Osteogenic sarcoma presents a typical radiographic picture of destructive and osteoblastic changes.
The neoplasm usually begins eccentrically in the metaphyseal region of a long bone.
Bone destruction manifests itself as a loss of normal trabecular pattern and the appearance of irregular ill-defined, poorly marginated, ragged radiolucent defects.
New bone formation may be neoplastic or reactive and appears in the form of areas of increased radiopacity.
The cortex is seen to be invaded by the growing tumor, as evidenced by destruction of the cortical wall and raising of the periosteum.
The “sunburst” appearance is produced by the formation of spicules of new bone laid down perpendicularly to the shaft along the vessels passing from the periosteum to the cortex.
Codman’s triangle has its base perpendicular to the shaft and is created by the subperiosteal reactive new bone but is not characteristic of osteogenic sarcoma, as it is also seen in osteomyelitis and Ewing’s sarcoma.
A soft-tissue mass will be discernible in the radiograms as the tumor advances further, transgressing the cortex. Pathologic fracture may occur.
Linear tomography and computed tomography are of great value in depicting the details of bone destruction and tumor bone production within the lesion.
The neoplastic bone is amorphous and not stress oriented. The areas of cortical erosion by the tumor tissue are well delineated. The degree of soft-tissue extension and the relationship of the extra-compartmental tumor to fascialo planes is clearly demonstrated by the CT scan.
Occult skip metastases of 2 mm. or more in diameter are identified by CT scan.
Conventional radiograph of the chest (dual inspiration and expiration views) will detect metastatic nodules 10 mm. or greater in diameter; ordinary tomography will demonstrate metastatic lesions between 5 and 10 mm.
Bone scan with technetium-99m will show marked increase in the uptake of the radionuclide due to active formation of new tumor bone. The vascularity of the lesion augments the intensity of the uptake.
Angiography is of great value in delineating the extent of soft-tissue extension and its relationship to adjacent neurovascular structures. The early arterial phase demonstrates the reactive neovasculature awhereas the late venous phase shows the intrinsic vascularity.
Angiography is of particular value when limb salvage is being combined with radical ablation of osteogenic sarcoma.
Laboratory Findings
The serum alkaline phosphatase level is elevated in osteosarcoma which varies with the activity of the neoplastic osteoblasts within the lesion and the size of the tumor.
An immunologic findings in osteogenic sarcoma is the presence of antisarcoma antibody in the serum.
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