Aneurysmal Bone Cyst: Symptoms, Causes & Treatment Options

What is an Aneurysmal Bone Cyst?

An aneurysmal bone cyst (ABC) is a rare, benign bone lesion characterised by multiple blood-filled spaces separated by connective tissue septa. Despite its name, it is neither a true aneurysm nor a simple cyst; rather, it represents a locally destructive, expansile bone lesion that can expand and weaken bones from within. According to an article published by StatPearls in 2023, aneurysmal bone cysts are rare, making up only 1–6% of primary bone tumours, but they occur predominantly in children and adolescents (occurring in approximately 80% of cases under 20 years of age) and, despite being non-malignant, can grow aggressively enough to weaken bone and cause pathological fractures.

These cysts most commonly develop in the long bones of the arms and legs, as well as in the spine and pelvis, with a slight female predominance. As the lesion grows, it appears as an expansive, balloon-like cavity that thins the bone’s cortical layer, causing progressive deformity, pain, and an increased risk of pathological fracture. This aggressive, expansile nature distinguishes aneurysmal bone cysts from many other bone diseases and makes early diagnosis crucial to prevent long-term complications and disability.

Symptoms of an Aneurysmal Bone Cyst

The symptoms of aneurysmal bone cyst typically develop gradually but can become increasingly troublesome:

• Localized bone pain that gradually worsens over time, often the earliest symptom.
• Swelling or a visible lump over the affected bone area.
• Warmth and tenderness around the cyst location.
• Limited range of motion if the cyst affects joints.
• Limping or difficulty walking when the lower limbs are involved.
• Sudden severe pain from pathological fractures through weakened bone.
• Visible deformity as the bone expands outward.
• Neurological symptoms such as numbness or weakness may occur if the spinal aneurysmal bone cyst compresses nerves.

Causes of Aneurysmal Bone Cyst

The exact cause of aneurysmal bone cysts is not fully understood. Many primary ABCs arise from rearrangements involving the USP6 gene, leading to abnormal bone resorption and cyst formation. Some ABCs occur secondary to other bone diseases such as osteomalacia, bone tumours, or trauma. Increased pressure within the bone causes expansion, blood pooling, and destruction of bone tissue, which explains their rapid growth.

How is an Aneurysmal Bone Cyst Diagnosed?

Diagnosing aneurysmal bone cyst involves several systematic steps:

1. Clinical evaluation: Assessment of pain, swelling, movement restriction, and history of trauma.
2. Radiologic imaging (X-ray, CT, and MRI): Demonstrates the classic ‘soap-bubble’ expansile lesion with multiple fluid–fluid levels.
3. Bone and Joint Tests: Helps rule out underlying bone diseases, metabolic disorders, or osteomalacia.
4. Biopsy: Confirms the diagnosis and differentiates ABC from malignant bone tumors or metastatic lesions.
5. Bone Profile or Osteomon Profile: Measures calcium, phosphate, and bone turnover markers to evaluate overall bone health.

Diseases Related to the Aneurysmal Bone Cyst

Several conditions can be associated with or mistaken for aneurysmal bone cyst:

• Giant cell tumor of bone – a benign but locally aggressive tumor.
• Chondroblastoma – a cartilage-forming tumour often in bone ends.
• Osteoblastoma – a benign bone-forming tumour often affecting the spine.
• Fibrous dysplasia – benign fibro-osseous bone condition.
• Unicameral bone cyst – single-chamber fluid-filled cyst.
• Telangiectatic osteosarcoma – a rare malignant bone tumor that can mimic ABC on imaging but requires different management.

Diagnostic Tests to Identify an Aneurysmal Bone Cyst

Various diagnostic tests help confirm aneurysmal bone cyst diagnosis:

• Imaging: X-ray, CT, and MRI to identify the classic expansile, “soap-bubble” cyst and fluid–fluid levels.
• Bone health tests: Bone health panels such as Calcium Profile, Vitamin D Plus Profile, and Osteomon Profile to assess overall bone strength and metabolism.
• Bone turnover markers: Osteocalcin and P1NP (Total) to check how actively bone is being formed and broken down.
• Comprehensive bone status: Bone Screening Profile or Bone Resorption/Formation Marker Profiles to rule out other metabolic bone diseases.
• Tissue confirmation: Bone Biopsy with Histopathological Examination to confirm ABC and exclude bone malignancy or marrow disorders.

Treatment Options for Aneurysmal Bone Cyst

Treatment approaches for aneurysmal bone cyst vary based on location, size, and patient factors:

• Surgical curettage and bone grafting - standard treatment involving cyst removal and cavity filling.
• En bloc resection - complete lesion removal for aggressive or recurrent cases.
• Selective arterial embolisation - blocking the blood supply to reduce cyst activity.
• Sclerotherapy - injection of sclerosing agents (such as polidocanol or doxycycline) to induce cyst closure.
• Percutaneous injection techniques - minimally invasive approaches for suitable cases.

Surgery for Aneurysmal Bone Cyst

Surgical treatment remains the standard of care for most aneurysmal bone cysts. The procedure typically involves thorough curettage (scraping out) of the cyst contents, followed by bone grafting to fill the resulting cavity. For spinal aneurysmal bone cysts, surgery may require meticulous decompression to protect neural structures. Success rates are high, though recurrence occurs in approximately 10–20% of cases, particularly in younger patients.

Non-surgical Treatment for Aneurysmal Bone Cyst

Non-surgical options may be appropriate for certain patients:

• Selective arterial embolization using coils or particles to reduce blood flow.
• Percutaneous sclerotherapy with agents like polidocanol or ethanol.
• Calcitonin or bisphosphonate therapy to reduce bone resorption.
• Observation with monitoring for small, asymptomatic lesions.
• Activity modification to prevent pathological fractures.

Potential Complications of Aneurysmal Bone Cyst

Without proper treatment, an aneurysmal bone cyst can lead to several complications:

• Pathological fractures occur through weakened bone structure.
• Progressive bone deformity affects function and appearance.
• Neurological complications from spinal cord or nerve compression.
• Growth disturbances may occur in children if the growth plates are affected.
• Joint dysfunction occurs when cysts extend into joint spaces.
• Recurrence after treatment requires additional interventions.
• Infection risks following surgical procedures.

Prognosis for Aneurysmal Bone Cyst

Most aneurysmal bone cysts respond well to treatment, especially when diagnosed early. Surgery and minimally invasive options offer excellent recovery, and children often regain full function. However, recurrence can occur, especially in cysts located in the spine or pelvis. Long-term monitoring, periodic imaging, and bone and joint tests help track bone healing and prevent complications.

Conclusion

Aneurysmal bone cysts are treatable, especially when diagnosed early with the right imaging and bone health evaluations. Most patients recover well with timely surgical or minimally invasive treatment.

Metropolis Healthcare supports this journey with 4,000+ tests, specialized bone and tumor panels, full-body checkups, and reliable home sample collection across 10,000+ touchpoints. With quick turnaround, accurate reports, and easy booking via website, app, WhatsApp, or call, patients receive seamless, dependable diagnostic support throughout their care.

FAQs

What is an aneurysmal bone cyst?

An aneurysmal bone cyst is a benign, blood-filled bone lesion that grows rapidly and weakens bone. It commonly affects children and young adults and requires proper imaging and biopsy for confirmation.

How is an aneurysmal bone cyst treated?

Treatment includes curettage, bone grafting, sclerotherapy, embolisation, or complete surgical excision. The choice depends on the cyst's size, location, and symptoms.

Can an aneurysmal bone cyst return?

Yes. Recurrence rates range from 10–30%, especially in younger patients or cysts in complex locations like the spine. Regular follow-up imaging is important.

Is surgery required for an aneurysmal bone cyst?

Not always. Small or accessible cysts may respond to minimally invasive treatments like sclerotherapy or embolisation. Surgery is recommended for large, symptomatic, or recurrent ABCs.