Etymed
osteosarcoma
Definition
A primary malignant bone tumor characterized by the direct formation of osteoid or immature bone by tumor cells. It is the most common primary malignant bone tumor in adolescents and young adults, typically arising in the metaphysis of long bones.
Clinical context
A 16-year-old male presents with a 3-month history of progressive right knee pain and swelling that worsens at night and is not relieved by rest. Physical examination reveals a firm, tender mass over the distal femur. X-ray shows a destructive lesion in the distal femoral metaphysis with a periosteal "sunburst" pattern and Codman triangle. MRI reveals marrow replacement with soft tissue extension. Serum alkaline phosphatase and LDH are elevated. Core needle biopsy confirms high-grade osteosarcoma with osteoid production by malignant cells. Staging shows no pulmonary metastases. He begins neoadjuvant chemotherapy (MAP: methotrexate, doxorubicin, cisplatin) followed by limb-salvage surgery.
Mnemonic
OSTEO (bone) + SARC (flesh) + OMA (tumor) = fleshy tumor of bone. The tumor makes malignant osteoid — think of the "sunburst" on X-ray as malignant bone bursting through periosteum.