What are the other Names for this Condition? (Also known as/Synonyms)
- ABC (Aneurysmal Bone Cyst)
What is Aneurysmal Bone Cyst? (Definition/Background Information)
- Aneurysmal Bone Cyst (ABC) is a tumor-like lesion of the bone, primarily found in children and adolescents
- This benign tumor grows rapidly and destroys any surrounding bone tissue. The most commonly affected bone is the tibia (shinbone), followed by the femur (thigh bone)
- Rarely, these tumors may occur in a non-bone location, such as in the wall of major artery, or in the soft tissues
- Conservative methods that preserve the bone stability are preferred over surgical procedures, to treat the condition
- The prognosis is usually good with early and proper treatment of ABC
There are 2 kinds of Aneurysmal Bone Cyst:
- Primary ABC: When the cause of the tumor is unknown
- Secondary ABC: When this benign tumor arises in the background of preexisting bone lesions
Who gets Aneurysmal Bone Cyst? (Age and Sex Distribution)
- Aneurysmal Bone Cyst usually develops in children or adolescents, between ages 1-20 years; the average affected age is 17 years
- There is no known gender, racial, or ethnic preference
What are the Risk Factors for Aneurysmal Bone Cyst? (Predisposing Factors)
No clear risk factors have been established for the development of Aneurysmal Bone Cyst. However, the following are thought to be associated with the condition:
- Preexisting bone lesions, such as:
- Giant cell tumor
- Fibrous dysplasia
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.
Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
What are the Causes of Aneurysmal Bone Cyst? (Etiology)
- The exact cause and mechanism of formation of Aneurysmal Bone Cyst is unknown
- Some researchers believe that the benign tumor occurs, due to some trauma or a preexisting bone lesion, which may include giant cell tumor, chondroblastoma, or fibrous dysplasia
- ABC is a relatively uncommon benign tumor that accounts for 1-6% of all primary bone tumors
What are the Signs and Symptoms of Aneurysmal Bone Cyst?
The signs and symptoms of Aneurysmal Bone Cyst include:
- Pathologic fracture in the area of the tumor
- Neurologic symptoms can occur, if ABC compresses on a nerve
- Pain in the affected bone - often the tumor is painless and is found incidentally on radiological studies, for some other health issues
- Swelling of the affected region
- Deformity of the bone
- The most prominent locations of ABC are:
- The metaphysis (zone of bone growth) of posterior vertebrae
- Flat bones
- Shaft of the long bones
- However, it is the shinbone and thigh bone, which are usually affected
How is Aneurysmal Bone Cyst Diagnosed?
The diagnostic tests may vary, based on the location of the tumor. A diagnosis of Aneurysmal Bone Cyst may involve:
- Physical examination, evaluation of the individual’s medical history
- X-ray, CT scan, or MRI scan of the affected region, to aid in obtaining a clear image of the tumor
- Tissue biopsy of the tumor - the specimen is examined under a microscope by a pathologist, to arrive at a definitive diagnosis
- Angiography of the affected site may help in determining the effectiveness of selective arterial embolization therapy
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.
What are the possible Complications of Aneurysmal Bone Cyst?
Complications due to Aneurysmal Bone Cyst could include:
- Pathological fracture of a bone, if the tumor is large
- ABC may rarely undergo malignant transformations, to form malignant osteosarcoma. These transformations occur sporadically
How is Aneurysmal Bone Cyst Treated?
The treatment of Aneurysmal Bone Cyst is undertaken as:
- Conservative treatment is the treatment of choice for ABC tumors that do not affect bone stability. Conservative methods include close observation and follow-up
- In case of large tumor causing bone stability issues, symptoms, or showing features of concern on radiological images, they can be removed by surgical Curettage of the tumor, followed by bone grafting, as needed
- Newer non-surgical techniques to treat Aneurysmal Bone Cyst include selective arterial embolization. Selective arterial embolization should not be used, if the patient has neurological symptoms or instability of the affected bone
- In some rare cases, the bone needs to be stabilized further, in order for the bone strength to increase. In such cases, bone stabilization procedures may be needed. Common bone stabilizing procedures include internal fixation and intramedullary rodding
- Other surgical methods include en bloc resection and wide excision of the affected bone
- Complete surgical excision of the tumor is curative in 75% of the individuals. In the remainder 25% of cases, Aneurysmal Bone Cyst can recur. Hence, close follow-up is needed
- In Secondary ABC, the underlying disease causing the tumor, should also be treated
- Occasionally, ABCs resolve spontaneously, without any treatment
How can Aneurysmal Bone Cyst be Prevented?
- Current medical research has not established a way of preventing Aneurysmal Bone Cyst
- Regular medical screening at periodic intervals with blood tests, scans, and physical examinations, are mandatory for those who have already endured the tumor, due to its metastasizing potential and possibility of recurrence. Often several years of active vigilance is necessary
What is the Prognosis of Aneurysmal Bone Cyst? (Outcomes/Resolutions)
The prognosis of Aneurysmal Bone Cyst is usually excellent with a correct diagnosis and treatment.
Additional and Relevant Useful Information for Aneurysmal Bone Cyst:
- Jaffe and Lichtenstein first described Aneurysmal Bone Cyst in 1942
- The differential diagnosis considered for ABC includes giant cell tumor and telangiectatic osteosarcoma
- Radiotherapy was a treatment modality in the past. However, radiotherapy is no longer used, because it can cause malignant sarcomas later on