Osteogenic Sarcoma (Osteosarcoma)

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Etiology/Pathophysiology:
Has a sarcomatous connective tissue stroma with osteoid and bony tumor tissue arising from this malignant stroma. Classified as osteoblastic, chondroblastic, fibroblastic depending on the predominant tissue. Primarily metastasizes to the lungs but occasionally metastasizes to other bones. Is the most common primary skeletal malignancy in children. The tumor is eccentric, usually metaphyseal, but it may extend into the epiphysis or along the medullary cavity into the diaphysis. The long bones are involved in 80-90% of the cases. The most common sites in order of frequency are the distal femur, proximal tibia, proximal fibula, and proximal humerus. May also involve flat bones like the ileum and mandible.

Pathology:
Not applicable

Imaging Findings:
On film see cortical bone destruction with lysis and sclerosis and an associated soft tissue mass with foci of calcification. Codman's triangle is the classic sign of malignant periosteal reaction.

MRI is best for establishing the medullary extent of the tumor.

Bone scan shows skeletal metastases best.

Chest CT is best at determining the presence of lung metastases.

DDX:

• Ewings sarcoma
• Osteomyelitis

References:
See References Chapter.

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