Aneurysmal Bone Cyst

Aneurysmal Bone Cyst

G. Petur Nielsen, MD

Andrew E. Rosenberg, MD

Radiograph shows an eccentric diaphyseal tumor of the ulna extending into the soft tissues that is demarcated by a rim of bone.

Aneurysmal bone cyst arising in the diaphysis of the fibula consists of hemorrhagic cystic spaces with thin fibrous septae. The cyst has broken through the cortex and extended into adjacent soft tissue.



  • Aneurysmal bone cyst (ABC) Definitions

  • Destructive, expansile benign neoplasm of bone characterized by multiloculated, blood-filled cystic spaces

  • ABCs are classified into primary and secondary variants

    • ABC, not otherwise specified refers to a primary de novo tumor and accounts for approximately 70% of cases

    • Secondary ABC is defined as neoplasm that contains areas resembling aneurysmal bone cyst, which arise in background of other types of benign or malignant bone tumors



  • Recent cytogenetic and molecular studies demonstrating t(16;17) strongly suggest that primary ABC is neoplastic

    • This translocation results in CDH11-USP6 gene fusion transcript

    • All ABCs with cytogenetic t(16;17) show genomic CDH11 and USP6 rearrangement by FISH

      • ABCs showing only 17p13 rearrangements show rearrangement of USP6 locus whereas those that show 16q22 rearrangement show rearrangement of CDH11 locus only



  • Age

    • Affects all age groups with most cases (80%) occurring in 1st and 2nd decades of life

  • Gender

    • Equal male:female ratio


  • Metaphysis of long bones of upper and lower extremities

  • Posterior elements of vertebra

  • Small bones of hands and feet

  • Craniofacial skeleton

  • May also arise in flat bones such as pelvic and scapula bones


  • Pain and swelling

  • Tumors in spine can cause nerve compression and neurologic symptoms Treatment

  • Curettage or en block resection Prognosis

  • Recurrence rate low: Usually recur shortly after treatment (within 6 months)

  • Spontaneous regression may occur following incomplete removal

  • Rare reports of apparent malignant transformation of ABC have been described

    • Unclear whether these tumors represent malignant transformation or ABC-like change in preexisting sarcoma


Radiographic Findings

  • Lytic, expanded lesion; expansion may be marked

  • Periphery of lesion usually delineated by shell of reactive bone though this may not be visible on radiographs

    • Thickness of shell inversely related to rate of expansion

  • Usually arises eccentrically within long bones

MR Findings

  • Multiloculated and may demonstrate internal soft tissue septa and characteristic fluid-fluid levels

  • Exhibit only modest levels of enhancement

CT Findings

  • Cystic, expansile, and radiolucent

Bone Scan

  • Hot on bone scan


General Features

  • Multiple blood-filled cystic spaces separated by thin, tan-white septa

  • More solid tan-white areas can also be seen

    • Either represents a solid portion of ABC wall or primary lesion that has developed secondary ABC-like change

    • Solid areas within ABC should be thoroughly sampled to identify presence of possible underlying primary neoplasm


Histologic Features

  • Uniform plump fibroblasts that may be mitotically active

  • Scattered multinucleated osteoclast-like giant cells

  • Reactive woven bone

    • Lined by osteoblasts and follows contours of fibrous septa of cyst walls

  • Approximately 1/3 of cases contain matrix known as “blue bone”

    • Infrequently seen in other types of bone tumors

  • Necrosis uncommon unless there has been a pathologic fracture

  • Solid ABC lacks blood-filled cystic spaces and is composed of elements that compose cyst wall

    • May be hypercellular, mitotically active, and contain woven bone



  • Cytogenetic studies have shown t(16;17)


Giant Cell Reparative Granuloma

  • Giant cell reparative granuloma and solid component of ABC are histologically identical

    • Giant cell reparative granulomas typically arise in small bones and in jaw and do not demonstrate cytogenetic abnormality seen in ABC Telangiectatic Osteosarcoma

  • Can grossly simulate ABC

    • Fibrous septa in telangiectatic osteosarcoma contain overtly malignant neoplastic cells with marked pleomorphism and easily identifiable mitotic figures Secondary Aneurysmal Bone Cyst

  • Variety of benign and malignant bone tumors can develop secondary ABC-like changes

  • ABCs need to be carefully sampled histologically to exclude any underlying lesion, as tumor will behave as the primary tumor

  • Secondary ABC does not have cytogenetic abnormalities present in primary ABC


1. Oliveira AM et al: Aneurysmal bone cyst: a neoplasm driven by upregulation of the USP6 oncogene. J Clin Oncol. 24(1):e1; author reply e2, 2006

Image Gallery

Imaging Features

(Left) X-ray of the distal femur shows an aneurysmal bone cyst (ABC) extending into the posterior soft tissues. The intraosseous component is purely lytic and in the soft tissues; it appears mineralized due to the overlying rim of periosteal bone. (Right) T2-weighted MR shows an ABC composed of cystic spaces partitioned by thin membranes. Multiple fluid-fluid levels image represent layering of the cyst components with the heavier (presumably cellular) elements settling to the dependent parts of the lesion.

(Left) Axial CT scan through an ABC shows that it has eroded the cortex and is demarcated from the soft tissues by partially mineralized periosteal new bone image. The tumor has mixed signal intensity. (Right) AP radiograph of the knee in a skeletally immature child shows a lytic lesion of the proximal tibial metaphysis extending to the growth plate. The bone margin appears relatively well demarcated and slightly sclerotic image. The soft tissue margin is difficult to identify.

(Left) Coronal reformatted CT scan shows an ABC that has a sclerotic sharp bony margin image and has eroded the cortex. (Right) T2-weighted MR of an ABC demonstrates a fluid-fluid level that extends across the entire width of the lesion, indicating that there is no solid component. Fluid levels can be seen on CT scans but are best visualized on MR. This may be due to better soft tissue contrast afforded by MR or the fact that an MR examination takes longer to perform, facilitating settling of the cyst contents.

(Left) Reformatted CT scan of an ABC of the tibia shows an eccentric lytic lesion that has a well-formed margin image and a thin shell of periosteal bone image. Fluid components are identified as low-attenuation areas image, but fluid levels are absent. The patient was supine for this examination, and coronal reformations do not demonstrate fluid levels. (Right) Axial T2-weighted MR of an ABC of the tibia shows multiple fluid levels image. The tumor is well circumscribed.

(Left) AP radiograph of a teenager (the growth plate is open image) shows an eccentrically located (cortically based) aneurysmal bone cyst of the medial tibia. Laterally, the cyst has a sclerotic rim image whereas medially, it is surrounded by periosteal bone formation image. (Right) Axial T1-weighted, fat-suppressed, contrast-enhanced MR of a cortically based aneurysmal bone cyst shows that the lesion exhibits rim enhancement image within the cyst walls.

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Jul 6, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Aneurysmal Bone Cyst

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