OSTEOSARCOMA - SUBTLE, RARE, AND MISLEADING PLAIN FILM FEATURES

Osteosarcoma is a malignant, mesenchymal, osteoid, and bone-forming tu mor [1-3]. In most cases, typical radiographic features clearly illust rate the aggressive bone-forming nature of the lesion. These features include long-bone metaphyseal location, mixed areas of lysis and scler osis, cortical destruction, periosteal new bone, and soft-tissue mass. However, numerous factors contribute to misleading radiographic patte rns of osteosarcoma. They include histologic law-grade, lytic, or mini mally sclerotic lesions, early detection, confinement to the intramedu llary canal, benign-appearing periosteal reaction, rare intraosseous l ocations (subchondral, diaphyseal, intracortical), and rare skeletal s ites (e.g., soft tissues, skull, ribs, tarsal bones). Secondary osteos arcomas, such as those arising from infarcts or fibrous dysplasia, may also produce a confusing radiologic picture. The purpose of this pict orial essay is to illustrate cases of osteosarcoma that proved to be d ifficult diagnostic dilemmas because of their subtle, rare, or mislead ing plain film features.