High malignant surface osteosarcoma arising at the site of a previously treated aneurysmal bone cyst.

A patient who developed a high malignant surface osteosarcoma at the site of a previously treated aneurysmal bone cyst is reported. The patient developed the osteosarcoma 4 years after complete curettage and bone-grafting of the cyst. The clinical, radiological and light microscopic features of this case are described. A causal relationship between the preexisting aneurysmal bone cyst and osteosarcoma is discussed, but seems to be unlikely.