Aneurysmal Bone Cyst

What is an aneurysmal bone cyst?

Aneurysmal bone cysts are benign (noncancerous) tumor-like lesions found in bones. Though they can grow rapidly, they don't spread to other locations in the body.

Aneurysmal bone cysts can occur in any bone. The most common locations are near the ends of the long bones of the arms and legs. Other common locations include the bones of the spine and pelvis.

Aneurysmal bone cysts grow as blood-filled tumors. They can become large, causing pain and swelling and weakening the bone until it fractures.

Surgery is an effective treatment, although cysts return in about 1 in 5 people.

What are the types of aneurysmal bone cysts?

Aneurysmal bone cysts can be classified by whether they develop alone (primary) or along with another type of bone tumor (secondary).

About 1 in 3 aneurysmal bone cysts are secondary cysts caused by:

• Benign bone tumors, such as fibrous dysplasia, giant cell tumors or osteoblastoma.
• Bone cancers, such as chondrosarcomas and osteosarcomas.

Are aneurysmal bone cysts similar to other bone tumors?

In imaging tests, aneurysmal bone cysts may appear similar to other noncancerous and cancerous bone tumors. Providers use biopsy and other diagnostic procedures to get an accurate diagnosis.

Aneurysmal bone cysts may look like:

• Giant cell tumor: These tumors occur close to the joints in the long bones of the arms and legs. They usually do not occur in children, most often affecting adults ages 20 to 40.
• Simple bone cysts (unicameral bone cysts): Like aneurysmal bone cysts, these are fluid-filled tumor-like lesions, but they don’t grow beyond the original size of the bone.
• Telangiectatic osteosarcoma: This fast-growing type of cancerous bone cyst can spread to other areas of the body. It looks very similar to an aneurysmal bone cyst. A biopsy is the best way to find out if it’s an aneurysmal bone cyst or telangiectatic osteosarcoma.

How common are aneurysmal bone cysts?

Aneurysmal bone cysts are rare. They make up just a small percentage of all bone tumors, which are rare themselves. Most aneurysmal bone cysts occur in young people under the age of 20.

What causes aneurysmal bone cysts?

Healthcare providers are not sure what causes aneurysmal bone cysts. They seem to be due to a defect in the blood vessels in the bone.

In some people with primary aneurysmal bone cysts, a genetic mutation — a change in the cell’s DNA — may also be involved. Researchers have identified a genetic mutation that triggers tumor growth.

What are the symptoms of an aneurysmal bone cyst?

Symptoms of an aneurysmal bone cyst may include:

• Pain that develops slowly.
• Swelling.
• Lump.
• Sudden pain, if the bone fractures.

If the cyst is on the spine, you or your child may have neurological symptoms such as numbness, tingling, muscle weakness or paralysis. The location of these symptoms depends on where in the spine the lesion is located.

How is an aneurysmal bone cyst diagnosed?

You or your child’s healthcare provider will:

• Ask about symptoms.
• Perform a physical exam, checking overall health and assessing the lump and the area around it.
• Order additional testing if they suspect a bone tumor.

What tests are used to diagnose an aneurysmal bone cyst?

To diagnose an aneurysmal bone cyst, healthcare providers may use:

• Imaging tests: These tests help your provider see the structure of the tumor and include X-rays, MRI scans and CT scans.
• Bone scan: This type of nuclear imaging test can detect bone diseases, including cancer. The provider inserts a small amount of radioactive tracer into a vein. Cancer cells absorb more of the tracer than other cells and show up as bright areas on the scan.
• Biopsy: During a biopsy, a healthcare provider inserts a needle into the lesion to collect a small tissue sample. A pathologist, an expert in diseases, examines the tissue under a microscope to look for abnormalities. The pathology of an aneurysmal bone cyst can help providers determine the correct diagnosis, which will guide treatment.

What surgery treats aneurysmal bone cysts?

If you or your child receives an aneurysmal bone cyst diagnosis, your healthcare provider will refer you to an orthopaedic oncologist. This specialist has training in bone cancer.

People with an aneurysmal bone cyst usually need surgery. In the past, surgeons removed the entire cyst (en bloc excision), including part of the bone. This type of treatment often led to shortened limbs, muscle weakness or decreased range of motion.

Today, providers typically use en bloc excision only for recurring aneurysmal bone cysts that do not respond to other treatments. Current surgical treatment uses curettage, a less aggressive technique that has good results.

What happens during curettage for aneurysmal bone cysts?

During curettage, the surgeon opens the tumor and scrapes out its contents and lining. Once the surgeon has scraped out the tumor, a tumor cavity remains — a hollow area where the tumor was.

To clean out the tumor cavity and destroy any remaining tumor cells, the surgeon may use one or more additional treatments, including:

• High-speed burr, a rotary tool that removes the inner layer of the cavity.
• Argon beam coagulation, an electrical current produced by a beam of argon gas.
• Phenol, a strong chemical.
• Cryotherapy, freezing temperatures produced by liquid nitrogen.
• Cement, a synthetic material that stabilizes the cavity and kills cells with the heat it gives off as it hardens.

Afterward, the surgeon may fill the cavity with a bone graft to help you heal faster. The bone graft is a piece of bone taken from another part of your body or from a donated bone.

Are there less invasive treatment options for aneurysmal bone cysts?

Healthcare providers have several minimally invasive or noninvasive options for treating aneurysmal bone cysts. Providers use these procedures less frequently than surgery. But these treatments are useful if surgery is not an option due to tumor location or another factor.

Other treatments for aneurysmal bone cysts include:

• Arterial embolization: This treatment involves blocking the blood vessels that feed the tumor, starving it of needed nutrients and oxygen.
• Curopsy: This procedure is similar to a biopsy but uses a larger instrument to collect a sample of the tumor and its lining. Curopsy causes a disturbance that can lead to natural healing of the tumor.
• Doxycycline treatment: Doxycycline is an antibiotic that has anti-cancer properties. Providers inject a series of doxycycline injections directly into the tumor.
• Medication therapy: Medications, such as bisphosphonates and denosumab, can reduce tumor size and tumor-related pain. These new technologies hold promise for noninvasive treatments that minimize the side effects of surgery.
• Radiation therapy: During radiation therapy, providers focus high-energy radiation beams on the tumor to destroy tumor cells.
• Sclerotherapy: During sclerotherapy, providers inject a solution into the veins and arteries inside the tumor. Sclerotherapy is frequently used as a treatment for varicose veins. The solution thickens (coagulates) blood and destroys the veins and arteries.

Will I need follow-up care after treatment for an aneurysmal bone cyst?

Follow-up care depends on the location of the tumor and the type of treatment you or your child receives. Physical or occupational therapy can help you return to your regular activities as soon as possible. After treatment, your provider will monitor you to watch for recurrent cysts (cysts that may return).

How can I prevent an aneurysmal bone cyst?

Since providers don’t know the exact cause of aneurysmal bone cysts, there’s no way to prevent them.

What is the prognosis for people with an aneurysmal bone cyst?

Aneurysmal bone cysts are highly treatable, though they come back in about 1 in 5 people. Recurrence is most common within the first year after treatment. Your provider will monitor you closely for at least five years after surgery.

What are the complications of aneurysmal bone cysts?

Lesions that occur near the growth plates could interfere with bone growth, resulting in a bone that is too short or deformed. Your healthcare provider will talk to you about treatment options if this happens to you

How can I live best after aneurysmal bone cyst treatment?

Follow-up care for you or your child may involve routine check-ups and physical and occupational therapy to help regain function and mobility. Follow the provider’s care plan and attend follow-up appointments, so you can get back to your active life.

When should I contact my healthcare provider?

Early detection and treatment are best. If you notice a lump or swelling near your bone or experience pain, call your healthcare provider.