Spontaneous healing of aneurysmal bone cysts. A report of three cases.

We report three cases of spontaneous healing of aneurysmal bone cysts (ABC). In one case histological material was obtained after resection of the already ossified expansile mass discovered as a lytic lesion seven months previously. In the two other patients, spontaneous ossification of a radiologically presumed ABC in the lytic and expansile phase was observed after nine and seven months respectively. The healed lesions have remained stable at 12, 32, and 36 months respectively. These findings suggest that when the diagnosis can be made with confidence, and the lesion is in a location and at a stage that does not entail any risk of fracture or compression, expectant management should be considered. Our three patients were aged 22, 19 and 18 years, older than usual for developing ABC. This is also true for many of the few other reported cases of spontaneous or almost spontaneous healing and suggests that ABC has a greater tendency to stabilise in older patients.