Aneurysmal Bone Cysts (ABCs)

Study Notes

ABCs are benign tumors that typically affect patients younger than 20 years, with a slight female preponderance.
ABCs typically arise from long bones, but about 12% to 30% of cases involve the spine.
CT and MRI are the most useful imaging techniques for the assessment of ABCs.
CT shows expansile, osteolytic, and cystic lesions surrounded by thin layers of reactive cortical bone (“eggshells”), and MRI shows heterogeneous signals denoting the various hemoglobin degradation products present.
Histologically, ABCs show cystic cavities filled with blood products separated by fibrous septa. They are expansile and, as on imaging, are associated with significant bony destruction with thin layers of reactive cortical bone surrounding them.
Although the majority of ABCs are primary lesions, they can also be secondary lesions associated with other spinal tumors, including GCT, osteoblastoma, chondroblastoma, and osteogenic sarcoma.
Embolization is the treatment of choice for ABCs, and several successful cures have been reported after embolization.
Surgically, complete excision of the tumor is the goal but may be difficult. Incomplete tumor excision may be associated with significant rates of tumor recurrence.
ABCs are sensitive to radiation, but the recurrence rate remains significant despite adjuvant radiotherapy.
In addition, radiation therapy in young patients with ABCs raises concern about the development of radiation-induced sarcomas in the future.

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