In patients younger than 20 yrs. of age, the commonest primary bone cancers are osteosarcomas (56%) and Ewing tumors (34%). Chondrosarcomas make up only about 6% of bone cancers in this group. In adults, the commonest primary bone cancer is chondrosarcoma (40%), followed by osteosarcomas (28%) and chordomas (10%) (Source: American Cancer Society; www.cancer.org). The chart shows breakdown by diagnosis of 7389 cases of primary malignant tumors of bone treated at the Rizzoli Institute, Bologna, Italy. Slide courtesy of Piero Picci, M.D., Director, Laboratory of Experimental Oncology, Instituto Ortopedico Rizzoli, Bologna, Italy. Used with permission.