What are aneurysmal bone cysts?

Updated: Nov 01, 2018
  • Author: Andrew A Sama, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Answer

Aneurysmal bone cysts (ABCs) typically affect young patients, with 80% occurring in people younger than 20 years. The spine is involved 12-30% of the time. The thoracic spine is affected most commonly, followed by the lumbar and cervical spines. Sacral involvement is rare. [18]

ABCs of the spine usually present as expansile areas of bone remodeling in the posterior elements. Extension into the vertebral body can occur 75% of the time. The lesion may have a thin outer periosteal rim of bone, and septations within the mass may be apparent. The mass may extend into adjacent vertebrae, discs, ribs, and paravertebral soft tissues.

The bone scan exhibits peripheral increased uptake with a central "cold area" creating a donut sign. If angiography is performed, the mass is found to be hypervascular 75% of the time. CT and MRI are used to confirm the cystic nature of the lesion as well as the tumor extension into surrounding tissues and the tumor's relationship to the spinal canal. Single or multiple fluid/fluid levels sometimes can be visualized on MRI. MRI with gadolinium demonstrates enhancement of the periosteal rim and septations and not the cystic spaces.

ABCs are characteristically multiloculated blood-filled spaces that are not lined by endothelium. They are not vascular channels. Primary ABCs are believed to result from microtrauma to the bone with local circulatory disturbance. Other underlying neoplasms, such as giant cell tumors (GCTs), osteoblastomas, chondroblastomas, or osteosarcomas, produce secondary ABCs. These other neoplasms produce venous obstruction and possible arteriovenous malformations and set the stage for ABC formation. Most ABCs are considered primary (65-95%).

Because of the locally aggressive behavior of spinal ABCs, their treatment can be problematic. The severe morbidity that can be associated with complete resection is caused generally by danger to surrounding vascular or neural elements. ABCs can have a recurrence rate of 20-30% or higher, depending on the degree of resection. Preoperative embolization therapy and radiation may help shrink the tumor's size and decrease the amount of intraoperative blood loss associated with resection.


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