Radiological Review of Extremity Osteosarcoma

Introduction: Osteosarcoma is the most common primary nonhematologic bone malignancy and is the most common primary bone malignancy in children. There are various subtypes of osteosarcoma, each with distinct clinical and imaging characteristics and variable survival and an incidence of 0.2 to 0.3 per 100,000/year. Osteosarcomas can be classified as intramedullary (high grade, telangiectatic, low grade, small cell, osteosarcomatosis, gnathic), juxtacortical (parosteal, periosteal, intracortical, highgrade surface), or secondary lesions [1]. Though majority of cases are of conventional high grade intramedullary osteosarcoma accounting for 75%90%, it is important to differentiate them from other low grade and (low grade central and parosteal osteosarcoma) and intermediate grade osteosarcoma (Periosteal osteosarcoma). An understanding of the systematic imaging approach helps to more accurately diagnose these lesions and direct effective treatment. This article provides an organized approach to analyzing and subtyping of osteosarcoma based on radiographs and guiding the referring physician if any further imaging is warranted as there is frequently overlap with other benign and malignant entities, creating substantial diagnostic challenges. For accurate diagnosis, it is important to be aware of radiographic and cross-sectional imaging features that allow differentiation of each subtype of osteogenic sarcoma from its mimics. Osteosarcoma is a malignant tumor that is characterized by production of osteoid matrix (immature bone) and variable amounts of cartilage matrix and fibrous tissue [2]. Each subtype of the osteosarcoma exhibit distinct imaging features mimicking different benign and malignant entities, however with critical evaluation of specific features a correct diagnosis can be made. Furthermore, important prognostic information, as well therapeutic options can be evaluated based on imaging.