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Aneurysmal Bone Cyst

  • Overview

    Bones naturally grow and change as your child gets older. However, throughout a long process, abnormalities can sometimes occur. An aneurysmal bone cyst (which is often abbreviated ABC) is one such abnormality treated here at Boston Children's Hospital. ABCs are blood-filled, fibrous cysts that expand the bone and can cause pain, swelling and fractures. 

    While an ABC is certainly worrisome, it may comfort you to know that these are benign cysts (non-cancerous) that don’t spread. Here are a few important things to know about an ABC: 

    • An aneurysmal bone cyst is a benign, blood-filled growth that occurs in the bone.
    • Bone cysts are not cancerous.
    • ABCs are most common during a child’s teenage years.
    • They can occur in virtually any bone in the arms, legs, trunk or skull as well as the vertebrae and knee.
    • While it’s benign, it can be quite destructive because it deforms the bone and can cause fractures.
    • ABC’s don’t spread but can be quite damaging to the bone and can come back after they are removed.
    • ABC’s can cause pain and swelling around the site of the cyst.
    • Surgery is often necessary to remove the cyst.
    • With surgery, these cysts are highly curable, although they do grow back in some cases.

    How Children’s Hospital Boston approaches aneurysmal bone cysts

    Experts in Boston Children's Hospital's Bone and Soft Tissue Program within our Orthopedic Center provide comprehensive medical and surgical care for children aneurysmal bone cysts and other bone and soft tissue disorders.

    Our multidisciplinary approach to care ensures that your child’s case receives input from experts in several fields before your care team develops a personalized treatment plan. We integrate expertise from the following specialists: 

    • pediatric orthopedic surgeons
    • pediatric experts from every medical subspecialty, such as orthopedics, pathology, physical therapy and radiology
    • pediatric nurses
    • Child Life specialists, psychologists, social workers and resource specialists who provide supportive care before, during and after your child’s treatment

    Spotlight on: Bone and Soft Tissue Tumor Program

    Learn more about our Bone and Soft Tissue Tumors Program, where we care for children with benign and malignant bone and soft tissue tumors.

    Aneurysmal bone cyst: Reviewed by Megan Anderson, MD, orthopedic surgeon
    © Children’s Hospital Boston, 2011

  • In-Depth

    We understand that you may have a lot of questions when your child is diagnosed with an aneurysmal bone cyst, such as: 

    • What exactly is it?
    • What are potential complications in my child’s case?
    • What are the treatment options?
    • What are possible side effects from treatment?
    • How will it affect my child in the long term?

    We’ve tried to provide some answers to those questions here, and when you meet with our experts, we can explain your child’s condition and treatment options fully. 

    What is an aneurysmal bone cyst?
    An aneurysmal bone cyst is a blood-filled fibrous tumor-like cyst that expands the bone. It typically occurs in teenagers and can form in virtually any bone in the arms, legs, trunk or skull. The vertebrae and knee are the most common sites.

    • While it’s benign, it can be quite destructive because it can deform and damage the bone, sometimes leading to fractures.
    • These types of cysts also tend to come back.
    • ABC’s can cause pain and swelling around the site of the cyst.
    • With surgery, these cysts are highly curable, although they do grow back in some cases.

    What are the types of aneurysmal bone cyst?
    An aneurysmal bone cyst usually falls into one of two categories: 


    • It could deform the bone it’s growing in, but remains contained in the bone. 


    • It extends beyond the bone to the nearby soft connective tissues.
    • Rarely, will these types of cysts go away on their own without treatment. 

    Both types can cause pain and swelling and, in rare cases, fractures in the involved bone. Aneurysmal bone cysts do not generally go away on their own.


    What causes an aneurysmal bone cyst?
    The cause of these cysts is unknown and controversial. Some theories include: 

    • They’re believed to grow in response to a disturbance of the blood vessels in the involved bone.
    • They may grow because of a pre-existing tumor (in half of all cases, a pre-existing tumor, such as fibrous dysplasia, nonossifying fibroma, a solitary bone cyst or osteosarcoma also exists).
    • Abnormalities in the chromosomes (karyotype) of the tumor cells have been described, but the significance of these findings is unclear. 

    In summary, at this point, there is no definitive explanation for why these cysts occur. It’s important to know that there’s nothing that you could have done (or not done) that would have prevented your child’s cyst from developing.

    Signs and symptoms

    What are the symptoms of an aneurysmal bone cyst?
    While symptoms may vary child-to-child, the most common include: 

    • pain
    • swelling
    • a mass that can be felt (sometimes)
    • mild to severe neurological problems (if the cyst is in your child's spine)
    • a fracture caused by the cyst (rarely)

    It’s important to understand that the symptoms of aneurysmal bone cyst may resemble other medical problems, some of them which are very common and easy to treat, others which could be more serious.  

    Your child may experience symptoms differently. Therefore, it is important to be evaluated by a physician to get an accurate diagnosis. Always consult your child's physician if you have concerns.

    Questions to ask your doctor

    You and your family are key players in your child’s medical care. It’s important that you share your observations and ideas with your child’s health care provider and that you understand your doctor’s recommendations.
    If your child is has been diagnosed with an aneurysmal bone cyst, you probably have a lot on your mind. So it’s often helpful to write questions down. Some of the questions you may want to ask include: 

    • What does a diagnosis of an aneurysmal bone cyst mean for my child?
    • How will my child’s symptoms be managed?
    • What kind of treatment will my child have? Is surgery needed?
    • How long will recovery take?
    • What are the possible short and long-term complications of treatment?
    • What is the long-term outlook for my child?
    • How likely is it that the bone cyst will come back?
    • What services are available to help my child and my family cope?


    Q: Will my child be OK?
    A: Children with aneurysmal bone cysts usually have very good long-term health, although the condition can recur. Patients may become frustrated, because this benign cyst can return after surgery. It may require two or three operations to eventually get rid of the cyst, but ultimately, this is a benign tumor and it does not spread. If left untreated, these cysts can cause pain, swelling and permanent damage to the bone as well as an increased risk of a fracture. 

    Q: Will my child need chemotherapy or radiation?
    A: No; a simple bone cyst is a benign condition and does not require chemotherapy or radiation. Most of the time, surgery is sufficient to cure it completely.

    Q: Where will my child be treated?
    A: If your child is treated through the Bone and Soft Tissue Tumors Program, he will receive inpatient (overnight) and outpatient (day) care at Children’s Hospital Boston. If your child needs surgery, he will see doctors in our Orthopedic Center

    Q: What services are available to help my child and my family cope?
    A: Boston Children's Hospital offers several support services to help you, your child and your family get through the challenges and stresses of dealing with your child’s illness. Learn more

    Spotlight on: Your appointment

    Questions about your visit? Check out this web page for directions, contact phone numbers and e-mail addresses and other important information.

  • Tests

    The first step in treating your child is forming an accurate and complete diagnosis. 

    How does my child’s doctor know if it's an aneurysmal bone cyst?
    Your child’s physician might order a number of different tests to determine the exact type of cyst, its size and location. These tests may include:

    • a physical exam - including checking the area where the cyst is located
    • X-rays to determine the size of the cyst and whether there is a risk of fracture
    • magnetic resonance imaging (MR or MRI), which produces detailed images of the bone where the cyst is located. This imaging scan is used to determine the internal characteristics of the cyst and the specific type of cyst.
    • computerized tomography scan (CT or CAT scan), which is used in some cases to get a clearer picture of the bone lesion
    • a biopsy or tissue sample, collected from the cyst through a needle to provide definitive information about the type of cyst 

    After we complete all necessary tests, our experts meet to review and discuss what they have learned about your child's condition. Then we will meet with you and your family to discuss the results and outline the best treatment options.

  • We know how stressful a diagnosis of an aneurysmal bone cyst can be, both for your child and for your whole family. That's why Boston Children's Hospital's physicians are focused on family-centered care: From your first visit, you'll work with a team of professionals who are committed to supporting all of your family's physical and psychosocial needs. We'll work with you to create a care plan that's best for your child.  

    Your child's physician will determine a specific course of treatment based on several factors, including: 

    • your child's age, overall health and medical history
    • the location of the cyst
    • the risk of fracture
    • whether the cyst has recurred 

    Why do the aneurysmal bone cysts need to be removed?
    Aneursymal bone cysts expand and deform the involved bone. In some cases, this can lead to damage to joints or pathological fracture (a fracture that occurs without trauma). They also cause pain and swelling around the site of the cysts and do not generally go away on their own. To prevent permanent damage to the bone, surgery is needed to cure these cysts. 

    What are the treatment options for aneurysmal bone cysts?
    Treatment options vary greatly, depending on your child's situation. Your doctor and other members of your care team will discuss the options with you in-depth. 

    There is potential for excessive blood loss during an operation to remove aneurysmal bone cysts because of the abnormal blood vessels that may be involved. As a result, surgery involves very careful planning.

    Before we decide to do surgery: 

    • A radiologist may perform a procedure called arterial embolization. This blocks the blood flow in the abnormal vessels that are involved with the cyst. This reduces the risk of excessive bleeding during surgery.
    • To determine whether your child can undergo arterial embolization without complications, your doctor may use an angiogram, a special x-ray that allows doctors to visualize the involved blood vessels.

    Traditional treatments for aneurysmal bone cysts

    Treatment for the cyst will likely involve one or more of the following surgeries performed by a pediatric orthopedic surgeon: 

    Curettage and bone grafting
    The most common treatment for an aneurysmal bone cyst, this is an operation during which the cyst is scraped out of the bone with a special instrument called a curette that has a scoop, loop or ring at its tip. The procedure itself is called curettage.

    The remaining cavity is then packed with donor bone tissue (called an allograft), bone chips taken from another bone (autograft) or other materials. 

    Extended curettage
    In some cases, Children's orthopedic surgeons perform an “extended” curettage using a special instrument (a curette) to remove additional layers of cells around the bone cyst. This is simply a more aggressive type of the procedure described above. It is done to reduce the risk that the cyst will grow back. 

    Marginal or wide excision
    This operation removes the part of the bone involving the cysts at its margins or beyond its margins (known as a wide excision). A wide excision is recommended when the cyst is located in bones considered expendable, such as the ribs or fibula. It is avoided whenever possible when the cyst occurs in a location that could compromise the bone's function. 

    This is a promising non-surgical technique for healing aneurysmal bone cysts. Instead of surgery to remove the cyst, doctors inject special chemicals into the cyst in order to promote the creation of scar tissue. This scar tissue eventually heals and hardens into bone, healing the cyst without the need for an open surgery. 

    Because it's possible that the cyst will grow back, this procedure, which surgically freezes the cyst, is sometimes used in addition to curetting and bone grafting. However, it is associated with complications such as fracture of the bone, nerve injury and others.

    Recurrence and long-term care

    How often do aneurysmal bone cysts recur?
    Aneurysmal bone cysts return about 20 percent of the time. To treat cysts that return, Children's doctors provide follow-up care for every three months for the first two years after treatment.

    Recurrent aneurysmal bone cysts are treated using the same techniques, although your child's orthopedic surgeon may opt for a more aggressive treatment to prevent further recurrence. 

    What is the recommended long-term care for children treated for aneurysmal bone cysts?Patients treated for aneurysmal bone cysts should return to Children's for frequent follow-up visits to:

    • manage disease complications
    • screen for early recurrence of the cyst

    A typical follow-up visit may include all of the following: 

    • a physical exam
    • a thorough history
    • imaging scans (such as x-rays)

    Will my child be OK in the long term?
    Children with aneurysmal bone cysts usually have very good long-term health, although the condition can recur. Patients may become frustrated, because this benign cyst can return after surgery.

    It may require two or three operations to eventually get rid of the cyst, but ultimately, this is a benign tumor and it does not spread. If left untreated, these cysts can cause pain, swelling and permanent damage to the bone as well as an increased risk of pathological fracture. 

    Spotlight on: Orthopedics at Children's
    Learn more about our Orthopedic Center and world-renowned team of orthopedic surgeons.

    Coping and support

    In addition to providing exceptional medical care, Children's strives to also meet all of your family's emotional and quality-of-life needs.

    We know that unfamiliar places, especially hospitals, often create anxiety and fear for a child. We also know this isn't an easy time or task for parents, who have their own fears and concerns about the situation. Our family support services will help address many of your needs and concerns.

    Read about our resources and support services. 

    Did you know?

    You can keep family and friends up to date during your child's treatment by creating a free Children's Carepage.

  • Research & Innovation

    At Boston Children's Hospital, our care is informed by our research. We have a long history of research and innovation in pediatric orthopedics. Key highlights include:

    • Our interventional radiologists offer an advanced procedure called sclerotherapy to heal aneurysmal bone cysts without the need for open surgery.
    • Our basic science researchers are investigating the genetic causes of aneurysmal bone cysts.
    • Our pathologists were the first to describe the genetic abnormalities in these cysts.

    Children's is a world leader in opening new avenues of "translational research," bringing laboratory advances to the bedside and doctor's office as quickly as possible. All of our senior medical staff members of the Bone and Soft Tissue Tumor Program participate in clinical research activities. Our program director, Carlos Rodriguez-Galindo, MD, is also the co-director of our new Clinical and Translational Investigation Program, which aims to dramatically improve translational research in pediatric hematology and oncology. 

    In addition to a variety of clinical trials, Children’s also conducts extensive laboratory research to identify new treatments and improve therapies for benign and malignant bone and soft tissue tumors. 

    Learn more about our current research. 

    Spotlight on: Clinical trials

    Find out more about the innovative clinical trials available at the Dana-Farber/Children’s Hospital Cancer Center.

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