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This 14-year-old white male first experienced mild pain in the left knee after playing baseball, approximately two months prior to admissionago. The pain persisted in an intermittent fashion, and was described as being somewhat worse at night. Approximately until approximately two weeks prior to admission, when the pain increased significantly and was accompanied by marked swelling and loss of considerable motion of the knee joint. These symptoms were accompanied by a history of He also had decreased appetite, lethargy, and a 10-pound weight loss. On physical examination, the left knee was enlarged diffusely, firm, and non-tender. Following Radiographic and biopsy, the results confirmed a diagnosis of osteosarcoma. The patient was subjected to underwent surgical removal of the distal femur and knee with placement of a prosthetic knee joint and bone grafts.

== Autopsy Findings ==The distal diaphysis of the femur and adjacent soft tissues were involved in a 15 x 10 x 10-cm mass. The cut surface of the mass was fleshy white, with focal areas of hemorrhage.

File:IPLab7Osteosarcoma7IPLab7Osteosarcoma7b.jpg|This is a photomicrograph of a decalcified histologic section from normal bone. Compare this normal morphology to the subsequent images of bone in this case of osteosarcoma.File:IPLab7Osteosarcoma8b.jpg|This is a higher-power photomicrograph of decalcified histologic section from this tumor. There are areas of osteoid (1) and cellular areas (2).File:IPLab7Osteosarcoma8IPLab7Osteosarcoma9b.jpg|This is a highhigher-power photomicrograph of decalcified histologic section showing the cellularity of the tumor. File:IPLab7Osteosarcoma9IPLab7Osteosarcoma10b.jpg|This highhigher-power photomicrograph demonstrates the cellular growth pattern. Note that the cells are fusiform pleomorphic and they grow in sheetsanaplastic. File:IPLab7Osteosarcoma10IPLab7Osteosarcoma11b.jpg|This high-power photomicrograph demonstrates the growth pattern and the cell morphology. File:IPLab7Osteosarcoma11.jpg|This is a high-power photomicrograph of the tumor cell morphology and the periosteum (arrow). File:IPLab7Osteosarcoma12.jpg|This high-power photomicrograph of the tumor demonstrates the fusiform morphology of the cells. Note the marked variability in size and staining intensity of the nuclei. File:IPLab7Osteosarcoma13.jpg|This is a high-power photomicrograph of the tumor demonstrating the anaplastic cell morphology. File:IPLab7Osteosarcoma14.jpg|This is a high-power photomicrograph of the tumor demonstrating the anaplastic cell morphology. File:IPLab7Osteosarcoma15IPLab7Osteosarcoma12b.jpg|This is a high-power photomicrograph of the tumor demonstrating the anaplastic cell morphology and multiple mitotic figures (arrows).