FOXC2 and Ewing sarcoma: While positive FOXC2 immunostaining was observed in 3 of 7 Ewing's sarcomas and 1 of 2 embryonal rhabdomyosarcomas, 9 of 10 examined osteosarcomas were positive for FOXC2 with 7 tumors exhibiting strong staining and the remaining 2 tumors exhibiting weak staining (Supplementary Table S1).