Imaging of bone tumors plays an important role in the diagnosis, not only can it show the exact location, size, adjacent bones and soft tissue changes of the tumor, but also can determine whether it is benign or malignant, primary or metastatic in most cases. All bone tumors have a tendency to occur at a certain age. Osteosarcoma is more common in adolescents aged 15-25 years (75%). Ewing’s sarcoma is most often seen in the age of 30 years or less and 10-15 years (40%). Giant cell tumors of bone tend to occur after epiphyseal fusion (20-40 years of age). Fibrosarcoma and chondrosarcoma are most often seen in young adults over 30 years of age. Metastases and myeloma are more common in middle-aged and older adults. Osteosarcoma Histology Osteosarcoma (osteosarcoma), also known as osteogenic sarcoma or osteogenic sarcoma, originates from the mesenchymal tissue of undifferentiated bone. The tumor cells can form osteoid tissue and bone directly, as well as fibrous and cartilaginous tissue, and the cartilage can ossify into tumor bone. Imaging manifestations of osteosarcoma Basic X-ray manifestations Tumor bone forms ivory-like (well differentiated tumor osteoblasts), cotton wool-like (poorly differentiated tumor osteoblasts form naive bone and bone-like tissue), and needle-like (tumor breaks through the bone cortex and tumor cells next to the bone form needle-like bone perpendicular to the bone cortex). The lesser the tumor bone component, the higher the malignancy. Bone destruction worm-like, patchy bone defects with sieve-like, interrupted or mutilated cortical destruction (osteolytic destruction; also non-destructive, spreading along the bone marrow without destroying bone trabeculae; also spreading outward along the Harvard canal without destroying the bone cortex). The periosteal reaction is laminar, needle-like or radial, and the periosteal triangle (Codman’s triangle) is present in about 70% of cases. The thicker the periosteal reaction and the more layers there are, the more rapidly the tumor grows and develops. Soft tissue masses with calcification of tumor bone or tumor cartilage are common.