Polyostotic coexisting fibrous dysplasia and aneurysmal bone cyst of the chest wall

A case of a 39-year-old woman with a palpable mass in the right hemithorax is presented. The mass had been growing during the last 16 years. Radiographs and computed tomography showed two lesions in the right thoracic wall: the greater was in the anterior and lateral portion of the 7th rib, the minor lesion in the 6th rib costovertebral joint. Both lesions were surgically removed. Histological examination demonstrated the association of fibrous dysplasia and aneurysmal bone cyst in the two lesions. The coexistence of these two lesions supports the theory that aneurysmal bone cyst may represent a secondary change due to haemodynamic alterations of the vascular bed caused by fibrous dysplasia.