Periosteal Osteosarcoma

**Semantic type:** Neoplastic Process

**Definition:** An intermediate grade malignant bone-forming mesenchymal neoplasm with chondroblastic differentiation. It arises from the surface of the bone and affects the diaphysis or diaphyseal- metaphyseal portion of the long bones. A painless mass or swelling is the most common clinical sign. It is associated with a better prognosis than conventional osteosarcoma.

**Synonyms:** - Juxtacortical Chondroblastic Osteosarcoma - Periosteal osteosarcoma - Surface Periosteal