Osteosarcoma appearing as a pathologic fracture.

Osteosarcoma is the most frequent primary malignant bone tumor. It usually occurs in the second decade of life. Pathologic fracture as the primary manifestation of an osteosarcoma is rather unusual, especially under the age of 10. The authors present the case of a 9-year-old boy with a diaphyso-metaphyseal femoral fracture, in whom the radiological features of an osteosarcoma were not recognized at the time of the fracture as they were not clearly visible, and at follow-up initially were considered as proliferative callus formation.