Aneurysmal Bone Cysts: Causes, Treatment, Outlook, and More

Medically Reviewed By Daniel Wiznia, MD

Aneurysmal bone cysts are fluid-filled growths that develop on the bone. While they are mostly noncancerous, they can grow quickly and cause complications. However, surgery can sometimes treat the condition. This article explains the symptoms, causes, and diagnosis of aneurysmal bone cysts. It also discusses treatment and outlook for the condition and answers some frequently asked questions.


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Aneurysmal bone cysts are rare, rapidly growing lesions that develop on the bone. They can be filled with blood and other fluids. While mostly noncancerous Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source , they can cause damage to the surrounding areas of bone and tissue.

Aneurysmal bone cysts commonly affect children and people under the age of 20. However, they can develop at any age.

Symptoms of aneurysmal bone cysts can include:

  • pain, which may develop over weeks to months
  • swelling or inflammation
  • a lump, which you may be able to feel or see
  • bone fractures
  • impaired function of affected areas

You may also experience additional symptoms depending on where the cyst develops. For example, aneurysmal bone cysts that develop on the spine may affect the nerves. This can cause neurological symptoms such as numbness or muscle weakness.

Most aneurysmal bone cysts occur in parts of the long bones. They affect areas known as the growth plates or proximal joints. Examples of long bones include the femur, located in the upper leg, and the humerus, located in the arm. However, they can develop in any bone, such as the spine, pelvis, and head bones.


Staging aneurysmal bone cysts can help doctors monitor growth and determine how far the condition has progressed. Stages can include:

  • Stage 1: This is the latent or inactive stage. At this stage, bone cysts are usually found Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source by accident during scans for other conditions. They do not cause any symptoms.
  • Stage 2: This is the active stage, during which the cysts are growing. They cause symptoms, but you may be able to feel them. Discovery of cysts at this stage may be due to noticeable symptoms.
  • Stage 3: This is known as the aggressive stage. In this stage, cysts cause significant symptoms and discomfort. They may also cause inflammation and a visible difference to the affected area.

When to see a doctor

Contact your doctor promptly for any mild symptoms that do not improve within a few days. This can also include symptoms that change, persist, or improve and then worsen again.

Aneurysmal bone cysts can sometimes cause fractures, which require immediate medical treatment. Call 911 or seek emergency medical care for symptoms such as:

  • sudden or intense pain
  • visible lumps or misshapen bone
  • swelling, bruising, or bleeding
  • difficulty moving the affected area
  • broken skin with visible bone


Clinicians are unsure what causes aneurysmal bone cysts.

Researchers currently believe they may occur Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source due to structural differences in the blood vessels of the bones. This may cause increased pressure in the veins and expansion of the bone, affecting bone growth and structure. However, researchers are still unsure what causes these structural differences in the first place.

Additional theories suggest that aneurysmal bone cysts may grow at the site of a previous injury.

Less commonly, aneurysmal bone cysts may occur secondary to other bone lesions. This means that they can occur due to the effects of another underlying condition. Conditions that may lead to aneurysmal bone cysts include cancerous and noncancerous bone tumors.

Learn more about bone cancer, including its symptoms and treatment.


To make a diagnosis, your doctor will review your symptoms and perform a physical exam. They may also ask about your medical history.

Your doctor may then order tests to confirm a diagnosis. These can include:

During diagnosis, your doctor will try to rule out other conditions that may resemble aneurysmal bone cysts. They may also try to rule out any bone cancers that may be contributing to bone cysts.


Treatment for aneurysmal bone cysts primarily focuses on surgeries to remove them. This can prevent fractures and other complications. Surgeries for aneurysmal bone cysts can include:

  • Intralesional curettage: This involves removing the cyst and strengthening the area with bone grafts or other material.
  • Intralesional excision: This can be similar to intralesional curettage. However, it can make a broader opening in the lesion. This allows the use of additional therapies at the site, such as cryotherapy.
  • En bloc excision: This surgery also removes the lesion from the bone. However, it can remove more bone tissue than other procedures.

Your doctor may also recommend selective arterial embolization (SAE) before surgery or as an alternative to surgery. This blocks the blood supply to the cysts to help stop their growth. However, as much as 40% Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source of people treated with SAE may require a repeat SAE treatment.

Researchers are also investigating therapies that use antibodies to help treat aneurysmal bone cysts. Although, they are not yet part of standard treatment plans.


While aneurysmal bone cysts are noncancerous, they can grow rapidly and can cause complications.

As they commonly occur in children, aneurysmal bone cysts may impact bone growth, such as affecting limb length.

Other complications can include:

  • fractures
  • damage to the affected bone and surrounding area
  • impaired use of the affected area
  • bone weakening
  • impaired quality of life
  • rarely Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source , the development of bone cancer, particularly after radiotherapy treatment
  • surgical complications, such as:
    • infection
    • bone damage or bone loss
    • bleeding

Complications and outlook can vary per person. For example, someone with aneurysmal bone cysts as a secondary effect of cancer may experience additional complications.

For some people, effective surgical removal of aneurysmal bone cysts can cure Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source the condition.

However, aneurysmal bone cysts can reoccur spontaneously in around 19% of people with the condition. Because of this, your doctor may recommend regularly monitoring your bone health for a few years after initial treatment.

Talk with your doctor about outlook and treatments for your specific condition.


Daniel Wiznia, M.D., has reviewed the following frequently asked questions.

How serious is an aneurysmal bone cyst?

The severity of an aneurysmal bone cyst can vary per person. Some people may experience complications such as impaired bone growth, fractures, or bone loss.

Aneurysmal bone cysts are not cancerous and can be effectively treated with surgery. However, they can still be serious if you experience complications or don’t receive effective medical care.

Are bone cysts ever cancerous?

Bone cysts are not cancerous. However, some clinicians suggest that, in rare cases, they occur as a complication of preexisting bone cancer.

In some cases, aneurysmal bone cysts later became cancerous, although this is also rare.

What does an aneurysmal bone cyst feel like?

How an aneurysmal bone cyst feels can vary per person. However, you may notice a visible lump that you can also feel. You may also have an inability to move the affected area as normal.

You may experience bone or joint pain that develops slowly over weeks or months.


Aneurysmal bone cysts are rapidly growing fluid-filled lesions that can develop on the bone. They can cause symptoms of pain, lumps that you can see or feel, and inflammation.

Clinicians are not yet sure why aneurysmal bone cysts develop. However, they may occur due to blood vessel changes in the bone. They may also develop as a secondary effect of bone cancer.

Treatment with surgery can completely remove the cysts. It can also reduce the risk of complications, such as fractures and impaired bone growth.

Contact your doctor promptly if you experience any symptoms of aneurysmal bone cysts.

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Medical Reviewer: Daniel Wiznia, MD
Last Review Date: 2023 Feb 23
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