- non-neoplastic expansile lesion consisting of blood filled spaces separated by connective tissue septa containing bone or osteoid
and osteoclast giant cells
- etiology unknown
- may be primary or secondary;
- an uncommon expansile osteolytic lesion of bone consisting of a proliferation of vascular tissue that forms a lining around blood
filled cystic lesion;
- it develops in metaphyseal region of long bones, pelvis, vertebral posterior elements;
- it commonly involves the proximal humerus, femur, tibia, and pelvis;
- can cause paraplegia when it involves the vertebral posterior elements;
- associated or adjacent Lesions: may be a secondary ABC in 30% of cases
- peak incidence in 2nd decade
- 80% by age 20
- male : female is 1:1.3
- incidence is 0.14 / 100,000
- 1% of bone tumors
- natural history:
- variable Growth Rate
- indolent lesions may spontaneously involute (months to years)
- spontaneous resolution very uncommon in aggressive or secondary lesions
- no documented cases of malignant transformation (telangiectatic osteosarcoma)
- histologic features of ABC;
- radiolucent lesion w/ expanded cortex arising in medullary canal of metaphysis;
- aneurysmal expanded appearance of cortex is contained by periosteum & thin shell of bone;
- marked cortical thinning and erosion and periosteal elevation;
- this lesion rarely penetrates the articular surface or growth plate;
- radiographic differential diagnosis includes:
- simple bone cyst
- central location (unlike ABC)
- absence of expansion
- lack of cortical discontinuity
- giant cell tumor of bone
- occurs in patients over age 20
- lack of expansion
- begin in epiphysis with extension into metaphysis
- more likely to be centrally located
- telangiectatic osteosarcoma
- difficult to distinguish radiographically from an aggressive ABC
- may have a “soap bubble” expansile appearance
- no fluid level on CT/MR
- radiographs demonstrate loss of pedicle of involved vertebrae and some displacement of soft tissues by the mass;
- posterior elements of the vertebrae are a favored location;
- CT scan:
- look for fluid - fluid level (blood / serum): fluid-fluid level may also be seen w/ telangiectatic osteosarcoma;
- ABC has a density of about 20 hounsfield units;
- spine: CT scan shows a cystic lesion not appreciated on the radiograph.
- Bone Scan:
- shows intense uptake in the margin of the lesion, with normal background or decreased uptake in its center;
- Bright on T2 and fat supresssion, intermediate or low signal on T1;
- double density fluid level and septation are also suggestive of ABC, rather than a UBC.
- curettage and bone grafting has a 20-40% recurrence rate: recurrance can be managed w/ more aggressive curettage or excision;
- marginal excision or wide excision w/ bone grafting is preferable;
- adjuvant treatment (w/ curettage)
- adjuvant treatment extends the local zone of necrosis;
- phenol, polymethylmethacrylate, liquid nitrogen, and/or high-speed burr may significantly lower rate of recurrence;
- potential adverse effects, including chemical burns, organ injury, growth arrest, and osteonecrosis;
- in inaccessible areas, such as vertebrae, x-ray therapy is effective;
- w/ pathologic frx, successful resection may be difficult;
- Papagelopoulos PJ, 40 consecutive patients with an ABC of the pelvis and/or sacrum were treated from 1921 to 1996;
- medical records and radiographic and imaging studies were reviewed, and histological sections from the cysts were examined.
- 17 lesions were iliosacral, 16 were acetabular, and 7 were ischiopubic. 7 involved the hip joint, and two involved the SI joint;
- all 12 sacral lesions extended to more than one sacral segment and were associated with neurological signs and symptoms;
- destructive acetabular lesions were associated with pathological fracture in five patients and with medial migration of the
femoral head, hip subluxation, and hip dislocation in one patient each;
- 35 patients who were initially treated for a primary lesion had surgical treatment (21 had excision-curettage and 14 had
- 2 patients also had adjuvant radiation therapy;
- of the 35 patients, five (14%) had a local recurrence noted less than 18 months after the operation;
- of five patients initially treated for a recurrent lesion, one had a local recurrence;
- at the latest follow-up examination, all 40 patients were disease-free and 28 (70%) were asymptomatic;
- in the report by Ramirez, et al., the authors reviewed longitudinally the clinical features, method of treatment, and recurrence rates
of 40 cases of aneurysmal bone cyst in children treated at one institution.
- 29 patients with histologic confirmation of the diagnosis and minimum follow-up of 2 years were included.
- 13 patients were less than 10 years of age, and 16 were in the second decade of life;
- most frequent location of the lesion was the tibia (seven cases).
- patients were treated with curettage, curettage and bone grafting, or resection;
- overall recurrence rate was 27.5%;
- 5 lesions recurred once, and three recurred twice.
- average time before recurrence was 18.7 months.
- recurrence rate dropped after the use of a high-speed bur.
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