Telangiectatic dedifferentiation of a parosteal osteosarcoma

A unique case of parosteal osteosarcoma (POS) of the proximal femur, with a reas of telangiectatic dedifferentiation, in a 28-year-old woman is reporte d. The patient had a 7-week history of pain and swelling in her right thigh . A biopsy diagnosis of POS was established. The patient was treated with t wo cycles of intraarterial chemotherapy, followed by limb salvage surgery. Histological examination of the resected specimen showed POS with areas of dedifferentiation composed of high-grade telangiectatic osteosarcoma with a ssociated secondary aneurysmal bone cyst change.