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Osteosarcoma is the most common malignant primary bone tumor. Osteosarcoma tends to occur in children and young adults typically 10-25 or 30 years of age. Osteosarcomas also tend to occur in patients in the sixth decade, likely related to malignant degeneration of Paget's disease. It is said that they tend to occur most often towards the end of long bones in the metaphyseal region but they can also arise in the diaphysis and there is enough variation that this parameter is not terribly helpful in differentiation. A typical osteosarcoma is destructive with associated sclerosis from either malignant bone formation or reactive sclerosis. There are multiple types of osteosarcoma. The most common of which is the Conventional Osteosarcoma which accounts for 75% of cases. Conventional osteosarcoma is typically located around the knee and is a very aggressive lesion associated with a soft tissue mass, cortical destruction, a permeative pattern of bone change. Most demonstrate some degree of osteoid matrix. Conventional osteosarcomas commonly arise in the metadiaphysis but regularly (75%) cross the physis to involve the epiphysis. The distal femur and proximal tibia are the bones most commonly involved, followed by the humerus and iliac wing. They have a rapid doubling rate, are often large when discovered and are aggressive in appearance. Lesions are typically permeative with a wide zone of transition. Cortical breakthrough can be seen typically with a large soft tissue mass. Periosteal reaction typically presents with a Codmanâ€™s triangle or sunburst pattern. At least 90% of conventional osteosarcomas produce osteoid matrix in variable quantities which alters their radiographic appearance. Lesions that are dense appear low in signal on T1 and T2 sequences and if they are less dense, typically will be low signal on T1 and higher signal on T2 imaging.
Diagnostic Radiology/Musculoskeletal Imaging/Tumors Basic/Osteosarcoma
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Type: Reference Material
Submitted by: admin
Added: Sat Dec 02 2006
Last Modified: Thu Jul 30 2009