A three-year-old male neutered Irish setter is presented with a two-week history of lameness with a one-week history of swelling of the distal right forelimb.
A radiograph of the affected area is shown below.
What is the presumptive diagnosis?
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This is a classic image of osteosarcoma, a common, aggressive bone tumor typically found in the appendicular skeleton, especially distal radius.
Here is a memory aid for common locations of osteosarcoma – “Away from the elbow, near the knee.”
90% have microscopic metastases to lungs by time of Dx (but less than 10% will have visible thoracic metastasis at time of diagnosis).
Usually, does not cross joint (unlike osteomyelitis, which usually does cross joint). Look for soft tissue swelling, periosteal proliferation, sunburst periosteal reaction (33%), possible pathologic fractures.
