ACTA1 and neoplasm: As for the fate of donor-derived αSMA(+) SCSSNs, we hypothesize that donor-derived αSMA(−) SCSSN entered the cytoplasm of αSMA(+)SCSSNs (false positive), (2) donor-derived bone marrow stromal cells engrafted in a region other than the ilium were recruited to the tumor site, and (3) the possibility of cell fusion could not be completely ruled out.