Primary tumours of bone are unusual, and have a characteristic age incidence. You will see: osteosarcomas, mostly in the 10 to 25 year age group, chondrosarcomas (15 to 50 years), Ewing's tumours (5 to 25 years) and giant cell tumours (15 to 50 years). Adamantinomas occasionally occur in the jaw, usually the mandible (26.7), and cordomas mainly in the sacrum (rare). Fibrosarcomas arising from the periosteum behave like fibrosarcomas of the soft tissues. Secondary deposits in bones and myelomas are more common.