Aneurysmal Bone Cyst Arising from the First Rib: A Rare Cause of Thoracic Outlet Syndrome.

Aneurysmal bone cyst is a rare benign cystic bone lesion with an incidence of only 0.14 per 100,000 individuals and most commonly affects the metaphyses of long bones, spine, and pelvis. We present a very rare case of a 17-year-old boy with a rapidly expanding aneurysmal bone cyst arising from the first rib, resulting in neurogenic thoracic outlet syndrome secondary to its compression of the brachial plexus. The patient's symptoms resolved after en bloc resection. To our knowledge there have been no other reports in the literature of thoracic outlet syndrome due to aneurysmal bone cyst arising from the first rib.