Aneurysmal Bone Cysts of Soft Tissue Represent True Neoplasms

Abstract

Aneurysmal bone cyst was first described by Jaffe and Lichtenstein in 19421. It is considered a benign, locally aggressive lesion with a potential for local recurrence, and it typically appears in the metaphysis of the long bones and in the vertebral column2-4. Mostly, children and young adults are affected. No sex predilection has been observed. Radiographically, aneurysmal bone cyst is seen as a lytic lesion, usually eccentrically located and expansile but with well-defined margins. Histologically, there are blood-filled cysts separated by fibrous septa, with fibroblasts as well as osteoclast-type giant cells and reactive woven bone5. Historically, aneurysmal bone cyst was believed to occur exclusively in bone6. In 1972, Salm and Sissons noted soft-tissue lesions resembling aneurysmal bone cysts, and this was probably the first description of this entity7. For many years, aneurysmal bone cyst was thought to be a lesion, reactive in nature, caused by a circulatory abnormality leading to an increased venous pressure and resulting in dilation of the vascular network2,8,9. In recent years, strong evidence has supported the neoplastic nature of aneurysmal bone cyst10-13. In 1999, Panoutsakopoulos et al.10 demonstrated chromosomal translocation t(16;17)(q22;p13) as a recurrent cytogenetic abnormality in primary aneurysmal bone cyst, which was confirmed by other groups11-13. We report two cases of soft-tissue aneurysmal bone cyst with USP6 locus rearrangement on chromosome 17p13. The patients were informed that data concerning their cases would be submitted for publication, and they consented. Tissue specimens from two cases of primary soft-tissue aneurysmal bone cyst were collected in 2007, fixed in 5% buffered formalin, and processed in standard fashion after decalcification, and micrometer sections were prepared with hematoxylin and eosin staining. The histological …