Aneurysmal Bone Cyst

What is an aneurysmal bone cyst?

An aneurysmal bone cyst is a benign, blood-filled lesion in the bone that tends to expand or grow. While it is referred to as a cyst, it is a true benign bone tumor surrounded by a thin wall of bone. Aneurysmal bone cysts (ABCs) can occur in any bone, but are most commonly found around the knee, pelvis or spine.

Even though they are not cancerous, aneurysmal bone cysts tend to grow quickly, and treatment is recommended.

ABCs occur slightly more frequently in females than males and there is a 10-15 percent recurrence rate with treatment.

Aneurysmal bone cysts may occur spontaneously, or be a secondary reaction to another bony growth elsewhere in the body. Research has revealed a high incidence of accompanying tumors (specifically chondroblastoma and giant cell tumors) in 23 to 32 percent of patients with an aneurysmal bone cyst.


While the cause of aneurysmal bone cysts is currently unknown, recently ABCs have been linked to a mutation of the ubiquitin specific peptidase 6 (USP6) gene on chromosome 17.

Researchers at Children’s Hospital of Philadelphia are currently working to better understand the genetic mutation, learn when it develops, and discover how it may affect a child’s development.

Signs and symptoms

The symptoms of an aneurysmal bone cyst can include:

  • Pain
  • Swelling
  • Stiffness
  • Deformity in the area of the growth
  • The feeling of warmth over the affected area
  • Decreased range of motion, weakness or stiffness

Testing and diagnosis

If an aneurysmal bone cyst is not treated it can cause pain, fractures, disrupt growth and cause neurological symptoms.
At Children’s Hospital of Philadelphia, our clinical experts use a variety of diagnostic tests to diagnose aneurysmal bone cysts, including:

  • X-rays, which produce images of bones.
  • Magnetic resonance imaging (MRI), which uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs, soft tissues, muscles, ligaments and other structures within the body. Your child is exposed to no radiation during an MRI.
  • Computed tomography (CT) scan, which uses a combination of X-rays and computer technology to examine bones and produces cross-sectional images ("slices") of the body.
  • EOS imaging, an imaging technology that creates 3-dimensional models from two flat images. Unlike a CT scan, EOS images are taken while the child is in an upright or standing position, enabling improved diagnosis due to weight-bearing positioning.
  • Angiography, a radiograph-type X-ray test which reveals the inside of blood vessels and organs.
  • Needle biopsy, which is a procedure where a doctor places a small needle through the skin and into the lesion to withdraw a small sample of the abnormal tissue. The tissue is analyzed to confirm any findings.

In addition to diagnosing the specific type of growth your child may have, these tests will also help determine the size and location of the tumor. All of this information is crucial in determining the best treatment options for your child.


There are many treatment options available for bone and soft tissue tumors, and some children will need a combination of these therapies. At CHOP, experts at the Bone and Soft Tissue Tumor Program take a team approach to treatment. Orthopaedic, oncology and other specialists collaborate to provide your child with individualized care and the best possible outcomes.

Our program is led by Kristy L. Weber, MD, and Alexandre Arkader, MD, nationally renowned surgeons who specialize in treating bone and soft tissues tumors, limb-sparing surgery and reconstructive surgery.

Treatment for aneurysmal bone cysts may include:

  • Intralesional curettage, which involves scraping out the bone to completely remove the tumor and all cyst lining
  • Intraoperative adjuvants — such as cryotherapy (liquid nitrogen), phenol (a chemical) or cauterization (burning the tumor bed) — which are used to remove microscopic tumor cells
  • Bone grafting, a surgical procedure to replace missing bone with artificial graft material or cadaver bone

Depending on the size and location of aneurysmal bone cyst removed, your child may be able to return home that day or may spend one night in the Hospital.

In certain conditions, it is recommended to use nonsurgical techniques to treat the tumor. When the ABC is in a hard-to-reach place, an intralesional injection or serial embolization — performed by an interventional radiologist — is often the best treatment.

Your child’s clinical team will recommend the best treatment for your child’s individual situation.

Surgical safety

Though surgery for tumors is highly effective, we understand that any surgery can be a stressful experience for children and families. At CHOP, we offer a wealth of resources about how to prepare your child for surgery and what to expect during surgery.

Additionally, we employ numerous best practices before, during and after surgery to decrease the risk of infection and increase positive outcomes. For more details about safety protocols at Children's Hospital of Philadelphia, see safety in surgery.

Follow-up care 

At Children's Hospital of Philadelphia, we offer ongoing support and services for patients and families at our Main Campus and throughout our CHOP Care Network. Our team is committed to partnering with parents and referring physicians to provide the most current, comprehensive and specialized care possible for your child.

Aneurysmal bone cysts can recur in 10-15 percent of patients, so it is important for your child to continue to see your child’s surgeon after treatment.

Your child will see the orthopaedic surgeon about one to two weeks after surgery, then again every three to four months for two years to monitor for possible recurrence of the growth.

During follow-up visits, X-rays and other diagnostic testing of the tumor site are recommended to closely monitor your child’s health, check the reconstruction, and make sure there is no recurrence.

If the aneurysmal bone cyst returns, surgeons will treat the recurrence with intralesional curettage, intraoperative adjuvants, and bone grafting.

In most cases, an ABC tumor will not recur more than two years after surgery.

If your child needs continued monitoring into adulthood, he can continue to see some of the same doctors who treated him. CHOP’s Bone and Soft Tissue Tumor Program works closely with Penn Medicine. For families who live farther away and need continued monitoring, our clinical professionals will help your child transition to adult care near home.

Reviewed by Kristy L. Weber, MD, FACS, Alexandre Arkader, MD

Providers Who Treat Aneurysmal Bone Cyst

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