<unk>  has been widely regarded a reactive process of uncertain cause since its initial description by Jaffe and Lichtenstein in 1942. Many hypotheses have been proposed to explain the cause and pathogenesis of<unk> , and until very recently the most commonly accepted idea was that<unk>  was the consequence of an increased venous pressure and resultant dilation and rupture of the local vascular network. However, studies by Panoutsakopoulus et al. and Oliveira et al. uncovered the clonal neoplastic nature of<unk> . Primary cause has been regarded arteriovenous fistula within bone. The lesion may arise de novo or may arise secondarily within a pre-existing bone tumor, because the abnormal bone causes changes in hemodynamics. An<unk>  can arise from a pre-existing chondroblastoma, a chondromyxoid fibroma, an osteoblastoma, a giant cell tumor, or fibrous dysplasia. A giant cell tumor is the most common cause, occurring in 19% to 39% of cases. Less frequently, it results from some malignant tumors, such as osteosarcoma, chondrosarcoma, and hemangioendothelioma.
Aneurysmal bone cyst
Bone cyst
Osteoid osteoma
Unicameral bone cyst
Juvenile active ossifying fibroma
Osteoma
Osteochondroma
Peripheral ossifying fibroma