An aneurysmal bone cyst is a non-neoplastic, Adestructive and expansile lesion consisting of a "blood-filled sponge" that is defined to represent a benign reactive vascularity.1-3 Szendroi et al4 suggested that the aneurysmal bone cyst corresponds to a haemodynamic disturbance that is primary or secondary venous malformation of the bones. The association with trauma including fracture has also been noted and 25%-71% of such patients have a history of trauma.57 Conventionally, malignant transformation of aneurysmal bone cysts is perceived as a rare occurrence except those induced by irradiation.8-10~ Both malignant fibrous histiocytoma and osteosarcoma have been reported in the malignant transformation cases.