An aneurysmal bone cyst is a non-cancerous cavity formed in the bone filled with fluids like blood. Read the article to learn about the causes, pathology, and how to manage them.
An aneurysmal bone cyst (ABC) is a benign destructive bone tumor that occurs most commonly in children or teenagers. It forms a cavity in the bone filled with fluids that tend to grow or enlarge. These cavities can weaken the bone, cause pain, swelling, and make it more prone to fracture. They are usually non-cancerous. About 70 percent of the aneurysmal bone cyst are the primary lesions in patients with no other diseases. But 30 percent of them appear in patients secondary to other bone lesions like hemangiomas, giant cell tumors, fibrous dysplasia, osteoblastoma, etc.
The cause of an aneurysmal bone cyst is unknown, but it may be due to the involved bone's blood vessels' disturbances. In another study, it was said that the aneurysmal bone cyst is due to the abnormalities in the chromosomes of the tumor cells, but these findings are unclear. It is not hereditary because none of the patient's family members are diagnosed with an aneurysmal bone cyst. The oncogenes are the tumor-causing cells that are activated by chromosomal translocation. These oncogenes can trigger destructive tumor tissue development, made up of giant cell osteoclast and vascular spaces. The oncogenes also trigger the matrix metalloproteinase, a protein that destroys and attacks the structural matrix of the bone and vascular endothelial growth factor in the body, which recruits more blood supply for the destructive tumor to make it grow rapidly.
The symptoms of an aneurysmal bone cyst might vary from child to child. The patient will realize that they have an aneurysmal bone cyst only when they have pain in the affected bone. In other patients, the involved bone will be fragile and thin, and the aneurysmal bone cyst will be discovered only when the bone fractures due to minimal trauma. The most common symptoms are:
Fracture of the involved bone due to the cyst.
Each child may get different symptoms, so it is essential to consult with a physician to diagnose appropriately.
The aneurysmal bone cyst usually occurs in children and young adults, with about 80 percent of the cases diagnosed in patients less than 20 years of age.
Aneurysmal bone cyst consists of hollow spaces filled with blood and separated by the connective tissues and contains giant osteoclast cells and osteoid tissues. It is usually seen in the tubular bones in the feet, hands, and craniofacial bones. When it is seen in the long appendicular bones, it is known as a solid aneurysmal bone cyst.
The differential diagnosis of an aneurysmal bone cyst may include:
Giant cell tumor of bone.
The diagnoses of an aneurysmal bone cyst may include:
X-rays are done to determine the actual size of the cyst and any risk of fracture to the bone.
MRI (magnetic resonance imaging), when done, can reveal the images of the cysts where it is located and the characteristics of the cysts.
CT (computerized tomography) is used to get a clear image of the bone lesion.
The biopsy is done by collecting a tissue sample from the cyst to determine the type of cyst.
The treatment is planned based on several factors that include:
Age of the child.
The overall health of the child.
The location of the cyst.
Recurrence of the cyst.
The risk of fracture of the bone.
The aneurysmal bone cyst can expand and alter the involved bone, and it may lead to pathological fracture and damage of the joints involved. They may cause pain and swelling and do not go away on their own. Surgery is required to avoid permanent damage to the bone. And before surgery, the surgeon may block the abnormal blood vessels present in the involved cysts through arterial embolization, which can reduce the excessive blood flow during the surgery. To know whether your child can undergo arterial embolization, your doctor may use an angiogram, a special x-ray used to visualize the blood vessel. The treatment may involve one or more of the following, done by a pediatric orthopedic surgeon.
1. Extended Curettage:
After the surgery, the additional layers of bone are removed with a special instrument in this procedure. It is the most aggressive type of procedure, but it is used to avoid further growth of cysts.
2. Curettage And Bone Grafting:
This is a surgery in which the cysts are scraped from the bone with a special instrument, and the remaining cavity is filled with the bone tissue from the donor (allograft) or from the bone chips of another bone (autograft).
3. Marginal Or Wide Excision:
This surgery involves removing part of the bone where the cyst is present, at its margin or beyond its margin, called wide excision. It is often performed in bones such as ribs and fibula. This procedure is avoided as much as possible because it could compromise the bone's function.
Since the cysts can recur, in this procedure, the cysts are surgically frozen. It is sometimes done in addition to curettage and bone grafting, but it has complications like bone fracture, nerve injury, etc.
This is a non-surgical technique that is very helpful in healing the cyst. In this, the surgeon may inject a chemical inside the cyst to create scar tissue. This scar tissue may heal and harden inside the bone itself by avoiding open surgical methods.
The aneurysmal bone cyst can recur about 20% of the time; therefore, the children's doctor may call them for follow-up checkups for the first two years after the surgery to avoid recurrence. The recurrent aneurysmal bone cyst is treated with the same treatment option, but a more aggressive technique is avoided to prevent further recurrence.
For more information, consult a doctor online at iCliniq.com.
Most bone cysts are not serious, and they regress on their own or get better with time. They are slow-growing and do not cause symptoms. A majority of times, bone cysts are detected in radiographs taken for other problems or purposes.
Bone cysts are not cancerous. But aneurysmal bone cyst, a type of bone cyst, is locally invasive, meaning, if left untreated, they might destroy the involved bone leading to thinning of the bone, fragility, and pathologic fractures.
Bone cysts do not spread to other parts of the body. They are localized cysts of bones. However, untreated relatively serious aneurysmal bone cysts might expand within the area of occurrence, destroying the bone and structures surrounding it.
Different cysts have different rates of growth. In the case of bone cysts, these are slow-growing cysts. But aneurysmal bone cysts are relatively fast-growing variants.
Most bone cysts do not cause symptoms, but larger bone cysts cause pain and swelling at the site of involvement. Sometimes the affected body part might be bent.
Bone cysts have a preponderance of children and adolescents or young adults. It occurs mostly in the second decade of life. Otherwise, it is rare for someone to get bone cysts after 20 or 25 years of age.
Aneurysmal bone cysts cause pain in the involved bone. Sometimes there is thinning of the bone due to the expansion of the cyst, which leads to fracture of the bone even with minute trauma.
Aneurysmal bone cysts are benign cysts. They are locally invasive reactive bony lesions. The cysts are blood-filled.
Among the bone cysts, aneurysmal bone cysts have a high recurrence rate after surgical treatment. It ranges from 10 to 60 percent.
Aneurysmal bone cysts are rare bone cysts affecting less than one person per one lakh population per year.
Approximately 15 to 20 percent of aneurysmal bone cysts affect the spine, especially the lumbar region and posterior components of the vertebral column. The radiological findings include:
- Ballooning of the posterior vertebral components with thinning of the bony rim.
- Fracture of the vertebral bodies.
- Multiloculated and multiseptate lytic lesions.
- Fluid-filled levels.
An aneurysmal bone cyst is a noncancerous aggressive cystic lesion affecting the bone while hemangioma is a noncancerous tumor made of blood vessels that can affect skin, muscle, bone, or other organs.
Not all bone cysts are removed for therapeutic reasons. Most bone cysts regress on their own with time. But bone cysts getting bigger and causing pain sometimes need to be removed or scraped out. They can also be treated by draining the fluid-filled bone cavity and injecting medicines into it.
A tumor forms as a result of a build-up of abnormal cells due to continuous and rapid cell division and multiplication, while a cyst is a sac-like growth that encloses fluid, gas, or other substances. In most cases, cysts are benign, but tumors can either be benign or malignant.
Last reviewed at:
24 Jun 2022 - 4 min read
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