Aneurysmal Bone Cyst Symptoms & Causes

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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

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