Nonradiopaque penetrating foreign body: "a sticky situation".

Foreign bodies within soft tissues are common in children. They may cause a chronic inflammatory reaction that can result in abnormal findings on radiographs, including lytic or blastic osseous changes. These radiographic findings can mimic both benign and malignant processes. In cases where the history is uncertain and the foreign body is not recognized, magnetic resonance (MR) imaging can make a specific diagnosis and direct appropriate therapy.