[A case of aneurysmal bone cyst arising from the left first rib].

A 30 year-old female was admitted to our department because of an abnormal chest radiograph. The chest CT scan revealed a tumor expanding from the left first rib. The tumor was resected through a left posterolateral thoracotomy. Histological findings showed aneurysmal bone cyst. Aneurysmal bone cyst is an uncommon lesion, especially in the rib. The patient's postoperative course was uneventful and there has been no evidence of recurrence during the 15 months since operation.