

22. SURGER
Y
• Surgically, complete excision of the tumor is the goal
• Aggressive curettage with adjuvant and bone grafting is
prefereable
• Incomplete tumor excision may be associated with
significant rates of tumor recurrence.

23. RADIOTHERAP
Y
• Radiotherapy can be considered in patients with
residual or recurrent tumor.
• ABCs are sensitive to radiation, but the recurrence
rate remains significant despite adjuvant
radiotherapy.
• Usually 26 to 30 Gy are used.

24. PROGNOSI
S
 Recurrence rate 20-30%
 Partial resection or curettage has been
associated with recurrence rates as high as 71%.
 Despite high recurrence rates, cases of
spontaneous regression of ABCs have also been
reported

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