Aneurysmal bone cyst: rapid deterioration in a long-standing tumor.

Aneurysmal bone cyst, first described by Jaffe and Lichtenstein I in 1942 as a rare, localized tumor of the long bones and spinal vertebrae, characterized by the "blowout distention" of the skeletal contour on a radiograph.2 This neoplasm, usually found in children and young adults, constitutes 1.4 percent of all primary bone tumors.3 The cyst is occasionally associated with other tumors of the bone, such as osteoblastoma, osteosarcoma, giant cell tumor, and fibrous dysplasia,4 and has occasionally been reported to occur at a site of previous trauma to the bone.5 There is a tendency toward rapid growth with local expansion, which can exert pressure on an adjacent structure. 3 Histologically, aneurysmal bone cyst is a cystic, osteolytic vascular tumor, replete with giant cells and fibrous septa. The tumor has a solid variant with fibroblastic proliferation, giant cell areas, stromal hemorrhage, and new bone production.6 When an aneurysmal bone cyst appears in the spine, it is generally diagnosed within a few months after the onset of clinical symptoms, which include local pain and swelling accompanied by reactive local muscle stiffness and restriction of movement. Only in advanced and rare cases does the aneurysmal bone cyst exert pressure on the spinal cord, which can lead to neurologic deficits.6,7 We describe the diagnosis, management, and follow-up of an aneurysmal bone cyst in a 14-year-old girl.