1. Aneurysmal Bone Cysts (ABC’s)
Dr. Ted Scriven
Sept 8, 2008

2. ABC’s Classified as a benign boney lesion
More specifically, “benign-aggressive”
Benign-aggressive = marked bone destruction, soft tissue extension or pathologic fractures

3. Etiology Specific translocation @ 17p13
Can arise de novo, or be associated with another primary:
GCT, chondroblastoma, UBC, osteoblastoma, fibrous dysplasia, nonossifying fibroma, chondromyxoid fibroma, osteosarcoma

4. Increased venous pressure
Etiology
Result from local circulatory abnormality:
Increased venous pressure
Local hemorrhage
Osteolysis
More bleeding
Source of bleeding = capilliaries in cyst membrane
Hemorrhage progresses to destructive lesion

5. Clinical Picture Age: often < 20 Gender: F > M (slight)
Location:
metaphysis or metadiaphysis of long bones (prox humerus, distal femur, prox tibia)
Occasionally iluim or lumbar vertebrae (15 – 20%)

6. Clinical Picture Mild pain or swelling
May have neuro deficits with spinal lesions
Duration = weeks  years
Symptoms may worsen with pregnancy (more blood volume)

7. Investigations Start with thorough Hx & PE Xray:
Radiolucent destructive cyst, expands surrounding cortex  “Soap-Bubbles”
Often eccentric, can be central or subperiosteal
Elevated periosteum
Thin shell

8. Investigations Bone Scan: Angiography:
Diffuse or peripheral tracer uptake
Central area of decreased uptake
Angiography:
Accumulation of contrast throughout +/- hypervascularity of periphery
Absence of viable afferent or efferent vessels

9. Investigations CT
Helps deliniate lesion in areas of complex boney anatomy
MRI
Multiloculated cavities, fluid levels, +/- associated soft tissue mass
Helps to differentiate between ABC & UBC

10. DDx UBC Chondromyxoid Fibroma Chondroblastoma GCT Osteoblastoma
Talengiectatic Osteosarcoma

11. Pathology Gross: Cavitary w/ blood filled spaces
Surrounded by thin layer of bone & raised periosteum

12. Pathology
Micro:
Hemorrhagic tissue with spaces separated by cellular stroma
No endothelial lining or smooth muscle – only lining is compressed fibroblasts
ALWAYS be sure to examine entire speciman and surrounding area (association with other primaries!!)

13. Treatment Curettage & Bone Grafting
Caution: lesion prone to heavy bleeding!
Tourniquet
Pre-op embolization
+/- local adjuvent tx for cavity sterilization:
Phenol, liquid nitrogen, argon
Ressection:
If area is expendable (fibula, metatarsal, etc)
Radiation:
Not routinely used d/t potential for malignant transformation

14. Prognosis If primary: If associated with another primary:
Usually a favourable prognosis
Recurrence:
Rate after curettage = 14 – 34%
Usually within 6/12, rare after 2 yrs
More common in age < 15 yo, centrally located lesions, and when contents not all removed
If associated with another primary:
Classification, treatment and prognosis based on the other (primary) lesion