Osteosarcoma is the most common type of malignant bone cancer, accounting for 35% of primary bone malignancies. There is a preference for the metaphyseal region of tubular long bones. 50% of cases occur around the knee. It is a malignant connective (soft) tissue tumor whose neoplastic cells present osteoblastic differentiation and form tumoral bone.
Diagnosis
Family physicians and orthopedists rarely see a malignant bone tumor (most bone tumors are benign). Thus, many patients are initially misdiagnosed with cysts or muscle problems, and some are sent straight to physical therapy without an x-ray.
The route to osteosarcoma diagnosis usually begins with an x-ray, continues with a combination of scans ( CT scan, PET scan, bone scan, MRI) and ends with a surgical biopsy. Films are suggestive, but bone biopsy is the only definitive method to determine whether a tumor is malignant or benign.
The biopsy of suspected osteosarcoma should be performed by a qualified orthopedic oncologist. The American Cancer Society states: "Probably in no other cancer is it as important to perform this procedure properly. An improperly performed biopsy may make it difficult to save the affected limb from amputation."
Anteroposterior radiograph and (B) lateral radiograph showing a destructive lesion in the metaphysis of the femur with a small amount of fluffy mineralisation and thick periosteal reactions.
Anteroposterior radiograph shows mixed lytic and sclerotic lesion of right fibular head and periosteal reaction on medial fibular neck and shaft. 
osteosarcoma of distal tibia. Anteroposterior radiograph shows primary tumor
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