Compared with normal tissues, B7-H3 is overexpressed in a variety of pediatric solid tumors, including neuroblastoma (1–5), rhabdomyosarcoma (3, 5–7), osteosarcoma (5, 8), Ewing sarcoma (5, 6), Wilms tumor (5), and desmoplastic small round cell tumor (4, 5), as well as in a number of cancers more common in adults (9–13). This evidence concerns the gene CD276 and Ewing sarcoma.