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Radiographic Features of Bone Tumors

- See:
    - Outside Links: Approaches To Differential Diagnosis In Musculoskeletal Imaging:
               - Soft Tissue Calcifications
               - Lucent Lesions of Bone
               - Sclerotic Lesions

- Discussion:
    - note whether the bone formed in tumor is being produced by actual tumor cells or by normal osteoblasts reacting to tumor;
    - while several benign tumors may form bone, only osteogenic sarcoma is a malignant bone forming tumor;
    - host bone often responds to a tumor by combination of resorption and bone formation;
    - reactive bone that forms the thin sclerotic border of slowly growing tumor may be mature lamellar bone;
    - some tumors, such as typical osteochondroma, are so characteristic that x-rays alone can establish the dx;
    - in case of most bone tumors, and particularly those that destroy bone, dx cannot be established by roentgenographic means alone;
    - location of tumors:
          - some tumors are found only in epiphysis, whereas others are most frequently seen in the metaphysis;
          - smaller number are encountered in the diaphyseal region;
          - some lesions occur most frequently before epiphyseal closure, whereas others are seen only after the epiphyses have closed;
    - ragiographic features:
          - benign lesions are suggested if tumor is limited to the confines of bone, if it has well-demarcated
                 border surrounded by a thin rim of sclerotic bone, and if it has not broken through the cortex;
          - malignant lesions:
                 - are suggested if the boundaries of the tumor are ill-defined, if there are no sharp borders, if the lesion has a mottled appearance,
                         and if it has broken out of the confines of the bone and destroyed cortex, malignancy is to be suspected;
                 - malignant tumor cells that extend through the cortex may elevate periosteum and stimulate it to produce a small triangle of 
                        reactive bone (Codman's triangle) where periosteum is lifted from the shaft;
                        - seen in osteosarcoma and Ewing's sarcoma but can also be found in infections and hemorrhagic lesions;
                 - formation of new osseous tissue outside involved bone is suggestive of malignancy but can also be found in cases of infection
                        and in myositis ossificans;
                 - small bony spicules radiating in a direction perpendicular to shaft, sunray effect, are frequently found in osteogenic sarcoma but 
                        may be caused by other malignant, and even by some benign, processes;
                 - subperiosteal new bone formation, which has laminated or onionskin appearance, is seen in Ewing's sarcoma, but it may also be 
                        found in other conditions that elevate periosteum, such as infection

Magnetic resonance imaging in planning limb-salvage surgery for primary malignant tumors of bone.