Aneurysmal Bone Cysts(ABC’s)

Dr. Ted Scriven

Sept 8, 2008

ABC’s

• Classified as a benign boney lesion

• More specifically, “benign-aggressive”

• Benign-aggressive = marked bone destruction, soft tissue extension or pathologic fractures

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

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

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%)

Clinical Picture

• Mild pain or swelling

• May have neuro deficits with spinal lesions

• Duration = weeks years

• Symptoms may worsen with pregnancy (more blood volume)

Investigations

• Start with thorough Hx & PE

• Xray:– Radiolucent destructive cyst, expands

surrounding cortex “Soap-Bubbles”– Often eccentric, can be central or

subperiostealElevated periosteum

Thin shell

Investigations

• Bone Scan:– 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

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

DDx

• UBC

• Chondromyxoid Fibroma

• Chondroblastoma

• GCT

• Osteoblastoma

• Talengiectatic Osteosarcoma

Pathology

• Gross:– Cavitary w/ blood filled spaces– Surrounded by thin layer of bone & raised

periosteum

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!!)

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

Prognosis

• If 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