Cysts

Abstract

The primary cystic lesions in bone include aneurysmal bone cysts, unicameral bone cysts, and, rarely, intraosseus ganglion cysts. Aneurysmal bone cyst is a rapidly growing, locally destructive lesion that affects all age groups and may affect any bone. It occurs more commonly during the first two decades of life. Most aneurysmal bone cysts occur in the metaphysis of long bones, followed by the posterior elements of vertebral bodies. Traditionally regarded as a reactive process, it now is generally accepted that primary aneurysmal bone cysts are neoplastic in nature, given that a significant proportion of cases demonstrate recurrent chromosomal alterations resulting in rearrangements of the USP6 gene on the short arm of chromosome 17, whereas these cytogenetic abnormalities are absent in all secondary aneurysmal bone cysts, that is, those associated with another primary tumor, such as giant cell tumor of bone. Unicameral bone cyst, also known as simple bone cyst or solitary bone cyst, likewise commonly affects skeletally immature individuals, but is considered likely to be reactive or developmental in nature. An intraosseous ganglion cyst almost always occurs at the ends of long bones, and appears to be connected to the nearby joint.