Diagnosis: Osteosarcoma
• Osteosarcoma is a malignant bone-forming neoplasm. It most commonly affects individuals in the second decade and favors the distal femur and proximal tibia.
• Osteosarcoma appears on radiograph as an ill-defined lesion with mixed radiolucencies and radiopacities in the metaphyses of long bones.
• There is frequently evidence of cortical destruction and, in most cases, soft tissue extension.
• The histologic appearance of osteosarcoma is characterized by malignant bone matrix infiltrating the bone marrow spaces between the mature trabeculae. The malignant bone is typically deposited in a lacelike pattern, encircling the neoplastic mesenchymal cells.
• After the diagnosis is confirmed by biopsy, the patient receives a full course of multidrug chemotherapy aimed at reducing the size of the tumor, making it amenable to en bloc surgical resection with allograft replacement (limb salvage procedure).
• The resection specimen is examined microscopically to determine the extent of tumor necrosis; at least 95% of necrosis indicates a good response. The postoperative chemotherapy protocol is modified accordingly.