Osteosarcoma

Conventional osteosarcoma (85%)

• Intramedullary mass, extends through cortex
• Sunburst periosteal reaction

Telangiectatic osteosarcoma (< 5%)

• Lytic lesion with cystic cavities

Multicentric osteosarcoma (1%)

• Multiple sites (usually symmetric)
• Only in children (5-10 years)
• Extremely poor prognosis

Parosteal osteosarcoma (3%)

• Older age group (20 - 50 years)
• Classically posterior distal femur
• Attached to underlying cortex at origin (broccoli appearance on CT)

Periosteal osteosarcoma (1%)

• Intermediate-grade
• Diaphyseal
• No medullary involvement
• Cortical thickening

Gnathic osteosarcoma (5-9%) Originates in mandible or maxilla

Secondary osteosarcoma (5%)

• Association with Paget disease, prior radiation, bone infarct, etc

Differential

• Myositis ossificans - ossifies from out to in (lucent center) unlike osteosarcoma