Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 53 2 2015 02 15 139 142 EN Khodamorad Jamshidi Department of Orthopedic Surgery, Shafa Yahyaian Rehabilitation Center, Iran University of Medical Sciences, Tehran, Iran. Farid Najd Mazhar Department of Orthopedic Surgery, Shafa Yahyaian Rehabilitation Center, Iran University of Medical Sciences, Tehran, Iran. Reza Shafipour Department of Orthopedic Surgery, Shafa Yahyaian Rehabilitation Center, Iran University of Medical Sciences, Tehran, Iran. 2015 10 11 Aneurysmal bone cyst (ABC) is blood filled expansile cystic lesion that most commonly occurs in patients during the second decade of their lives. Traditionally it has been described as a benign lesion but can be locally aggressive and result in the destruction of the involved bone. Treatment methods include surgical excision and curettage with or without bone grafting. We report a proximal femur aneurysmal bone cyst, which resulted in the amputation of the lower extremity, even though all available classic methods of treatment were applied for it. https://acta.tums.ac.ir/index.php/acta/article/view/4921 https://acta.tums.ac.ir/index.php/acta/article/download/4921/4328