Aneurysmal Bone Cyst of the Clavicle: A Case Report

INTRODUCTION: Aneurysmal bone cyst is a rare benign solitary tumor of the long tubular bones, pelvis, and vertebrae which rarely affects the clavicle. It is common in the adolescent age group and rare in old age. The characteristic radiological suggests and histopathological picture confirms its diagnosis. This case is of interest because there are only a few cases of aneurysmal bone cyst of the clavicle reported to date. CASE REPORT: An 11-year-old boy presented with a history of pain in the right clavicular area for 3 months associated with swelling which gradually increased in size. The radiograph showed an expansile bony mass at the lateral fourth of the right clavicle with internal septations with thinning of the cortex and no evidence of periosteal reaction. The affected part of the lateral part of the clavicle was resected leaving the thick periosteum intact. Histologically, section revealed solid and cystic areas. The cysts were separated by septa and filled with hemorrhage and beneath the surface showed osteoid bone formation and multinucleated giant cells. Stroma showed loosely arranged spindle cells which had vesicular nuclei, inconspicuous to prominent nucleoli, and moderate amount of eosinophilic cytoplasm. Prominent blood vessel proliferation was evident. Pleomorphism and mitotic figures were not seen in the specimen. The overall histological picture was that of an aneurysmal bone cyst. CONCLUSION: Aneurysmal bone cyst occurring in this age group is not so common in the clavicle. This is a rare case which requires mention in literature. Our case was treated by marginal resection. On regular follow-up,the regeneration of the bone within the intact periosteum can be seen.