Aneurysmal Bone Cyst (ABC)

Key Points:

  • Benign lesion of bone
  • Approximately 30% arise secondary to different primary tumors
  • Differential diagnoses benign lesions: giant cell tumor, unicameral bone cysts, chondroblastoma, fibrous dysplasia, non-ossifying fibroma, chrondromyxoid fibroma, osteoblastoma
  • Differential diagnosis malignant lesions: telangiectatic osteosarcoma

Description:

Aneurysmal bone cyst (ABC) is a benign and non-neoplastic reactive bone lesion with multiple blood-filled cavities. Histologically, it is a cavernous vascular tumor that can range from a few millimeters to 1-2 cm in diameter with intralesional communicating cavitations. The cavity spaces are separated by fibrous septa made of spindle cells, inflammatory cells, and giant cells.

Epidemiology:

Primary ABCs occurs in 0.14 to 0.32 per 100,000 individuals. 75% of patients with this condition are older than 20 years. It occurs in males more often than females. Common sites of presentation include the calcaneus, femur, tibia, fibula, humerus, skull, and posterior elements of spine.

Clinical Findings:

Patients with this condition often present with pain and soft tissue swelling secondary to a pathological fracture.

Imaging Studies:

In an initial evaluation, radiographs show a radiolucent cystic lesion in the metaphyseal portion of bone. This lesion expands the surrounding cortical bone. The lesion is most often eccentric but can be central or subperiosteal.
 
CT scans can be utilized to better define the bony limits of the identified lesion. MRI with contrast will reveal internal septations with fluid-fluid levels. This finding on MRI could also be suggestive of telangiectatic osteosarcoma, giant cell tumor, secondary ABC, or fracture through a simple cyst.

Etiology:

There are multiple theories for the etiology of a primary ABC including a response to traumatic local hemorrhage, a reactive lesion due to altered intraosseous blood flow, and a true neoplasm secondary to gene rearrangements (Rapp, 2012).
 
Approximately 30% of ABCs arise secondary to different primary tumors including chondroblastoma, osteoblastoma, giant cell tumor, and fibrous dysplasia.

Treatment:

After confirming the diagnosis histopathologically, treatment is pursued. Curettage and bone grafting with or without adjuvant therapy is the accepted method of treatment. Adjuvant therapy treats microscopic disease contamination. Curettage is done through either small fenestration, cortical window or complete saucerization. Cryotherapy and sclerotherapy are methods of adjuvant treatment used in conjunction to curettage to decrease recurrence rate.
 
Radionuclide ablation and arterial embolization are other potential methods to treat ABCs. However, these methods are not first line treatment. En bloc resection of ABCs is associated with the lowest rate of recurrence but is only indicated in expendable bone locations (eg, fibular, clavicle) and where performing this can be achieved without affecting cosmesis or function.
 

Complications:

Recurrence
Younger age and open physes are known risk factors for ABC recurrence. Histologically, an ABC with a higher proportion of cellular tissue relative to the amount of osteoid and fibrillary content is a prognostic indicator of recurrence (Docquier, 2010). In addition, the presence of higher mitotic indices is a risk factor for an increased recurrence rate (Reuiter et al, 1977).
 
Malignant Transformation
Malignant transformation is rare and can occur with and without the use of adjuvants during primary treatment. Malignant transformation from ABC to fibroblastic osteosarcoma and telangiectatic osteosarcoma has been reported.

References:

  1. Bas¸arir K, Pis¸kin A, Güçlü B, Yildiz Y, Sag˘lik Y: Aneurysmal bone cyst recurrence in children: A review of 56 patients. J Pediatr Orthop 2007;27(8): 938-943.
  2. Brindley GW, Greene JF Jr, Frankel LS: Case reports: Malignant transformation of aneurysmal bone cysts. Clin Orthop Relat Res 2005;438:282-287.
  3. Bush CH, Adler Z, Drane WE, Tamurian R, Scarborough MT, Gibbs CP: Percutaneous radionuclide ablation of axial aneurysmal bone cysts. AJR Am J Roentgenol 2010;194(1):W84-90.
  4. Cottalorda J, Bourelle S: Current treatments of primary aneurysmal bone cysts. J Pediatr Orthop B 2006;15(3):155-167.
  5. de Silva MV, Raby N, Reid R: Fibromyxoid areas and immature osteoid are associated with recurrence of primary aneurysmal bone cysts. Histopathology 2003;43(2):180-188.
  6. Docquier PL, Delloye C, Galant C: Histology can be predictive of the clinical course of a primary aneurysmal bone cyst. Arch Orthop Trauma Surg 2010;130(4):481-487.
  7. Dormans JP, Hanna BG, Johnston DR, Khurana JS: Surgical treatment and recurrence rate of aneurysmal bone cysts in children. Clin Orthop Relat Res 2004; (421):205-211.
  8. Enneking WF: A system of staging musculoskeletal neoplasms. Clin Orthop Relat Res 1986;(204):9-24.
  9. Jaffe HL, Lichtenstein L: Solitary unicameral bone cyst: With emphasis on the roentgen picture, the pathologic appearance and the pathogenesis. Arch Surg 1942;44:1004-1025.
  10. Peeters SP, Van der Geest IC, de Rooy JW, Veth RP, Schreuder HW: Aneurysmal bone cyst: The role of cryosurgery as local adjuvant treatment. J Surg Oncol 2009;100(8):719-724.
  11. Rapp TB, Ward JP, Alaia MJ: Aneurysmal Bone Cyst. J Am Acad Orthop Surg 2012; 20: 233-241.
  12. Ruiter DJ, van Rijssel TG, van der Velde EA: Aneurysmal bone cysts: A clinicopathological study of 105 cases. Cancer 1977;39(5):2231-2239.
  13. Varshney MK, Rastogi S, Khan SA, Trikha V: Is sclerotherapy better than intralesional excision for treating aneurysmal bone cysts? Clin Orthop Relat Res 2010;468(6):1649-1659.

Top Contributors:

Dr. Janay Mckie