CD99 and neoplasm: Cells were immortalized through sequential passaging, and their tumorigenicity capacity was confirmed when inoculated into NSG mice, while preserving the tumor characteristics, as indicated by monolayer culture and markers of immunofluorescence analysis such as MDM2, SMA, Desmin, CD99, CD44, Myogenin, S-100, and CK, as depicted in Figure 5A,B.