- 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;
- in the report by 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 seven were ischiopubic. Seven 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 intralesional excision);
- 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.
Aneurysmal bone cyst in 29 children
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Original Text by Clifford R. Wheeless, III, MD.