DEDIFFERENTIATED PAROSTEAL OSTEOSARCOMA OF THE RADIUS

A 35-year-old woman presented with a painful swelling in the left dist al radius that had been present for 1 year. Radiography and computeriz ed tomography revealed a sclerotic surface lesion that had grown over the year and eroded the cortex. Histological examination demonstrated two distinct components: a cartilaginous low- to moderate-grade osteos arcoma on the surface and a high-grade osteosarcoma in the intramedull ary component. This case is uncommon in two aspects: the radius is a r are site for such a tumor and the dedifferentiation was revealed at th e time of the first surgery and was not secondary to recurrence.