In the intraosseous tumors formed by SiRb‐OeMyc cells, osteoid tissue, cells that tested positive for ALP, osteonectin, and osteocalcin, and cells that tested slightly positive for desmin and α‐SMA were detected, but no cells that tested positive for PPARγ, h‐caldesmon, FLI‐1, and S100, which indicates that tumors that are formed by SiRb‐OeMyc are OS, but are not likely to be leiomyosarcoma, liposarcoma, Ewing tumor, or chondrosarcoma. The gene discussed is ACTA1; the disease is leiomyosarcoma.