Parosteal osteosarcoma of the humerus.

The authors report the case of a 50-year-old man who presented with nontraumatic swelling of the left upper arm. The diagnosis of parosteal osteosarcoma of the humerus was made after diagnostic workup. A long diaphyseal segment of the humerus containing the tumor was resected with a healthy margin of soft tissues and was irradiated extracorporeally with a single dose of 30 Gray. The bony segment was then reimplanted after removal of the tumor using plate and screw fixation. Loosening of the proximal screws after one year required additional fixation and autologous cancellous bone grafting. The patient has a nearly three-year-follow-up and there are no signs of tumor recurrence or metastasis. The proximal osteotomy has healed nicely; the distal fixation osteotomy exhibits delayed healing. The pathogenesis of parosteal osteosarcoma is discussed.