Aneurysmal bone cyst associated with fibrous dysplasia of the skull.

A 25 year old patient presented with a post-traumatic soft tissue swelling of the occiput, overlying an area of bone expansion and destruction. At operation an aneurysmal bone cyst was found. 11 years previously a similar parietal lesion had been found in conjunction with fibrous dysplasia. The differential diagnosis and treatment of this entity is discussed.