Regression of aneurysmal bone cyst following open biopsy

Aneurysmal bone cysts are well described but relatively rare bone lesions. Histological diagnosis is usually obtained before definitive treatment. We report a patient with aneurysmal bone cyst regression after excisional biopsy and prior to preoperative embolization. This was also a patient with the William syndrome. This has not previously been reported, nor is there any known association between aneurysmal bone cyst and the William syndrome.